Scientific Report 2011 - Lorentz Center · Image by Anja van de Stolpe. Design: SuperNova Studios,...

Scientific Report 2011

Lorentz Center Niels Bohrweg 2 2333 CA Leiden The Netherlands +31 71 527 5400 [email protected] www.lorentzcenter.nl

Cover: The image was used for the announcement poster of the workshop 'Circulating Tumor Cell Isolation and Diagnostics' that was held in the Lorentz Center in February 2011. The image depicts tumors cells (yellow) among many non-tumorigenic white blood cells (gray) in a blood sample taken from a cancer patient. The aberrant tumor cell is seen enlarged in a microscopic view at the bottom-right corner. Image by Anja van de Stolpe. Design: SuperNova Studios, Delft Printing: Druk.Tan Heck, Delft

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Contents Preface by the Director v Mission Statement ix Scientific Advisory Boards xi Scientific Reports: January 17 - 21 Landing Sites for Exploration Missions Agustin Chicarro, Roderik Koenders, Tanja Zegers 1 January 24 - 28 Physics of Mixing Julyan Cartwright, Herman Clercx, Gert-Jan van Heijst, Michel Speetjens 3 January 31 - February 3 New Biology and Society: Opportunities, Challenges and Myths Roel van Driel, Tsjalling Swierstra, Johan Braeckman 5 February 7 - 11 Circulating Tumor Cell Isolation and Diagnostics Klaus Pantel, Stefan Sleijfer, Anja van de Stolpe, Leon Terstappen, Jaap den Toonder 7 February 14 - 18 Multiscale Fluid Dynamics with the Lattice Boltzmann Method Herman Clercx, Jens Harting, Sauro Succi, Federico Toschi 9 February 21 - 25 Probing the Radio Continuum Universe with SKA Pathfinders Ray Norris, Huub Röttgering 11 February 28 - March 4 Herschel and the Characteristics of Dust in Galaxies Frank Israel, Xander Tielens 13 March 7 - 11 Modeling Natural and Artificial Photosynthesis Francesco Buda, Markus Reiher, Lucas Visscher 14 March 14 - 18 Cosmic Ray Interactions: Bridging High and Low Energy Astrophysics Sera Markoff, Jesus Martin-Pintado, Diego Torres, Jacco Vink, Farhad Yusef-Zadeh 15 March 21 - 25 Control of Burning Plasmas Tony Donne, Barry Koren, Jo Lister, Didier Mazon, Pieter Nuij, Maarten Steinbuch 17 March 28 - April 1 Beam Shifts: Analogies Between Light and Matter Waves Andrea Aiello, Konstantin Bliokh, Eric Eliel, Jörg Götte, Victor de Haan, Wolfgang Löffler, Henning Schomerus 19

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April 4 - 8 100th Anniversary of Superconductivity: Hot Topics and Future Directions Mark Golden, Dirk van der Marel, Kosmas Prassides, Anne de Visser, Jan Zaanen 21 April 11 - 15 Advanced Magnetohydrodynamics Hans Goedbloed, Rony Keppens, Stefaan Poedts, Alexander Voegler 23 April 18 - 21 Quantitative Methods in Financial and Insurance Mathematics Karel in 't Hout, Cornelis Oosterlee 25 April 26 - 29 Science Meets Justice: Forensic Statistics at the Interface Richard Gill, Hans Nijboer 27 May 2 - 6 Workweek: Towards Understanding Imaging Data from LOFAR Roberto Pizzo, Huub Röttgering 29 May 9 - 13 Spin Caloritronics III Gerrit Bauer, Sadamichi Maekawa 31 May 16 - 20 Coherent Structures in Dynamical Systems Francisco Beron Vera, Henk Broer, María Olascoaga, Thomas Peacock 32 May 23 - 27 The Motivic Fundamental Group Spencer Bloch, Dale Husemöller, Jan Stienstra 33 May 30 - June 2 Molecular Logic Francois Remacle, Sven Rogge, Itamar Willner 34 June 6 - 10 4th European Women in Mathematics Summer School Dion Coumans, Andrea Hofmann, Janne Kool, Erwin Torreao Dassen 35 June 14 - 17 Black Hole Answers for Condensed Matter Questions Sean Hartnoll, Sung Sik Lee, Hong Liu, John McGreevy, Koenraad Schalm, Jan Zaanen 37 June 20 - 24 Fluctuations and Response in Active Materials: From Driven Granular Systems to Swarming Bacteria Bulbul Chakraborty, Martin van Hecke, Jean-Francois Joanny, Narayanan Menon, Corey O’Hern, Sriram Ramaswamy, Madan Rao 38 June 27 - July 1 Analysis and Visualization of Moving Objects Ross Purves, Judy Shamoun-Baranes, Bettina Speckmann, Daniel Weiskopf 40

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July 4 - 8 Extreme Value Statistics in Mathematics, Physics and Beyond Yan Fyodorov, Frank den Hollander, Sergei Nechaev, Holger Rootzen, Senya Shlosman 43 July 11 - 15 Transgenes Going Wild? Risk Assessment of Transgene Introgression from Crops into Wild Relatives Detlef Bartsch, Hans Bergmans, Patsy Haccou, Tom de Jong, Bao-Rong Lu, Jun Rong, Geert De Snoo, Allison Snow 45 July 18 - 22 Discrete Integrable Systems Peter van der Kamp, Frank Nijhoff, Reinout Quispel, Jan Sanders 47 July 25 - 29 Groups and Clusters of Galaxies: Confronting Theory with Observations Arif Babul, Graham Smith, Christoph Pfrommer, Henk Hoekstra Report not available August 8 - 12 Computational Neuroscience and the Dynamics of Disease States Stephen Coombes, Stephan van Gils, Michel van Putten, Wytse Wadman 48 August 15 - 19 Standards in Emotion Modeling Tibor Bosse, Joost Broekens, Stacy Marsella 49 August 22 - 26 Strongly Disordered Superconductors and Electronic Segregation Mikhail Feigel'man, Teun Klapwijk 51 August 29 - September 9 Baryogenesis and First Order Phase Transitions in the Early Universe Björn Garbrecht, Tomislav Prokopec 53 September 12 - 16 Creativity: Meaning, Mechanisms, Models Johan Hoorn, Frank Kresin, Arjan Postma 55 September 19 - 23 Challenges in Modelling the Reaction Chemistry of Interstellar Dust Stefan Bromley, Fedor Goumans, Ben Slater 57 September 26 - 30 Dynamics of Complex Fluid-Fluid Interfaces Dick Bedeaux, Peter Fischer, Signe Kjelstrup, Leonard Sagis, Thijs Vlugt 49 October 4 - 7 Quantum to Classical Crossover in Mechanical Systems Dirk Bouwmeester, Yaroslav Blanter, Herre van der Zant, Eva Weig Report not available October 10 - 14 TEA-IS: Thunderstorm Effects on the Atmosphere-Ionosphere System Elisabeth Blanc, Ute Ebert, Francisco Gordillo-Vazquez, Torsten Neubert 61

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October 17 - 21 Physics With Industry Marcel Bartels, Marjan Fretz, Floor Paauw, Pieter De Witte 62 October 24 - 28 Error in the Sciences Marcel Boumans, Giora Hon, Arthur Petersen 66 October 31 - November 4 Tipping Points in Complex Flows - Numerical Methods for Bifurcation Analysis of Large-Scale Systems Henk Dijkstra, Fred Wubs 68 November 7 - 11 Uncertainty Analysis in Geophysical Inverse Problems Andreas Fichtner, Peter Jan van Leeuwen, Jeannot Trampert 70 November 14 - 17 Land for Bioenergy: Ecological, Economic and Societal Aspects Ada Ignaciuk, Cornelia Krug, Rik Leemans, Jasper van Vliet 72 November 21 - 25 Towards a Consensus Model of Yeast Glycolysis Matthias Heinemann, Jörg Stelling, Bas Teusink 74 November 28 - December 2 Mathematics: Algorithms and Proofs Thierry Coquand, Henri Lombardi, Marie-Francoise Roy, Bas Spitters 76 December 5 - 9 Isotopes in Astrochemistry: An Interstellar Heritage for Solar System Materials? Conel Alexander, Steven Charnley, Ewine van Dishoeck, Stefanie Milam 77 December 12 - 16 Modeling and Observing Dense Stellar Systems Arjen van Elteren, Piet Hut, Steve McMillan, Inti Pelupessy, Simon Portegies Zwart, Marco Spaans 78 December 19 - 23 MAO - Multi-Agent Organisation Mehdi Dastani, Guido Governatori, John-Jules Meyer, Leendert Van der Torre 80 Funding sources of the Lorentz Center 83

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Preface by the Director The year 2011 has been an extremely busy year at the Lorentz Center. The entire Lorentz Center team has put an enormous energy in setting the wheels in motion for shaping the future of the Lorentz Center. The outcome of all this will only become visible in 2012, but in 2011 the foundations have been laid. Of course, I especially refer to the planned opening of the second Lorentz Center venue in 2012. The new ‘Lorentz Workshops@Snellius’ will be organized in the Snellius building of the Faculty of Sciences of Leiden University, across the street from our ‘classical’ now renamed into ‘Lorentz Center@Oort’ venue. In 2011, all plans about the extension of the Lorentz Center – that have been developing since 2007 (!) – have reached their definite form. Agreements have been finalized with our future co-inhabitants of the Snellius building: the Mathematical Institute (MI), the Leiden Institute for Advanced Computer Science (LIACS) and the central ICT group (ISSC) of Leiden University. The Lorentz Center is currently rebuilding the present library of the Snellius building. A bit more than one half of its total area will become the new Lorentz Center@Snellius venue, the other half will ‘return’ as the completely restyled and upgraded library of the Mathematical Institute. The Lorentz Center has been the driving force behind designing the combined workshop center-library – of course in close consultation with both the Mathematical Institute and the central Leiden University Libraries (UBL). By the end of 2012, we will be able to run two types of workshops in parallel: the classical Lorentz Workshops@Oort with up to 55 participants and the new Lorentz Workshops@Snellius for groups of maximally 25 closely collaborating scientists. We expect the outcome of all this to be exciting: 2012 will be the reap year of all the hard work done in 2011.

Figure 1: The number of workshops and number of workshop participants per year A similar thing can be said about the very successful collaboration between the Lorentz Center and the NIAS (Netherlands Institute for Advanced Study in the Humanities and Social Sciences). This collaboration was initiated in 2006: 2011 was the year in which the Lorentz Center and the NIAS together applied for a renewal of the support by the Royal Netherlands Academy of Arts and Sciences (KNAW). The plan for a renewed collaboration – written together with Aafke Hulk, rector of NIAS – has been received favorably by the KNAW. Subsequently an evaluation of the collaboration and its future plans has taken place in

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December 2011 – by a committee headed by Rob Reneman, a former president of the KNAW. So again, all the hard work has been done in 2011, its product – a stimulating renewal of the KNAW support for the NIAS-Lorentz Collaboration – could only be ‘reaped’ in early 2012. And there is more reaping to be done: a new dimension has been added to the collaboration in the 2011 plans: the Lorentz Center and NIAS are planning to organize ‘theme groups’. These will be groups of 3-5 scientists with varying backgrounds that team up for approximately 3 months at NIAS to work intensely on an interdisciplinary subject and to organize a workshop at the Lorentz Center. We – NIAS and the Lorentz Center – have high expectations of the impact such theme groups may have in the still wide open scientific divide between the exact sciences on one side and the humanities together with the social sciences on the other.

Figure 3: The number of workshop participants by nationality One significant change did take place in 2011. The Lorentz Center has changed its submission procedure from `first come, first serve’ to a format that enables an open competition between proposals. Historically, a workshop week was ‘claimed’ by scientists that planned to organize a workshop – even before a proposal was submitted. This procedure worked very well when the Lorentz Center had plenty of open spaces in the program, but had become too rigid in the last years, in which there were more ideas for interesting workshops than weeks in a year. In the new system, preferred weeks are indicated in the workshop proposal; based on the advice of the Scientific Advisory Boards, workshop weeks are assigned after (the first round of) the evaluation procedure. With this – in a sense more mature – evaluation procedure, the Lorentz Center has set a next step in its evolution as workshop center. While making plans and having discussions with architects, constructors and librarians – among many other people – the Lorentz Center of course never lost its focus on its core business: organizing exciting workshops. On April 8, 1911, Heike Kamerlingh Onnes discovered the phenomenon of superconductivity in his cryogenic lab in Leiden. In the week of April 4-8, 2011, the Lorentz Center workshop ‘100th Anniversary of Superconductivity: Hot Topics and Future Directions’ celebrated this fact, but at the same time sketched and discussed the future evolution of the research field. The credo of the Lorentz Center is that interdisciplinary growth must be built on strength in the fundamental disciplines. A perfect example of this is the workshop ‘Quantitative Methods in Financial and Insurance Mathematics’ that was focused on the financial and actuarial challenges associated to pricing and hedging products, and at the same time was strongly rooted in mathematical analysis.

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The Lorentz Center further extended its expertise at the intersection of science and industry with the workshop ‘Circulating Tumor Cell Isolation and Diagnostics’, that brought together a very diverse group of participants: biologists, physicists, chemists, engineers, medical specialists (oncologists, pathologists) and representatives from pharmaceutical and in-vitro-diagnostics companies. The Lorentz Center naturally considers itself a specialist in organizing workshops, nevertheless, we have ourselves learned new possible stimulating formats for bringing people together through the NIAS-Lorentz workshop ‘Creativity: Meaning, Mechanisms, Models’ organized by the Lorentz fellow Johan Hoorn. This indeed was a very inspiring workshop, both through its scientific theme as well as through the unique set-up of the meeting.

Figure 2: Relative rates of the background of workshop participants in the year 2011 The future of the Lorentz Center – both on the short and on the long run – is looking bright. Much work still needs to be done to prepare the Lorentz Center for the novel developments and challenges this future will bring. Given the shape the Lorentz Center and its team is in, there is no doubt that the Lorentz Center will be able to meet those challenges and to set its own course within the extremely volatile scientific world of the present times.

Arjen Doelman Director Lorentz Center April 2012

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Mission Statement The Lorentz Center coordinates and hosts international workshops in the sciences, based on the philosophy that science thrives on interaction between creative researchers. Lorentz Center workshops focus on new collaborations and interactions between scientists from different countries and fields, and with varying seniority. The Lorentz Center concept In order to allow both junior and senior researchers to catch up with the rapid international developments and to establish new contacts and collaborations, Lorentz Center workshops bring together groups of up to 55 junior and senior researchers in a stimulating environment and with working space for all participants: offices with a desk, white boards and meeting rooms. Through a combination of informal talks, working sessions and discussions, participants are able to assess the status of a field and its future, and to collaborate, establish new international contacts, and spot upcoming talent. Workshops can be proposed and organised by any researcher from any country. Workshops organised by researchers from different scientific backgrounds and nationalities are encouraged. Submission procedures are aimed at rapid evaluation. Proposals for workshops are reviewed by external scientific advisory boards. Currently there are boards for astronomy, computational sciences, informatics, life sciences, mathematics, physics and NIAS-Lorentz workshops. The Lorentz Center program is also open to proposals within other fields of the natural sciences. Collaboration with NIAS In collaboration with the social sciences and humanities institute NIAS (located in Wassenaar), the Lorentz Center welcomes proposals for workshops that bring together one or more disciplines of the natural sciences with those of the social sciences and humanities. Proposals for these workshops are reviewed by the NIAS-Lorentz Scientific Advisory Board. Lorentz Fellowships at NIAS are awarded to scientists who are engaged in research across the boundaries of the humanities and the social sciences on one hand and the natural sciences on the other hand. As part of the fellowship, the Lorentz Fellow is offered the opportunity to organize a workshop at the Lorentz Center. Surrounded by excellence The Lorentz Center is located in Leiden University's J.H. Oort Building which also hosts the Instituut Lorentz for theoretical physics, the Kamerlingh Onnes Laboratory and the Leiden Observatory. The Mathematics, Biology and Chemistry Departments and the Leiden Institute of Advanced Computer Science are located in adjacent buildings. All Dutch universities and research institutes can easily be reached by public transport; the universities in Amsterdam, Utrecht, Delft and Rotterdam can be reached by train within an hour. Schiphol International Airport is only 15 minutes by train. Funding The Lorentz Center is supported by the Faculty of Science of Leiden University, the Dutch Ministry of Education, Culture and Science (OCW), the Dutch Foundation for Fundamental Research on Matter (FOM), and various Research Councils of the Dutch Science Foundation (NWO) and the Netherlands Academy of Sciences.

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Scientific Advisory Boards during the year 2011 Astronomy Board

Chair C. Aerts Katholieke Universiteit Leuven

Members N.J. Evans University of Austin, Texas M. Kessler ESA B. Leibundgut ESO Garching bei München S. Markoff Instituut Anton Pannekoek, Amsterdam R. Morganti ASTRON Dwingeloo J. Schaye Universiteit Leiden R. van de Weijgaert Rijksuniversiteit Groningen Computational Science Board

Chair D. Frenkel Cambridge University

Members F.M. Bickelhaupt Vrije Universiteit Amsterdam H. Bijl Technische Universiteit Delft A. van den Bosch Universiteit van Tilburg H.J.H. Clercx Technische Universiteit Eindhoven M. Dijkstra Universiteit Utrecht H.A. Dijkstra Universiteit Utrecht U.M. Ebert CWI Amsterdam & Technische Universiteit Eindhoven J.E. Frank CWI Amsterdam P.A.J. Hilbers Technische Universiteit Eindhoven R.C. Jansen Groningen Bioinformatics Centre J.N. Kok Universiteit Leiden M. Koper Universiteit Leiden B. Koren Universiteit Leiden K. Mandemakers International Institute of Social History J.M.J. Murre Universiteit van Amsterdam S. Portegies Zwart Universiteit Leiden P.M.A. Sloot Universiteit van Amsterdam J. Trampert Universiteit Utrecht J.J.W. van der Vegt Universiteit Twente L. Visscher Vrije Universiteit Amsterdam J. de Vlieg Netherlands eScience Center P.R. ten Wolde AMOLF

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Mathematics Board

Chair A.W. van der Vaart Vrije Universiteit Amsterdam

Members K. Aardal Technische Universiteit Delft O. Diekmann Universiteit Utrecht G. van der Geer Universiteit van Amsterdam M. Gehrke Radboud Universiteit Nijmegen S.A. van Gils Universiteit Twente R.W. van der Hofstad Technische Universiteit Eindhoven B. Koren Universiteit Leiden N.P. Landsman Radboud Universiteit Nijmegen B. de Pagter Technische Universiteit Delft J.M.A. Scherpen Rijksuniversiteit Groningen J.M. Schumacher Universiteit van Tilburg B. de Smit Universiteit Leiden Informatics Board

Chair M. van Steen Vrije Universiteit Amsterdam

Members M. de Berg Technische Universiteit Eindhoven L. Hardman CWI Amsterdam P.H. Hartel Universiteit Twente C.M. Jonker Technische Universiteit Delft J.N. Kok Universiteit Leiden P. Lucas Radboud Universiteit Nijmegen J.A. La Poutré CWI Amsterdam J. Roerdink Rijks Universiteit Groningen H.J. Sips Technische Universiteit Delft L. Stougie Vrije Universiteit Amsterdam & CWI Amsterdam R. Veltkamp Universiteit Utrecht Life Sciences Board

Chair R. van Driel Universiteit van Amsterdam

Members J.P. Abrahams Universiteit Leiden J.M. Aerts Universiteit van Amsterdam B.M.T. Burgering Universiteit Utrecht N. van Dam Radboud Universiteit Nijmegen J.J. Heijnen Technische Universiteit Delft R. Kanaar Erasmus MC M. Merrow Rijksuniversiteit Groningen M. Verhage Vrije Universiteit Amsterdam

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Physics Board

Chair J. Knoester Rijksuniversiteit Groningen

Members A. Achúcarro Universiteit Leiden H.J.H. Clercx Technische Universiteit Eindhoven N. Dekker Technische Universiteit Delft M. Dijkstra Universiteit Utrecht A.J.H. Donné FOM Instituut voor Plasmafysica Rijnhuizen U. Ebert CWI & Technische Universiteit Eindhoven J.F.W.M. Frenken Universiteit Leiden M.S. Golden Universiteit van Amsterdam M.I. Katsnelson Radboud Universiteit Nijmegen R. Loll Universiteit Utrecht P.H.M. van Loosdrecht Rijksuniversiteit Groningen M.A.J. Michels Technische Universiteit Eindhoven F. Mugele Technische Universiteit Twente V. Subramaniam Universiteit Twente E. Verlinde Universiteit van Amsterdam P.R. ten Wolde AMOLF NIAS-Lorentz Board Chair A.H.G. Rinnooy Kan Sociaal Economische Raad

Members E. Aarts Philips K. van Berkel Rijksuniversiteit Groningen R. Bod Universiteit van Amsterdam D. van Delft Museum Boerhaave & Universiteit Leiden R. H. Dijkgraaf KNAW J. W. McAllister Universiteit Leiden R. van der Ploeg European University Institute San Domenico di Fiesole P. Tindemans Euroscience Den Haag L.C. Verbrugge Rijksuniversiteit Groningen

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Landing Sites for Exploration Missions

January 17 – 21, 2010 The first European Workshop on Landing Sites for Exploration Missions took place at the Lorentz Centre, in Leiden (NL) on 17-21 January 2011. The workshop was organised in the framework of a Europlanet JRA1 (Support to Future Missions) grant. It gathered more than sixty participants from the space science and engineering communities in Europe, the Unites States, and Asia. The workshops program combined a series of lectures presenting different perspectives on landing sites, with hands-on sessions involving small, interdisciplinary teams focusing on specific mission scenarios. The goal of the workshop was to bring together the international landing site community to start preparing for landing site selection and characterization activities serving missions having a European component. The week was concluded with a conference at ESTEC, focusing on the international programmatic context of robotic exploration missions. After the workshop the participants released a number of recommendations. 1. Maintain and further develop a coordinated forum through which scientists and

engineers can interact and communicate on the topics of future exploration missions (design, landing sites, operational aspects). Face-to-face workshops are essential in this process, as well as a continuum of information exchange and discussion via a web-based platform such as PlanetaryGIS.org. This will facilitate the convergence of the currently fragmented knowledge and expertise present in the European planetary community, and will serve as a platform to coordinate international efforts in this field.

2. Landing site selection activities for the Mars 2018 mission need to be commenced as soon as possible, because currently active orbiter missions (MRO, Mars Express) providing critical landing site data are already in their extended missions and may have a limited remaining lifetime. There are no follow-up missions planned with the complement of instruments currently available on MRO and Mars Express.

3. Precision landing and hazard avoidance are critical technologies, which have the potential to greatly enhance the science and exploration return of missions. These technologies provide the opportunity to land in terrains with high science and exploration interest that would otherwise be inaccessible.

4. All landing site selection processes in the framework of ESA-NASA cooperative programs be conducted in a joint manner.

5. Implement a funded European data analysis and dissemination program to exploit ESA mission data in preparation for Mars, Lunar, and small bodies missions. Both long-term strategic and shorter-term mission dependent activities should be covered: a) strategic activities include planetary cartography, geological mapping, mapping standardization; b) a data utilization program to allow scientists to do the preparatory research before proposals for landing sites can be developed in support of ESA missions; c) analysis of data for which the knowledge resides in the science community (e.g. atmospheric models, digital terrain models) is recommended to be managed in a project independent, open, and competitive manner.

The participants thank Europlanet, The Lorentz Centre, the ESA Directorate of Science and Robotic Exploration and the Directorate of Human Space Flight, DLR, CNES, ASI, colleagues from NASA, JPL and JAXA, and participants from industry (Thales Alenia Space – Italy) for their contribution to this inspiring workshop. The presentations given at the workshop and

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subsequent conference can be downloaded from: http://www.planetarygis.org/wiki/Workshop2011/Program. Agustin Chicarro (Noordwijk, the Netherlands) Roderik Koenders (Delft, the Netherlands) Tanja Zegers (Utrecht, the Netherlands)

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Physics of Mixing

January 24 – 28, 2011 Scope and challenges Mixing of scalars (e.g. chemical species or heat) by laminar and deterministic flows is key to many industrial and natural fluid systems of size extending from microns to hundreds of kilometers. Examples are diverse and include mixing of viscous fluids, compact processing equipment and a rapidly expanding range of micro-fluidic applications as well as magma transport in the Earth’s mantle, gas exchange in lung alveoli and distribution of blood-borne pathogens. Profound fundamental insight into mixing has great relevance and is imperative for further technological development of, especially, micro-fluidics applications and process engineering. Key challenges are: 3D realistic fluid systems; experimental mixing studies; (further) mathematical and conceptual development of 3D transport formalisms; their translation and integration into analysis and design strategies; (further) development of numerical and experimental methods for transport studies. Aim and format The workshop sought to address the above challenges by providing a platform for physicists, mathematicians and engineers for exchanging their ideas and views on mixing and promote cross-disciplinary collaboration. To this end a program of keynote lectures by leading experts and (invited) contributed talks by senior and junior scientists was compiled around the following themes: Theme 1: Mathematical concepts for mixing and chaotic advection. Theme 2: Mixing and chaotic advection in viscous flows and microfluidics. Theme 3: Mixing and chaotic advection in environmental and natural systems. The workshop and beyond The participants represented a good cross-section of the mixing community, ranging from leading experts to junior scientists. The workshop was well received and considered a timely event. Attendance at presentations was high and interaction and active contribution was strong. Moreover, participants were highly appreciative of the excellent facilities and organization of the Lorentz Center. In conclusion, we feel that the workshop was successful and achieved its aims. The status of mixing research and future directions were wrapped up in a closing lecture. Moreover, methods and concepts in mixing studies will be reviewed in a special issue in Advances in Applied Mechanics (aimed at non-experts and students) and a state-of-the-art article in Reviews of Modern Physics (aimed at experts). This is currently in progress and includes contributions primarily by workshop participants. Finally, first plans for a follow-up meeting in 2-3 years from now were made. Acknowledgment The organizers wish to express their sincere gratitude to the Lorentz Center for facilitating and co-organizing the workshop. They furthermore acknowledge additional financial support by FOM, the JM Burgers Centre and TU/e. Julyan Cartwright (Granada, Spain) Herman Clercx (Eindhoven, the Netherlands)

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Gert-Jan van Heijst (Eindhoven, the Netherlands) Michel Speetjens (Eindhoven, the Netherlands)

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New Biology and Society: Opportunities, Challenges and Myths

January 31 – February 3, 2011

Scientific motivation and structure of the workshop The question underlying this workshop is how our society should deal with the benefits and challenges posed by the profound, powerful and potentially disruptive knowledge in biology. Issues were classified in three domains: (i) managing the new life sciences, (ii) societal reception and expectations, and (iii) normative issues. These three issues structured the program in that on Monday the workshop concentrated on fundamental changes in the life sciences, Tuesday on what is required for a fruitful debate with the general public, while on Wednesday we dealt with normative questions. Thursday was devoted to wrap-up and make first steps towards a publication on the outcome of the workshop. The morning sessions were plenary; two presentations introduced the issue addressed that day. The afternoon was filled with breakout sessions followed by plenary discussions. Participants The workshop was attended by 30 persons: 13 biologists, 5 philosophers, 7 sociologists, and 5 of other disciplines. Roughly 20% were in the category ‘young scientists’. One MSc student of the Leiden University honors program participated. Breakout sessions The breakout sessions constituted the heart of the workshop. Breakout groups always were a mixture of disciplines. In the afternoon four groups were assigned each with a different but complementary set of issues to address during an about 2 hours session. This was followed by a short plenary presentation of conclusions of each group (one slide with bullet points each) followed by extensive plenary discussions. Results of the workshop The workshop intended to bring together different disciplines from the life sciences and the humanities to explore how to deal with the rapidly increasing biological knowledge that is drastically changing our life. We can profit from this only if our society supports and embraces new ideas and potentials that result from research in the life sciences domain. Obviously, this workshop did not provide definitive answers to these and related questions. However, it did analyze and structure the problem by defining the issues and searching for parallels in other sciences and in the recent past. The unusual mix of disciplines made this an exciting and remarkably fruitful endeavor. Results are presently summarized in a manuscript that will be submitted to a general widely read international journal (e.g. Nature). In addition, one or two papers may be written for a more specialized audience. Social aspects The atmosphere at the workshop was open and pleasant, sparking off ample informal discussions in addition to the formal workshop sessions. Dinner at the NIAS in Wassenaar was well-appreciated by the participants. Lorentz Center The organizers want to express their gratitude to the Lorentz Center for their experience, facilities and financial support that were essential for this workshop. In particular the Lorentz

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Center staff is thanked for their smooth organization and support before and during the workshop. Johan Braeckman (Gent, Belgium) Roel van Driel (Amsterdam, the Netherlands) Tsjalling Swierstra (Maastricht, the Netherlands)

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Circulating Tumor Cell Isolation and Diagnostics: Towards Routine Clinical Use

February 7 – 11, 2011

Aim Circulating tumor cells (CTCs) are released from primary and metastatic tumors into the blood and have high clinical diagnostic potential in oncology, especially within the context of personalized treatment of patients with metastasized cancer. Obtaining CTCs from blood is a challenge. The aim of this workshop was to create a high level of multidisciplinary knowledge of the developing CTC field and, based on this, define a plan on how to develop and integrate CTC diagnostics into routine clinical oncology practice to improve quality of patient care, including partnerships, collaborations and research proposals. The outcome of the workshop A consensus on the definition of a CTC appeared to be difficult to obtain, in view of the heterogeneity of CTCs. It became clear that the heterogeneity was greater than so far expected, and that cancer stem cells, possibly with their progeny cells, might largely be accountable for this. All agreed that, in addition to the currently available “golden standard” CellSearch CTC counting assay to predict prognosis of the patient and monitor the effect of therapy, these rare cells are required to develop companion diagnostic assays to predict response to a certain drug. Both pathology stainings for protein, RNA and DNA biomarkers were considered relevant, as well as DNA and RNA sequencing. The technical sessions revealed that there are many potential technologies to isolate CTCs, and that specific approaches might be especially suited to detect CTCs of a specific tumor type, for example a filter approach to isolate the large CTCs from Non Small Cell Lung Cancer. During the final discussion it was decided to write a meeting report and to try to obtain funding to establish a working committee on standardization of CTC isolation approaches, which is a crucial step on the road towards rapid clinical implementation of CTC diagnostics. The created bond between the participants is probably the best guarantee for actual execution of the plans made and for continuation of the dialogue on CTC diagnostics. A potential breakthrough A number of the participants had noticed during their research a similar phenomenom, that is a remarkable heterogeneity among CTCs of the same patient, that was considered a potential artifact, or at least unexplained, and therefore in general not mentioned. During the workshop it became clear that this was a more general phenomenon than thought, and probably not at all an artifact. During the discussions the hypothesis arose that CTC heterogeneity within one patient might be caused by stem cell-like CTCs, differentiating along the hematopoietic lineage while circulating in the blood. Without doubt this line of thought will be pursued in the coming years, and if proven true, will present a very important scientific breakthrough in the field. Format and structure of the program The very friendly and inviting atmosphere of the Lorentz Center, the cozy common room, including free drinks, each participant his or her own “Lorentz mug” to drink from, a very Dutch boat tour, and the mixture of lectures and discussion time created a very stimulating

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and pleasant setting, where participants really felt at home, and were willing to very openly share their results, including those they had doubts about. Despite the absence of any formal confidentiality agreement, this appeared to be the case for both academic and commercial participants, and resulted in unique discussions, friendships and multiple future scientific collaborations. The world known breast cancer expert Larry Norton even decided to miss his plane, in order to not miss the final half hour of the Friday discussion… The mixture of commercial participants -from pharma, IVD and technology companies-, a wide range of academic participants from the engineering, cell and molecular diagnostics areas, and medical specialists enabled unique interactions and exchange of experience and expertise, and definitely contributed to the success of the workshop. Klaus Pantel (Hamburg, Germany) Stefan Sleijfer (Rotterdam, the Netherlands) Anja van de Stolpe (Eindhoven, the Netherlands) Leon Terstappen (Enschede, the Netherlands) Jaap den Toonder (Eindhoven, the Netherlands)

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Multiscale Fluid Dynamics with the Lattice Boltzmann Method

February 14 – 18, 2011

The Lattice Boltzmann method is a relatively new computational methodology but already widespread and well established. During the last years it has demonstrated numerous advantages with respect to other computational methods. These include not only highly efficient parallelization and implementation techniques, but also advanced models bridging the physics between microscopic systems and macroscopic applications. The scope of the present workshop was to bring together scientists who are currently using the Lattice Boltzmann technique to study computationally challenging problems in different application areas. Our expectation was to obtain a clear picture of where the methods have been pushed so far, which validations have been performed, which techniques and knowhow could be transferred between different application areas / communities. These aims and expectations have been achieved by up to 53 participants from different scientific fields who participated in the workshop and discussed the various aspects of the method. Very positive feedback has been obtained from various participants on the scientific gain of the workshop. The workshop covered five days and four themes: “Flow at the microscales'', “Turbulent and multiphase flows'', “Biological fluid dynamics and soft condensed matter'', and “Model development''. The Lorentz Center facilities really helped in creating a friendly and interactive atmosphere amongst participants. The scientific level of the presentation was very high and focused on the state-of‐ the‐ art in respect to where the method has been pushed for different scientific problems. The combination of key-experts and young scientist helped in creating a very interactive atmosphere. During the workshop there has been a session on the scientific activities of the Dutch community working with the Lattice Boltzmann method. This session has been organized in the context of the activities of the JM Burgerscentrum contact group on Lattice Boltzmann techniques (www.jmburgerscentrum.nl). A round table was organized to discuss the Lattice Boltzmann in relation to Engineering Applications, while a day was reserved to discuss Lattice Boltzmann in relation to industrial problems. Multiphase and multicomponent flows are indeed ubiquitous in industry and the Lattice Boltzmann is a tool which offers large possibilities in terms of physical modeling, with relative ease of implementation and adaption to complex flow geometries. The industry day has been co-organized by Ramin Badie (ASML, Veldhoven, The Netherlands), Xiaowen Shan (EXA Corporation, Boston, USA), Herman Wijshoff (Océ, Venlo, The Netherlands). Xiaowen Shan presented the experience of EXA Corporation and its commercial solutions. Ramin Badie and Herman Wijshoff presented a list of scientific problems involving fluids where the Lattice Boltzmann method could have good advantages with respect to other flow solvers. This session was well received and many scientists reacted with immediate feedback. Another point that was addressed is the possibility to develop a community Lattice Boltzmann code. Our vision is that the Lattice Boltzmann method is now in its maturity and

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has all the capabilities to provide a community code which can incorporate fluid dynamics and different physics at disparate scales. A round table was organized to discuss about this possibility. All participants considered the idea relevant and we had rather extensive discussions on what could be the best technical choice to make first steps in this direction. Former attempts were discussed critically and the community decided to: 1) immediately start a virtual meeting point where experts can exchange information as well as data, code examples, etc; 2) circulate a document with the minutes of the discussion on the community code and a form to be filled by different groups to better characterize their requirement, expectations and current codes. We would like to thank on behalf of all participants the staff of Lorentz Center for their efficient help and support which made this workshop possible. We also thank the sponsors which contributed to the success of this initiative. Herman Clercx (Eindhoven, the Netherlands) Jens Harting (Eindhoven, the Netherlands) Sauro Succi (Rome, Italy) Federico Toschi (Eindhoven, the Netherlands)

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Probing the Radio Continuum Universe with SKA Pathfinders

February 21 – 25, 2011

Background Several next-generation "SKA pathfinder" radio telescopes and upgrades are under construction around the world, each planning major radio continuum surveys. This workshop was held to bring together expertise in both science and survey techniques, to coordinate developments, to avoid duplication of effort, and to ensure that each project has access to best practice. The workshop included discussion of specific science goals, to ensure cross-fertilisation of ideas and optimum survey strategies. The workshop differed from a conference in emphasising the importance of discussions as well as formal presentations, and therefore consisted of four components: 1. Review presentations to set the scene for the detailed discussions 2. Contributed presentations, including both oral and poster presentations 3. Organised discussions on particular topics 4. Ample time for informal discussion and preparation Specific Outcomes The primary outcome was to rethink some aspects of the way we are constructing these telescopes and designing the surveys. Other outcomes were to resolve that (a) such a meeting is invaluable in bringing the experts together from the various projects to share expertise and prevent duplication of effort, (b) we should hold a similar meeting one year from now, (c) we should also facilitate smaller meetings for specialist groups to share expertise between the projects. The meeting voted not to produce a conventional "Proceedings" but instead will produce a paper in a refereed journal with short contributions from all the speakers, who will be co-authors. We don’t yet know whether this is successful, but it's an interesting experiment! There were several "aha" moments: The cosmologist had been invited to tell us, specifically, what these surveys will do in

testing cosmology. In preparation for the meeting, the cosmologists did their homework and came up with some surprising results: the impact of these surveys on cosmology and fundamental physics may even dwarf the science goals we have been working on for the last few years.

Jim Condon pointed out some hitherto-unrecognized constraints which may mean we have to change our survey strategy, and perhaps redesign our calibration processes.

Overall Evaluation and Feedback The workshop was extremely successful. Lively discussions took place during every break and many impromptu meetings were held to address specific issues. I don't know how you guys do it, but somehow you manage to create an environment which engenders productive discussion. The offices, the whiteboards, the relaxing lounge room with excellent coffee, and the wine and cheese, all create an atmosphere in which people feel comfortable discussing critical issues. We requested wine be served at the end of each of the two days on which there were no other scheduled events, and this worked really well. Relaxing over a glass of wine after a day of focussed talks tends to bring out other solutions. People invite each other to their home

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institutions, or discuss how they might work together to address a problem. I strongly recommend this for future meetings. All the facilities were excellent, everything worked well, and all the staff (particularly Pauline Vincenten) were incredibly helpful. The funding for participants was invaluable in bringing some who might otherwise have not attended. Two suggestions for improvement are: Spare radio microphones for use when recording discussions (our hand-held microphone

failed during the meeting). It would be nice if the lecture room were closer to the other rooms of the Lorentz center! Many thanks for a great meeting! Ray Norris (Epping, Australia) Huub Röttgering (Leiden, the Netherlands)

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Herschel and the Characteristics of Dust in Galaxies

February 28 – March 4, 2011 The Herschel Space Observatory and previous infrared space missions (ISO, Spitzer) have provided us with very detailed Spectral Energy distributions for many (classes of) galaxies. The goal of the workshop was to overview the state of the art in studies of the characteristics of dust and their influence on the spectral energy distribution of galaxies. It brought together astronomers involved in observations of dust in galaxies, astronomers versed in the modelling of spectral energy distributions, theoreticians with deep understanding of the physical and chemical processes affecting dust in space, experimentalist studying the characteristics of materials of astrophysical relevance in the laboratory, and astronomers studying galaxies at high redshifts. The workshop was extremely successful, as measured by the extremely lively daily debates, and by the reaction of several participants afterwards. One of the reasons for this was its very timely nature. On the one hand there is a wealth of new and unique data, especially from the Herschel and Planck space observatories (the latter just released), on the other hand there are significant new insights provided by recent theoretical work and ground-based laboratory measurements. Much of this occurs in distinctly different communities that often have, at best, weak communicative ties between them. The workshop provided this missing communications link, leading to frequent eye-openers and identification of unjustified prejudices. In particular the laboratory results on submillimeter dust emissivity were found to effectively rule out all simple dust-mass estimates, to the surprise (and dismay) of many attendants. A tangible outcome was the decision to collect post-workshop a number of characteristic observed SEDs and have the various modelling groups use their codes to extract essentially the same (dust) information from these SEDs, thus providing a very valuable benchmarking exercise. This is now in progress. The format of the workshop: review-type presentations on topics covering most of the field, grouped together, and followed by very extended (plenary) discussion sections worked quite well. The participants stayed till the very end and, more importantly, took part in the discussions until the last moment. There is only one point of criticism. The location of the lecture room in the Huygens Laboratory is very close to the elevator hall on the second floor. In this hall, tables and chairs invite students to gather between lectures, and converse loudly. Too loudly, as it turns out. Loud voices and other student noise was a frequent source of distraction, and even irritation during the week. Frank Israel (Leiden, the Netherlands) Xander Tielens (Leiden, the Netherlands)

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Modeling Natural and Artificial Phytosynthesis

March 7 – 11, 2011 Description and Aims A detailed understanding of how natural photosynthesis works can guide the development of photochemical devices for the capture and conversion of solar energy into fuels. In this workshop scientists working on phenomenological theories together with scientists working on first-principles microscopic approaches joined their expertise to build a common strategy for modeling and designing artificial photosynthesis devices. Key topics covered in the workshop included light harvesting complexes and exciton dynamics, photo-induced charge separation, multi-electron catalysis, proton-coupled electron transfer, and design of artificial photosynthesis devices. Tangible outcome The workshop provided a unique opportunity for the groups actively working in this field to share their recent progress and to discuss possible strategies to describe the multiscale light-driven processes in photosynthesis. During the workshop animated discussions followed the talks in which results of microscopic and phenomenological models were presented. A particularly hot topic was the use of the detailed output from quantum-chemical calculations to the phenomenological models used in describing light harvesting and exciton dynamics. Another highlight was the discussion about the structure and mechanism of the oxygen-evolving complex of photosystem II in which we were happy to have two key players in the field among the participants (Siegbahn and Batista). The workshop was connected with the Leiden University Honours Programme 2010-2011 and the class “Modeling Natural and Artificial Photosynthesis”. Bachelor students have attended the workshop as young participants after preparation with an introductory course. Some of them have performed their Bachelor research internship in the field covered by the workshop. Organization/Format The program was organized to give ample time to discussions and many spontaneous discussions were indeed initiated and continued in the coffee room. Many young scientists used the opportunity to present their research in the form of a poster and benefited from the attention of the senior participants to discuss their work. These poster sessions constituted another important occasion for informal and fruitful discussions. The participants clearly enjoyed the workshop both for the scientific aspects as well as for the excellent facilities provided by the Lorentz Center. The support of the staff of the Lorentz Center, especially of Corrie Kuster, Henriette Jensenius and Mieke Schutte, in preparing and organizing the workshop is gratefully acknowledged. This workshop would not have been possible without the financial support of the Lorentz Center, the BioSolar Cells program, and the Leiden University Honours Program. Francesco Buda (Leiden, the Netherlands) Markus Reiher (Zurich, Switzerland) Lucas Visscher (Amsterdam, the Netherlands)

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Cosmic Ray Interactions: Bridging High and Low Energy Astrophysics

March 14 – 18, 2011

Cosmic rays are an energetically important ingredient of the interstellar medium (ISM), but until recently it was difficult to map the cosmic ray content of the Galaxy. With the coming of age of GeV/TeV gamma-ray astronomy this situation has dramatically changed, because the radiative effects of cosmic rays can be imaged directly with arcminute resolution. At the same time there is a wealth of information from radio, submm, and infrared wavebands on the magnetic field configuration, and the distribution and abundance of dense matter in the Galaxy with which cosmic rays interact. This provides vital information for the researchers working on GeV/TeV observations, in understanding the targets for accelerated particles. In parallel, researchers working in low energy astrophysics need information about the low-energy end of the cosmic ray distribution because it provides an important, perhaps sometimes even the only, source of ionization in dense, cold, molecular clouds. Thus even though the low and high energy cosmic rays are separated by decades in energy, by using both gamma-ray and molecular cloud chemistry as tracers, a new lever arm for understanding source physics and cosmic ray acceleration can be exploited. At the same time, understanding the complications of UV versus X-ray versus cosmic ray ionization is a burgeoning new field. During this workshop all the above mentioned aspects were discussed. Both the organizers and the participants were very satisfied with the workshop, as there are otherwise few occasions where such different scientific communities interact. The format of the workshop consisted of many long talks intended to bring both communities up to date, and some contributed talks on recent, interesting results. At the last day four groups, two from each community, presented their ideas of what they think researchers from the other community could investigate. During the week time was reserved for the groups to work on these final talks. There was some confusion concerning this idea, as participants were not quite sure how detailed their proposals for research should be, but in the end participants were pleased by what this format had accomplished, namely lively discussions during the group sessions, on what they had just learned from fields that were new to them. During the workshop the high energy astrophysicists became much more aware of the molecular tracers of cosmic rays interactions, with H3+ being one of the most important molecules. They also became aware of the importance of low energy cosmic rays (up to 10 MeV). These cosmic rays are usually ignored by cosmic ray scientists because they are difficult to detect, due to interference caused, e.g. by solar modulations, although future MeV gamma-ray satellite missions could fill that gap. The low energy astrophysicists were brought up to date on the recent developments in GeV and TeV astronomy, and learned how these fields have revealed the presence of cool regions in the ISM that escaped the attention of radio, submm and infrared astronomy. Participants also became more aware of the potential diagnostic power of Fe-K fluorescent lines around 6.4 keV, which could be induced by interactions between cold gas and MeV protons. These lines were also discussed during the meeting in the context of cosmic ray interactions in the

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Galactic Center region. The 6.4 keV feature is detected from many clouds there, but there is a debate on whether it is induced by a past bright X-ray flare from the central black hole, or whether it is caused by low energy electron or ion cosmic rays. In fact, different cloud complexes within the Galactic Center prefer different ionization mechanisms, respectively. The impression of the organizers, which is supported by comments and e-mails from the participants, is that this was an extremely useful and timely workshop. Both communities learned a lot from each other. The talks were in general very good, and speakers tried to bring across their arguments keeping in mind that they were addressing a diverse community. It was also interesting to see how the different communities have sometimes overlapping jargon with different meanings. An example was the confusion about the term “secondary electrons”, which for low energy astrophysicists means the electrons liberated after ionizations, whereas for a cosmic ray physicists means the electron created after the decay of pions, which themselves are created after high energy proton-proton collisions. Some ideas that came out of this workshop are: the use of H3+ molecules to trace the distribution and origin of low energy cosmic rays; the importance of future MeV satellite telescopes to do the same; the potential use of 6.4 keV line emission to trace low energy cosmic ray interactions. The general feeling at the end of the workshop was that we should stay in touch as an interdisciplinary community, and exchange more information about ideas and potential observing campaigns. To that end we are in the process of setting up a Wiki. All Lorentz Center participants will have access to the Wiki, and already several non participants have asked to be involved. We will post there the presentations and papers from our Lorentz Center workshop website, as well as start new pages for questions and observation organization. There was also a call for trying to do a similar meeting in two years time, so our sense is that we have put something in motion with this workshop that will have lasting effects, perhaps even leading to larger conferences, since the interest level was so high. Sera Markoff (Amsterdam, the Netherlands) Jesus Martin-Pintado (Madrid, Spain) Diego Torres (Barcelona, Spain) Jacco Vink (Utrecht, the Netherlands) Farhad Yusef-Zadeh (Evanston, USA)

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Control of Burning Plasmas

March 21 – 25, 2011 In future fusion devices the power generated by the fusion reactions substantially exceeds the external input power (Pfusion/Pin ≥ 10). When this occurs one speaks of a burning plasma. A new phenomenon in burning plasmas is that the alpha particles, which form a minority but carry 20% of the generated fusion power, can collectively drive certain types of magneto-hydrodynamic (MHD) modes, while they can suppress other MHD modes. Some of these effects on the plasma are desirable, whereas others can be detrimental. The workshop was aimed at making breakthroughs in the field of MHD control in burning plasmas. Specifically, the workshop intended to broaden the area of scientists involved, and seek for inspiration by enabling multi-disciplinary viewpoints and exchange of ideas. A secondary goal of the workshop was to develop a clearer idea of which specific aspects of the control of burning plasmas requires experimental or modelling R&D, and to prioritise these aspects. The workshop was attended by 65 participants from different disciplines (including 32 from The Netherlands and 24 junior scientists). The most difficult hurdle to overcome was the fact that plasma physicists in general have the opinion that to be able to control a plasma you first need superb theoretical models that describe the plasma physics as good as possible. In contrast, control engineers are of the opinion that an as simple as possible model should be used for control, describing only the basic physics of the mode to be controlled without necessity to cover all detailed features. The interaction between physicists, control engineers, and theoreticians was very refreshing and led to several new research ideas to pursue (e.g. simplified transport models provided by plasma theoreticians for being used by control engineers). Additional to the ideas for joint scientific work two cross-disciplinary courses were proposed to be organized in the future: an introduction to control techniques (bachelor level) for plasma physicists, as well as a course into the basics of plasma physics for the control engineering community. Almost all participants signed up for having such courses organized. A total of 15 participants indicated at the end of the workshop that they would be willing to submit a paper to a special issue on Control of Burning Plasmas of the high impact journal Nuclear Fusion. The idea for this is presently being discussed with the Board of Editors of the journal. The format of the workshop was considered to be excellent with significant time devoted to discussions. One of the discussion sessions was organized as a ‘House of Commons’ discussion in which the audience was distributed in two parts with rather opposing views on how to achieve something. This discussion was at the one end very playful, but at the other helped significantly to create a better understanding between the various disciplines. Only positive comments have been received from the participants: on the scientific program and on the format of the workshop with ample time for discussions (...I consider it as a 1 week sabbatical in our stormy area…), on the facilities and the support by the staff of the Lorentz Center as well as on the social events (the wine and cheese party and the Indonesian buffet on a boat trip through the ‘Groene Hart’).

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Tony Donné (Nieuwegein, the Netherlands) Barry Koren (Amsterdam/Leiden, the Netherlands) Jo Lister (Lausanne, Switzerland) Didier Mazon (Cadarache, France) Pieter Nuij (Eindhoven, the Netherlands) Maarten Steinbuch (Eindhoven, the Netherlands)

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Beam shifts – Analogies between Light and Matter Waves

March 28 – April 4, 2011

The law of specular reflection in geometrical optics is among the oldest laws known in physics. It does, however, only hold approximately when a real light beam (described as a spatially confined vector field) impinges on a real material surface. Compared to a specularly reflected reference, the reflected beam can be shifted and deflected in and out of the plane of incidence, with the deviation depending on the angle of incidence, the spin angular momentum (polarization), and the orbital angular momentum of the incident beam. Analogous effects also occur for matter waves, such as neutron beams, and in condensed matter physics, where a prominent example is the Spin Hall effect. The aim of this workshop was to bring together researchers from the relevant communities to explore the interdependence and analogies of the different shift effects. How far do the analogies go, and which novel shift effects can be expected to be discovered in other systems like neutron and electron beams? An intriguing optical beam-shift effect which facilitated this discussion is the “Spin Hall effect of light”, which is a counterpart to the spin Hall effect in condensed-matter physics. Another example is the angular Goos-Hänchen shift, whose analogues for electrons and neutrons had not been considered prior to our workshop. Through a series of outstanding tutorials, lectures, research talks, and lively discussions between the sessions we achieved a significant step towards a unified understanding of these shift effects. There is now a much improved awareness of their commonalities and important differences, which will stimulate further research in a variety of directions. For instance, the spin Hall effect in condensed matter comprises several subtle effects, some of which require the presence of a periodic potential and external fields. In the conventional setting of optical beam shifts these are not present, and it has been intensely discussed between the different communities how periodic photonic nanostructures offer an excellent testbed to study these analogies more closely. Furthermore, there are now plans to search for the angular Goos-Hänchen shift with neutrons. This workshop has served as a potent catalyst for new collaborations, and at least one joint publication is in preparation. The first two days of the programme were deliberately intense, with tutorials and more specialized talks by experienced researchers, and flash talks from the more junior participants. In this way we identified a number of questions, which were then addressed in informal and moderated discussion sessions. The second part of the workshop featured no more than 4 talks per day and therefore left room for more extensive discussions. We also offered guided tours through four laboratories, which proved to be a great success as they connected the more abstract discussion from the talks with concrete experimental realizations. This format was met with great enthusiasm by the participants, which were ideally balanced between senior and junior researchers, as well in regard to representation of the relevant communities. In short, the workshop was a complete success. The participants and scientific organizers wish to express their great appreciation for the work and support of the Lorentz Center. The organizers acknowledge financial support from the following organizations: NWO, Leids

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Universiteits Funds, International Newton Fellowship and the Quantum Optics & Quantum Information Group at Leiden University. Andrea Aiello (Erlangen, Germany) Konstantin Bliokh (Galway, Ireland) Eric Eliel (Leiden, the Netherlands) Jörg Götte (Bristol, United Kingdom) Victor de Haan (Puttershoek, the Netherlands) Wolfgang Löffler (Leiden, the Netherlands) Henning Schomerus (Lancaster, United Kingdom)

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100th Anniversary of Superconductivity

April 4 – 8, 2011 Description and aims 100 years ago superconductivity was discovered by Heike Kamerlingh Onnes in Leiden. Tempted by the unique possibility of an exact match in time and place, the workshop “100th Anniversary of Superconductivity: Hot Topics and Future Directions”, was held from 4–8 April at the Lorentz Center. The mission was not only to mark this centenary but also to capture the current opinion as regards to unconventional superconductivity and to identify future directions. To do this, the workshop brought together a select band of experimentalists and theoreticians for a lively and fascinating exchange of views on experimental data, theories and opinions covering a wide variety of superconducting systems. Scientific outcome The topics covered at the workshop ranged from organic compounds, heavy fermions, iron-based oxides, cuprates, non-centrosymmetric materials and field-effect superconductivity, as well as string theory applied to superconductivity. An obvious challenge is to provide a unifying framework for the understanding of these diverse materials systems. A recurring theme throughout the workshop was that on varying pressure, magnetic field, or some material parameter, a quantum phase transition is often observed between the superconducting phase and a magnetically ordered phase. This connection suggests that quantum phase transitions could play an important role in the mechanism of superconductivity in a number of the relevant materials families. The questions as to which classes of superconductors this applies, and to what extent a revision of BCS theory is needed, were at the centre of discussions at the workshop. One of the refrains of the workshop was the need to understand the ‘normal’ conducting state, of which the superconducting state is an instability. That practically all unconventional superconductors possess anomalous or strange normal states could be linked to the effects of a funnel of quantum critical matter extending above the critical point, as the relevant control parameter is tuned close to optimal Tc, the superconducting transition temperature. However, the nature of the quantum critical order differs from one material to another. For example, in several of the heavy fermion superconductors it is a spin-density wave. In the cuprates, there are a wide variety of suspects, but an increasing number of indications are found that, in addition to charge/spin stripes, anti-ferromagnetism, inhomogeneities and lattice distortions, a time-reversal symmetry breaking order occurs, which leaves translational symmetry intact, with a quantum phase transition to a Fermi liquid close to optimal doping. The potentially central role of quantum criticality in strongly interacting fermionic systems has also inspired novel theoretical approaches, and one session dealt with holographic superconductivity, anti-de Sitter/conformal field theory correspondence and the connection to string theory. A News and Views article reporting the workshop appeared in Nature Physics: D. van der Marel and M.S. Golden: Heike’s Heritage, Nature Physics 7, 377-388 (2011). Format of the workshop The one week program of the workshop consisted of 15 formal presentations and 8 discussion sessions, spread over the first four days. The last day was dedicated to the centenary celebrations themselves, held at the Boerhaave Museum and the former Kamerlingh Onnes Laboratory. All in all, it was a highly stimulating and enjoyable week, with discussions – although sometimes high in volume and passion – always conducted in the

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forgiving manner of an extended family gathering to discuss, disagree and dream at their celebration of a remarkable milestone in physics. The organizers – and participants – are grateful to the Lorentz Center and its staff for the warm hospitality and smooth organization. Mark Golden (Amsterdam, the Netherlands) Dirk van der Marel (Geneva, Switzerland) Kosmas Prassides (Durham, United Kingdom) Anne de Visser (Amsterdam, the Netherlands) Jan Zaanen (Leiden, the Netherlands)

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Advanced Magnetohydrodynamics

April 11 – 15, 2011 This workshop, named after the 2010 Cambridge University Press book by Hans Goedbloed, Rony Keppens and Stefaan Poedts [ISBN 9780521705240 (Paperback) ISBN 9780521879576 (Hardback)], brought together experts from various disciplines sharing an interest in applications of – as well as fundamental theory for – magnetohydrodynamic (MHD) plasma modeling. It was attended by 56 participants, and served as a sequel to the earlier March 2005 workshop on Principle of Magnetohydrodynamics. The keynote speakers brought state-of-the-art views on contemporary plasma physics issues, and both opening and closing keynotes were given by renowned scientists: Prof. Emer. Gene Parker opened up our week of lively discussions with mathematically solid arguments on field line topologies leading to rapid magnetic reconnection. Our closing speaker, Prof. Alan Boozer, gave a similarly enlightening discussion on magnetic island formation from laboratory fusion experience, translating the physical argumentations to what they imply for astrophysical plasmas (and stirring up the discussion on solar coronal heating). Both talks led to vivid feedback between the mixed crowd of computational modelers and theorists, where it was inspiring to see the close interaction between more laboratory oriented, versus solar or astrophysically oriented experts. The remainder of the workshop was scheduled into three themes, where for each case, a tutorial lecture covered introductory as well as modern aspects on the topic. The tutorials were given by Hans Goedbloed on MHD spectroscopy, by Gabor Tóth on numerical MHD, and by Rony Keppens on relativistic MHD. They served their purposes well, and were appreciated by everyone from PhD to expert attendants. For each theme, selected keynote contributions gave full state-of-the-art views on the knowledge progress gained by modern MHD type investigations. Sergei Sharapov explained how experimental campaigns on tokamaks nowadays can identify and map out the individual global modes, as well as see the observational signatures of the continuous part in the spectrum of eigenoscillations of the fusion plasma. Contributed talks gave modern applications of this crowning achievement of MHD theory: from mapping out the wave modes in solar prominences, to providing insights into the link from linear mode knowledge to nonlinear evolutions, in detailed line-tied loop configurations. The keynote talks by Bruno Coppi and by Guido Huijsmans showed complementary aspects of MHD based theory: from analytical models on equilibria and stability in disks and the vicinity of black holes, to fully realistic 3D simulations of tokamak discharges, ready to confront modern diagnostical views on actual experimental discharges. The possibility to model fully the edge localized mode developments in 3D, covering the full plasma volume including the divertor region, opens up many paths towards detailed virtual plasma control. With the first two days covering aspects of tokamak plasma related physics, the shift to solar and astrophysical applications was made midweek. Tamas Gombosi shared the latest achievements on space weather simulations, using the Space Weather Modeling Framework and the BATS-R-US MHD core solver. It is thrilling to see how modern computations, augmented with visualization enhancements, have made their way into the popularization of plasma physics science: a movie used in Imax theatres contains actual simulation results, while the true challenge for scientists remains improving their predictive power. Other modern space weather studies from Predictive Science Inc teamwork also passed the revue.

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The following day, Matthias Rempel covered the latest full radiative-MHD models of sunspot formation and active region evolution. It is fascinating to see the degree of detail nowadays possible due to HPC capabilities: the simulations match all aspects just barely resolved by the best solar telescopes in use today. Shifting towards more remote, astrophysical applications, the presentation by Moira Jardine helped to put the solar magnetism into its wider stellar context. The workshop also covered latest insights into magnetorotational instabilities and their further susceptibility to parasitic modes, and a whole scala of modern codes in use worldwide has passed the discussions (MPI-AMRVAC, SWMF and BATS-R-US, Flash, Pluto, SAC, IPIC3D, JOREK, MURaM, HiFi, PHOENIX and FINESSE, Whisky, . . . ). The later talks in the week then moved our view to even more extreme astrophysics, like the general relativistic models for merging binary neutron stars, and the launch of Gamma Ray Burst related jets in massive star interiors, with the latter being covered in an excellent keynote talk on relativistic outflows by Serguei Kommissarov. The format worked out well and stimulated much interaction. We had specific poster presentation sessions, where in short (10 minute) oral expositions, also the posters were given full attention. The two discussion rounds on challenges in modern and future simulations gave rise to concrete ideas for further collaborative efforts. Together with the social activity (boat trip and dinner), the workshop was a great success, and has been lauded by all participants. The professional support and organization by the Lorentz Center staff is extremely appreciated. Also, the sponsoring from the Lorentz Center, FOM Rijnhuizen, Astronomical Institute Utrecht University, and Centre for Plasma Astrophysics, K.U.Leuven made the whole endeavor financially sound Hans Goedbloed (Utrecht, the Netherlands) Rony Keppens (Leuven, Belgium) Stefaan Poedts (Leuven, Belgium) Alexander Vöegler (Utrecht, the Netherlands)

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Quantitative Methods in Financial and Insurance Mathematics

April 18 – 21, 2011

With this workshop we had the following purposes: 1 Bring together researchers from financial and actuarial mathematics, and discuss the

different stochastic models involved in their (financial, insurance and pension) products, and the different concepts to reduce the risk of losses due to unexpected market conditions.

2 Bring together experts in different numerical techniques (Monte Carlo, PDEs, and quadrature); inform each other about the latest advances and exchange in particular information about the cross-fertilization between these methods.

3 Bring together leading researchers in the Dutch and Flemish communities in the field in order to explore the common grounds in research and education.

4 Invite researchers from the financial and insurance industry to learn about the latest developments in academic research and to interact with the Dutch/Flemish community.

In line with the above, a well-mixed group of about 60 researchers contributed to the workshop from more than 10 different countries. There was a good balance in the group of participants in many respects, in particular in terms of academic/industrial, junior/senior, and male/female researchers. The quality of the presentations was high and stimulated ample discussions. In particular, on Wednesday morning we had a session with mainly industrial researchers from banks. They posed their research questions in an open session, which resulted in a lively interaction between academic and industrial experts. Also, we had a fair amount of junior speakers at the workshop, which worked out very well. Compared to other Lorentz Center workshops, we may have had a large amount of presentations in the week. However, with an active participation of researchers from the financial industry, we considered it important to fill the workshop days, which did not hamper the scientific discussions. These took place also during the coffee breaks, the extended lunch time, the evenings in Leiden, and the successful excursion to the Keukenhof and Katwijk. On the Tuesday, Wednesday and Thursday afternoons we reserved two hours of discussion sessions among the workshop participants. The discussions were guided by a moderator, along the following three topics: • Models in Finance and Insurance, differences and similarities; • Computational techniques, cross-fertilization; • The Dutch/Flemish communities, what can we do together? The discussions were deep and insightful. It was clear that we had a group of motivated expert participants, and the moderation was very accurate and well prepared. This was considered the secret to the success of the discussion sessions. The interaction between scientists dealing with different pricing methods was one of the reasons for some of the special moments in the workshop, where it became clear that existing problems in one area of computational finance were no problem at all for another research area. This was one of the eye openers. A further outcome of this workshop is that a special issue of the Journal of Computational Finance will be devoted to it. As all of our aims have been accomplished we consider the workshop a major success.

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Karel in ’t Hout (Antwerp, Belgium) Cornelis Oosterlee (Amsterdam, the Netherlands)

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Science meets Justice: Forensic Statistics at the Interface

April 26 – 29, 2011

Description and aims: Judicial practice depends in growing measure on knowledge, experience and skills from other areas than law. In particular, it draws more and more from concepts, methodologies and technologies taken from the natural sciences (including the life sciences) and from the behavioral sciences, as well as from information-sciences such as statistics and computer-science. This has led to the invention of a legion of "forensic sciences", and to conflicts concerning demarcation and membership which have only made it harder for juries, lawyers and judges to know "who is the right expert". In this workshop we focused on the conflicts at paradigm level which occur when probability, statistics, genetics, and so on meet the law. We explored and discussed fundamental differences in the way that uncertain information is handled, and in the concept of proof (in general and in the legal context). Tangible outcome: From the workgroup discussions and plenary discussions emerged an outline of a “state of the art” report which was further polished over the subsequent months by email. This report, which was recently finished, is being submitted to the Dutch journal “Expertise en Recht” and will also be submitted to an international journal. A copy is sent to LC with this report, to be appended to the internet information of our workshop. Apart from this, the meeting allowed scientists from extremely varied backgrounds to meet one another and will certainly have helped many participants in extending their scientific networks. Scientific breakthrough? Not as such, but it felt like a breakthrough that there could be such fruitful discussions between people from such diverse backgrounds, and the meeting fitted in the development which has only started in the last ten to twenty years of active involvement from various scientific communities in the processes of law. Aha moments: We got support for the idea that there’s a need for meta-disciplinary approaches, not just inter- and multi-disciplinary. We need common frameworks to make progress in understanding the complex processes within the domain of the theory and practice of evidence. Format of the workshop: We experimented with the notion of working-groups sessions, in which more or less random subsets of the participants discussed some broad questions from the themes of the conference. Some participants brought up their experience of particular cases, others presented a more analytical or theoretical approach. At the end of the week each group summarized its main findings during a plenary meeting, and they were later further integrated in a summing up talk by one of the participants (Ian Freckelton). His great job at this, formed the basis for the “state of the art” report which later has come out of the conference. We found this experiment a success, also through the way it brought participants into closer contact with one another who otherwise might have gone through the week only talking to people they already knew or from their own fields.

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Other comments. The organization, in particular the support from the Lorentz Center staff, was absolutely splendid, and an important factor in making the week a splendid experience for just about everyone, as far as we know. The only hiccup I am aware of was some long drawn out difficulties concerned with how to fill in forms for getting reimbursement for an Australian participant. This really was only a matter of finding the right translation between local terms like BIC and IBAN, and their Australian equivalents. We hope that LC learns from such experiences so that they need not to happen again. Richard Gill (Leiden, the Netherlands) Hans Nijboer (Leiden, the Netherlands)

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Towards Understanding Imaging Data from LOFAR

May 2 – 6, 2011 At low frequencies, the new pan-European radio telescope LOFAR is opening the last unexplored window of the electromagnetic spectrum for astrophysical studies. An important goal of LOFAR is to explore the low-frequency radio sky by means of a series of unique surveys. The main aim of these surveys is to advance our understanding of the formation of galaxies, clusters and active galactic nuclei. These surveys will be carried out and scientifically exploited by a large international science team, consisting of 75 staff astronomers, 23 postdocs and 55 PhD students. Currently LOFAR is in its role-out phase. The Dutch part of the array will be finished in 2011 and will comprise 40 stations distributed over an area of diameter of 100 km. In addition, in 2011 eight stations in a number of European countries (Germany, UK, Sweden, and France) are planned to be operational. Currently many functional elements of the LOFAR imaging system are in place. These elements include: (i) station beam formation, (ii) high speed data transport, (iii) software correlator to produce visibilities, (iv) calibration algorithms, and (v) wide field map making. Although a significant amount of both continued commissioning and technical research will be needed to obtain maps with the theoretical noise levels, the maps that are currently produced already are the deepest ever at these low frequencies. The main challenge for the survey project is to ensure that high dynamic range thermal noise limited images with a stable point-spread function can be made over the entire accessible sky and over LOFAR's full frequency range. The survey team has been and is organizing a series of `busy weeks’. The idea is that a team of astronomers from the survey team attempts to tackle a number of issues related to the challenges just mentioned. The 11th busy week has been held at the Lorentz Center (May 2-6, 2011). During the weekend before this busy week, a large observing campaign was carried out with LOFAR. This resulted in 26 sources being observed at 3 different frequencies. The main aim of the week was to make images of these sources. For the novel users this was an excellent way of getting introduced to the LOFAR system. For the more expert users this data was used to test several of the more advanced data treatment methods. During the first day a number of presentations were given. These gave an overview of (i) the current LOFAR system, (ii) the data already taken and (iii) the status of the reduction software. After the first day work started. The group of novel users was given an extensive tutorial on how to work with LOFAR data. The more expert users concentrated on making deeper maps of the data testing a number of new methods. Furthermore, a group concentrated on studying the methods on how to image LOFAR data taking the beam into account. After the first day, the entire group met twice a day. During the first gathering, it was discussed who should be working on which data sets. During subsequent meetings progress was reported and problems were flagged. Some of these problems could instantly be solved with the help of the more expert users. Part of the last day was devoted to a discussion on next observations. A number of detailed observing programs were designed to be carried out before the summer of 2011.

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Finally, we would like to note that the Lorentz center was ideal for this meeting. The many offices with computers allowed the participants to work very hard on the data. The availability of the common room encouraged many discussions on how to treat the data. The staff of the Lorentz center was extremely helpful and was instrumental to create the atmosphere that is essential to move further with the beautiful, but very challenging LOFAR project. Roberto Pizzo (Dwingeloo, the Netherlands) Huub Röttgering (Leiden, the Netherlands)

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Spin Caloritronics III

May 9 – 13, 2011 “Spintronics” is the science and technology of harnessing the electron spin degree of freedom in circuits and devices in order to realize new or improved technological functionalities. The focus of attention in “Caloritronics” is the control of temperature gradients and the corresponding thermoelectric phenomena in small structures. “Spin Caloritronics” is defined by the intersection of both fields. The first Spin Caloritronics conference has been held at the Lorentz Center in 2009 by the same organizers. It is clear that the Lorentz Center has been an important incubator of the field. In 2009 the international community interested in this emerging field was still rather small. Some arm-twisting and financial support was necessary to attract the main players at that time. In contrast, two years later we had to disappoint many potential contributors since the Lorentz Center was filled to a rim in spite of the limited financial support we were able to provide. Clearly the field has by now outgrown the Lorentz Center and future conferences will undoubtedly be held on a larger scale. We interpret this history as a confirmation of the important role the Lorentz Center can play in advancing science. The workshop was organized in terms of topical sessions with expert invited speakers, and by discussion sessions introduced and moderated by selected leading scientists. We see a clear trend from theoretical speculation and not understood experiments to a more mature interaction of theory and experiments who were now “dancing the tango” according to discussion leader Jairo Sinova. We are happy that several contributors chose this workshop to show and discuss unpublished and sometimes spectacular results. An example is the coherent oscillation of domain walls in a large heat current reported by Stuart Parkin from IBM which was observed in record-high laser-generated temperature gradients. Unexpected cross fertilizations occurred as well. The expert in thermoelectrics, Jos Heremans from the Ohio State University, was excited by the ‘fantastic’ theoretical estimates of the spin caloritronics figures of merit of magnetic thermal engines as estimated by Yaroslav Tserkovnyak from UCLA. This implies that for the first time we have found a realistic application perspective of our field, e.g. in thermopower generation and cooling at cryogenic. While the Keukenhof excursion was a bit of a disappointment since most of the flowers were gone because of the dry weather of the previous few weeks, the BBQ dinner at the North Sea beach was blessed with a spectacular sunset. All participants have been impressed (again) by the high quality of the Lorentz Center’s premises and expressed their gratitude for the excellent support by the highly motivated staff – in spite of the extra strain on the resources due to the large number of participants. We gratefully acknowledge the financial support by the Lorentz Center and by the Kavli Institute of NanoScience Delft. Gerrit Bauer (Delft, the Netherlands) Sadamichi Maekawa (Tokai, Japan)

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Coherent Structures in Dynamical Systems

May 16 – 20, 2011 Central in the study of dynamical systems is the search for invariant sets or coherent structures that organize long-term behavior. Examples of coherent structures include periodic orbits, invariant manifolds, homoclinic orbits, and invariant tori. By performing appropriate local analyses around these coherent structures and studying how they fit together, a “skeleton” of the dynamics may be sketched. The specific characteristics of such a skeleton depend on the nature of the vector field at hand. Performing these analyses is only feasible when explicit knowledge of the vector field is available. But in many important problems such knowledge is not available, presenting a great challenge. An example is the motion of elementary fluid particles in a geophysical fluid. The time-aperiodic character of the mostly-turbulent velocity field, in addition to the finiteness of the time interval of the data, further complicates the possibility of drawing a skeleton of the Lagrangian dynamics. In recent years, new techniques have been devised to help unveil dynamical skeletons from limited data sets. These techniques have been mainly applied to unsteady flows in two-space dimensions, leading to a major breakthrough in the physics of mixing; their application to unsteady three-dimensional flows remains largely unexplored. For instance, it remains to be determined if there exists a rigorous theory that can be used as a foundation for coherent structures underlying such flows. An accompanying challenge is the appropriate visualization of coherent structures evolving in three-space dimensions and time. The aim of this workshop was to bring together experts on the study of coherent structures in dynamical systems, and researchers with interests in the application of dynamical systems methods to unveil coherent structures in dynamical systems that describe specific physical systems including, but not restricted to, fluid systems. It was expected that applied dynamical systems researchers benefit from the expertise of theoretical dynamical systems researchers as a result of this gathering. At the same time it was expected that new theoretical research in dynamical systems be inspired by specific applications of dynamical systems methods. This workshop was considered a success if, in addition to promoting the collaboration between applied and theoretical dynamical systems researchers, young researchers got interested in this new and exciting area. New developments in theoretical dynamical systems research and results from the application of dynamical systems tools were presented in the workshop by both senior investigators and young researchers, including a good number of graduate students. Some of the new theoretical developments were inspired by needs of advancing applied research, mainly in the area of fluid dynamics. Additional needs of advancing theoretical research were brought to the attention to the theoretical community, which are expected to stimulate further interactions among theoretical and applied researchers that lead to new advancements in the study of coherent structures in dynamical systems. Overall, it can be confidently stated that the goals of the workshop have been reached. Francisco Beron-Vera (Miami, USA) Henk Broer (Groningen, the Netherlands) María Olascoaga (Miami, USA) Thomas Peacock (Cambridge, United Kingdom)

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The Motivic Fundamental Group

May 23 – 27, 2011 The topological, the algebraic and the crystalline fundamental groups along with their representations can be thought of as different realizations of one underlying motivic object. Deligne and Goncharov endowed the unipotent part of the group ring of the fundamental group with the structure of a motive. Faltings and Hadian have successfully applied an abstract theory of motives to the fundamental group and have obtained strong new results in diophantine geometry. The aim of this workshop was to present these recent developments to a larger audience of arithmetic algebraic geometers, in the hope that the participants learn how to use the motivic fundamental group to attack classical questions in diophantine geometry, arithmetic algebraic geometry and even physics. The program consisted of three series of three talks by Goncharov, Faltings and Hadian and six individual talks by Kim, Furusho, Hain, Esnault, Bloch and Stix. In the coffee and lunch breaks and in the evenings there was ample time for discussions between the participants, in a stimulating atmosphere. There were about 30 registered participants, mainly from outside the Netherlands. The organizers had hoped that this beautiful subject would attract the interest of a larger group of arithmetic geometers in the Netherlands. The organizers and the participants were very enthusiastic about the facilities offered by the Lorentz Center. They also gratefully acknowledge the financial support by the Lorentz Center and by the Foundation Compositio Mathematica. Spencer Bloch (Chicago, USA) Dale Husemöller (Bonn, Germany) Jan Stienstra (Utrecht, the Netherlands)

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Molecular Logic

May 30 – June 2, 2011 Scientific Topic Molecular logic is a highly multi-disciplinary field involving biologists, chemists, physicists and computer science engineers. The aim of this workshop was to bring these communities together focusing on the common problems and goals, in particular: parallelism, concatenation, and scalable molecular finite-state machines. Speakers M. Atature, Y. Benenson, A. Credi, J.R. Heath, C. Joachim, S. Kaxiras, R. D. Levine, S.J. van der Molen, K. Ohmori, P. Adriaans, G. Scholes, M. Stojanovic, M.J.J. Vrakking, D. Williams. Workshop This workshop focused at the interface between molecular optics and chemistry impacts on implementations in the solid state as well as biological applications aimed at nano-medicine and intelligent sensors. Biologists, chemists, physicists and computer science engineers attended the workshop which lead to active cross communication and fruitful exchange of ideas. The workshop brought these communities together and focused on three models of computation that can be implemented by the different sub-communities: • Parallelism: Inherent parallel logic operation was discussed in terms of optical

measurements on ensembles of molecules and proposed electrical implementations. Parallelism as implemented in biological systems was presented and the opportunities that bio systems open for the other fields were discussed and their feasibility assessed. The conclusion is that in terms of number of variables and complexity, transposing bio based implementation to chemical and physical systems is very challenging.

• Concatenation: It became obvious that concatenation is the key obstacle encountered by all molecular and atomic implementations. Possible solutions and the limits of the different approaches were discussed. One solution is to use multivalued logic which is inherent to the molecular scale and this option was discussed. Limitations of molecular logic in general and how to efficiently interfacing with the macroscopic world was a long discussion point.

• Scalable molecular finite-state machines: Together with concatenation scalability was the key issue. The attendees agreed that the field needs to go beyond the single device level and needs to address scalability, at least on the connectional level.

The workshop led to the common realization that molecular logic can propose efficient implementation at the single device level on various atomic and molecular systems of increasing complexity, but needs to show how it can compete with traditional technologies in a realistic manner, i.e. not only focus on device implementations. The different communities realized that they all face common problems and need to communicate the state of the art of the field in a more concise and realistic manner. The scientific exchanges were greatly facilitated by the format of the workshop, leaving ample time for discussions, and the smooth organization provided by the Lorentz Center. Francois Remacle (Liege, Belgium) Sven Rogge (Delft, the Netherlands) Itamar Willner (Jerusalem, Israel)

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4th European Women in Mathematics Summer School

June 6 – 10, 2011 The aim of the summer school was to provide a stimulating intellectual environment for PhD students from different countries and different mathematical disciplines to learn new mathematics (outside the scope of their own research) and to meet new colleagues. The summer school was especially aimed at encouraging female students and researchers at the beginning of their career, but also male students were very welcome to participate. Participants By contacting the mathematics departments in the Netherlands, the EWM coordinators and our personal contacts at European universities, we gathered 180 e-mail addresses of young female mathematicians, whom we all invited to the summer school. In the end 30 students participated in summer school. Scientific program The scientific program consisted of mini-courses on the three topics: Logic, Geometry and History of Mathematics. The Logic session started off with a general introduction into the central concepts of the field. Thereafter the logic speakers covered the following topics: the relation between logic and automata theory, certified mathematics and model theory. Due to absence of the scientific committee member, there was no general introduction into the Geometry session. However, this allowed us to schedule two talks on symplectic geometry, enabling the speaker to go into some more depth. The other talks in the Geometry session covered directed topology and its applications on computer science, and real algebraic geometry. This last lecture was closely related to the model theory talk, thereby nicely connecting the Geometry and the Logic session. The lectures in the history session gave an account of the role of women in the History of Mathematics in the 18th, 19th and 20th century. The talks portrayed several women who were doing mathematics either in academia or in domestic spaces. Moreover, the existence of barriers for women who wanted to enter academics throughout the centuries was discussed, the barriers being in the scientific institutions themselves or in the thought system of people. To get the students actively involved, there were problem solving sessions in Logic and Geometry and a mini workshop on History in Mathematics. The problem sessions were very interesting and diverse. The lecturers had prepared exercises at various levels, so that the sessions were of interest to both students with a background in the field and newcomers. The sessions merged very well with the talks and promoted plenty of discussions among the participants. During the mini workshop on History of Mathematics the participants read original mathematical articles, answered questions to these articles and in the end presented their work to the other participants of the mini-workshop. This workshop was a success; the students were very enthusiastic about working with the articles and presenting their work. Another activity to encourage discussions between the students was the ‘present yourself session’ during which the participants were divided into small groups, accompanied by a senior researcher, and gave a mini-talk about their current research. The whole session proceeded smoothly and the participants were pleased with the advices received and, perhaps more importantly, enjoyed very much each other's talk. It was an opportunity to broaden their view and get inspiration. One of the participants said: "Thank you for this

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great summer school. I feel refreshed; now I can go back to my work very motivated. I liked the mini-talks we gave to each other; that's where I could step back and look at mathematics as a whole. It was great!” Gender issues During the summer school there were two sessions about gender issues. Both sessions consisted of a presentation followed by a panel discussion. The first lecture was about gender practices in recruitment and election of full professors and the under-representation of women in senior academic positions in the Netherlands. The second talk discussed the fact that few girls choose to study Science, Technology, Engineering and Mathematics. Statistical data from Norway, UK, Slovenia, Italy and Denmark were shown, and some examples of stories of Norwegian girls studying these subjects were given. The panel discussions after these talks were very lively, addressing diverse aspects of gender issues in academia, and the participants of the summer school got actively involved in the discussions as well. Overall result The summer school has been an inspiring and motivating week, as also became clear from some of the responses we got from participants. They said: ‘I am more motivated as a woman mathematician’, ‘I felt lonely at my department, with hardly any female colleagues, I was very happy to discover that there are actually female mathematicians’ and ‘I was very inspired this week to do new stuff’. One of the students was still at the bachelor level, for her it has been very useful to discuss the possibilities of doing a master in France, England or The Netherlands with the senior researchers. Some students mentioned that it would have been nice if there were more applied talks as well. This was the case at the previous summer school, we choose to cover history of mathematics this time instead. It might be good to cover a more applied topic again at the next summer school. Compared to the previous summer school we cut down on the gender discussion sessions and instead introduced the problems solving sessions, mini-workshop on history and presentation sessions. The participants enjoyed the fact that they were actively involved and many mentioned they learned a lot from the feedback on their presentations. Hence we would definitely repeat this interactive set-up in a next edition. Dion Coumans (Nijmegen, the Netherlands) Andrea Hofmann (Oslo, Norway) Janne Kool (Utrecht, the Netherlands) Erwin Torreao Dassen (Leiden, the Netherlands)

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Black Hole Answers for Condensed Matter Questions

June 14 – 17, 2011 Description and Aim The aim of this workshop was to explore and capitalize on the opportunities provided by the novel application of gauge-gravity duality to strongly coupled condensed matter systems. This new powerful mapping arises from string theory and has the ability to relate exceedingly difficult fermionic condensed matter questions to potentially tractable problems in an anti-de Sitter black hole background. The immediate goal was to achieve an active cross-communication between condensed matter theorists specializing in fermionic quantum criticality, pioneering string theorists, and forefront experimentalists in quantum critical systems. Outcome The workshop has been hailed by many participants as a great success. The rapid developments in the field had left a number of open questions and paradoxes. The collective gathering of the forefront researchers gave us a wonderful opportunity to flesh these out and resolve a number of them. For instance, it became abundantly clear that one of the proposed gravity descriptions for the dual a Fermi liquid – the charged neutron star – had to describe additional degrees of freedom as well. This led directly to a proposal of a Fermi liquid using gauge-gravity duality which removed these additional degrees of freedom (S. Sachdev A model of a Fermi liquid using gauge-gravity duality, Phys.Rev. D84 (2011) 066009). At the same time the intense discussions crystallized in the thorough realization that these additional degrees of freedom are essential to understand the so-called Lifshitz scaling behavior in thermodynamic quantities. Interestingly, there was an intense discussion during A. MacKenzie’s presentation of his experimental results whether this is what is seen in the data. Other examples of very fruitful discussions related whether more fundamental string theory models are actually able to reach the parameter ranges needed to describe the wonderful new fermionic physics discovered with gauge-gravity duality, and at any stage the possible connections with experiment were intensely explored. The latter discussions in particular were one of the primary goals of this workshop. Workshop Format and Comments The format with plentiful discussion time proved essential to the success of the workshop and we received wide praise by all the participants. Their praise extended as widely to the whole Lorentz Center organization. As an organizer I have mentioned this success and praise to a number of colleagues interested in organizing a workshop. I shared with them this very blueprint which relies so much on the excellent input of the Lorentz Center Staff and Organization. A sign of the appreciation for such a Lorentz Center workshop is that I am aware of at least two workshops in 2012 (Effective Field Theories in Inflation, Holographic Thermalization) that have followed from this. Sean Hartnoll (Cambridge, USA) Hong Liu (Cambridge, USA) John McGreevy (Cambridge, USA) Sung Sik Lee (Hamilton, Canada) Koenraad Schalm (Leiden, the Netherlands) Jan Zaanen (Leiden, the Netherlands)

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Fluctuations and Response in Active Materials: From Driven Granular Systems to Swarming Bacteria

June 20 – 24, 2011

Description and Aims The aim of the workshop was to bring together leading theoretical, computational, and experimental scientists in the fields of granular/soft materials and active matter for two key objectives. First, we wanted to identify fundamental open questions that are common to both nonliving, physical systems such as granular media and active, living systems. Some of the important questions that emerged from the workshop include: 1) what are the “universal” properties of active matter that determine large-scale behavior, 2) can an improved understanding of active living matter lead to design strategies to prevent unwanted jamming and glassy behavior in granular, colloidal, and other physics systems, 3) to what extent can bio-activity, collective behavior, and pattern formation in biological systems be explained by physical forces, response, and fluctuations, and 4) what are the similarities and fundamental differences between living matter and driven dissipative systems. Second, we wanted to encourage international collaborations among experimentalists and theorists in granular and active matter to develop interdisciplinary research programs to tackle these open questions. The workshop attracted 41 participants in addition to the seven organizers. The organizers obtained funding from the National Science, Brandeis University and Yale University. Outcomes The Workshop led to several outcomes: 1) The James A. Krumhansl School and Symposium on Unifying Concepts in Materials was held at the Jawaharlal Nehru Centre for Advanced Scientific Research and National Centre for Biological Sciences in Bangalore, India, co-organized by Madan Rao, as a follow-up meeting to the “Fluctuations and Response in Active Materials: From Driven Granular Systems to Swarming Bacteria” Workshop in late January into early February 2012; 2) Several of the organizers submitted grant applications on focus topics of the Leiden workshop including “Focusing and Controlling Acoustic Energy using Metamaterials” submitted to the Defense Threat Reduction Agency by Corey O’Hern and Mark Shattuck and “Friction as an emergent property in unconsolidated media” submitted to the Department of Energy by Bulbul Chakraborty, Narayanan Menon, and Corey O’Hern; 3) Follow-up Invited Sessions at the American Physical Society’s March 2012 Meeting on “Hydrodynamics and Microstructure: From Single Self-Propelled Particles to Active Soft Matter” and “Active Matter and Dynamical Systems”; and 4) the Topical Group on Statistical and Nonlinear Physics now has a permanent sorting category “Statistical Mechanics of Active Matter and Biological Systems” in addition to Categories 03.7 Disordered and Glassy Systems, including Jamming and 03.8 Granular Materials. In addition, several of the organizers anticipate submitting proposals to the National Science Foundation and other funding sources to support research at the interface of soft, active, and granular matter among researchers in the US, Europe, and India in the near future. Workshop Format The workshop format included 14 speaker/discussant sessions (70 minutes); nine hot-topic talks (30 minutes per topic), two breakout sessions (70 and 40 minutes), two poster sessions (40 and 60 minutes, a final discussion (90 minutes), and midweek dinner at Prentenkabinet. The effectiveness of the speaker/discussant sessions varied with the pair, i.e. those that had

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discussed their sessions before the meeting delivered much better sessions than those that had not. The organizers would be interested in methods for increasing discussion and participation of the workshop attendees. The food and location of the Workshop dinner were excellent. Bulbul Chakraborty (Waltham, USA) Martin van Hecke (Leiden, the Netherlands) Jean-Francois Joanny (Paris, France) Narayanan Menon (Amherst, USA) Corey O’Hern (New Haven, USA) Sriram Ramaswamy (Bangalore, India) Madan Rao (Bangalore, India)

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Analysis and Visualization of Moving Objects

June 27 – July 1 2011 Description and aim Research into movement of all sorts is an area which has seen increasing interest in recent years. On the one hand, researchers in diverse domains such as transportation research, animal ecology and epidemiology are faced with ever increasing possibilities to collect large volumes of data, often in real time. On the other hand, researchers in domains such as computing science, geographic information science and visualization are actively developing methods to analyze such data and extract useful information. The workshop’s key aim was to bring together researchers from different domains, and in so doing provide a forum for discussion of advances in research on movement data. In so doing, the workshop sought to build on advances made through a range of recent initiatives, including the momentum created by the MOVE action of the COST Program which part-funded the workshop (http://move-cost.info). The main goals of the workshop were threefold. Firstly, we wanted to facilitate the exchange of knowledge among quite diverse disciplines. Secondly, we aimed to identify important cross-cutting concerns and research questions culminating in the formulation of a research agenda for the coming years. Finally, we hoped to stimulate and encourage new research directions and collaborations. Workshop format The workshop was organized to encourage and enable discussion, and as such had three distinct strands of activity. The first strand of activity took the form of six keynote lectures that were presented over the course of the week, three from researchers active in tracking a wide variety of animals and three from those involved in different domains of methodological research. Each talk was scheduled for around 45 minutes, allowing ample time for discussion, and the speakers were explicitly asked to formulate what they felt were key research challenges for the field in the coming years. The second key strand of activity involved a data challenge, which participants were invited to complete in advance of the workshop. Participants were provided with access to data describing the movement of gulls by one of the workshop organizers, and given a set of so-called basic questions as well as more advanced interpretative challenges. Examples of basic questions included identifying the number and length of trips taken by individual gulls, while more complex tasks involved, for example, the identification of common shared paths used by the gulls. A total of nine groups took part in the data challenge and submitted results before the workshop, and on the first day these results were presented to all participants. The data challenge proved particularly useful in providing a common ground for the discussions which followed, with the majority of workshop participants having, either through their own research or the challenge, the opportunity to explore real movement data and discuss these with domain experts. The third strand of activity took the form of group discussions and work which was carried out throughout the workshop. An initial discussion following the presentation of the data challenge identified five themes:

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Uncertainty and granularity: this group discussed the influence of, for example, sampling interval on the information derived from individual tracks, and explored how previously unused GPS data might be exploited to help in the extraction of behavioral data.

Integrating context: Contextual information, such as that relating environmental parameters (e.g. wind speed) to individual behavior is key to expert interpretation of movement data. However, methods to sensibly up and downscale environmental data, and other contextual clues, to the scale of individual tracks are still in their infancy.

Scale and scalability: Typical representations of movement focus on traditional geometric representations of space, which typically result in over plotting and limited ability to explore individual events in very large volumes of data. This group developed a prototype visualization, using techniques from visual analytics, to explore in more detail stopovers in space and time during goose migration.

Space and time: Many approaches to analysis of movement data privilege either space or time, leaving an increasing need for methods which seek to both quantify and visualize behaviors in space and time simultaneously.

Grouping and clustering: Much methodological research has been expended on the development of methods to extract interesting and relevant patterns from movement data, and to cluster similar patterns. However, typically such research is carried out in isolation, and the group discussed how applications could be developed which would be used by much larger communities, for example through the development of web services for Movebank (www.movebank.org).

Each group reported twice to the whole workshop during the week, and all groups had the opportunity to work intensively on real data. Workshop outcomes The data challenge participants have agreed to work together to prepare and draft a paper on the results of this exercise, most likely for submission to Methods in Ecology and Evolution. A meeting report has also been submitted to Biology Letters for review and potential publication(Shamoun-Baranes et al, 2011). A number of the working groups agreed to continue working on the problems identified, and more papers are likely to result from these new links. Through MOVE funding it is likely that researchers involved in the work-shop will undertake short terms scientific missions to continue collaboration. Furthermore, a set of key references suggested in the keynote lectures will be summarized and added to MOVE’s bibliographic database (http://www.move-cost.info/refbase/). Evaluation The workshop broadly succeeded in all of its goals, bringing together a diverse group of researchers, providing an opportunity to identify cross-cutting concerns and encouraging new research directions. The data challenge and generous time allocated to plenary and group discussions ensured that participants had ample time to familiarize themselves with and explore real movement data, in an enjoyable and stimulating atmosphere. Acknowledgement The Lorentz Center is thanked for facilitating this workshop, and the staff of the Lorentz Center for their assistance in arranging and running of the workshop. The workshop was partially supported by the ESF COST action IC0903 MOVE (Knowledge Discovery from Moving Objects). Ross Purves (Zurich, Switzerland)

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Judy Shamoun-Baranes (Amsterdam, the Netherlands) Bettina Speckmann (Eindhoven, the Netherlands) Daniel Weiskopf (Stuttgart, Germany)

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Extreme Value Statistics in Physics and Beyond

July 4 – 8, 2011 The goal of the workshop was to bring together researchers from different backgrounds to discuss fundamental properties of extrema of strongly correlated random variables, to establish common features of systems of different origin, to elaborate on finding a unifying language for the description of these systems, and to discuss applications in mathematics, physics, astronomy, finance and climatology. Five core topics were included: (1) Extreme value and record statistics of fractional Brownian motion. (2) Extreme distributions in nature. (3) Extreme value statistics and theory of random matrices and operators. (4) Extreme distributions on partitions. (5) Models of stochastic growth and extreme values. A total of 40 researchers attended the workshop, including some 10 junior researchers. A total of 20 talks were presented. In addition, the program included parallel discussions in small groups on each of the five core topics, as well as a plenary round-table discussion, moderated by Aernout van Enter and Joachim Krug. Both events added a lot to the workshop, generated fruitful information and original points of view, and are recommended by the organizers as an efficient way of communication on a more strategic and exploratory level. Some of the participants expressed the opinion that it would have been better to organize the topical discussions consecutively and not in parallel. One scientific highlight: during the workshop the central role of the Tracy-Widom distribution became all apparent. Apart from the statistics of extreme eigenvalues of random matrices, this distribution shows up in many different areas, e.g. growth models, branching processes, and random walks interacting with themselves and with their environment. The talk by Celine Nadal was particularly impressive, since her approach made the derivation of the Tracy-Widom distribution via orthogonal polynomials almost elementary. The discussions that followed, with comments by Bernard Derrida, Victor Dotsenko and Satya Majumdar, gave the participants the feeling that the universality of the Tracy-Widom distribution can finally be fully understood. Another eye-opener was the presentation by Victor Dotsenko, who explained how the Tracy-Widom distribution emerges from the weak interaction scaling behaviour of the partition function of the directed random polymer in random environment, whose analysis has illuded researchers for over 20 years. Another eye-opener was the presentation by Victor Dotsenko who, reporting on his work and related work by Calabrese, Le Doussal and Rosso, explained how the Tracy-Widom distribution emerges from the weak interaction scaling behavior of the partition function of the directed random polymer in random environment, whose analysis has illuded researchers for over 20 years. This link also appears in the recent work by Amir, Corwin and Quastel. The relaxed program, typical for Lorentz Center workshops, with ample time between presentations and with office space made available for small working groups, helped much to increase the interaction. The support and the enthusiasm of the staff of the Lorentz Center was perfect. The organizers are grateful for the perfect arrangement that made this workshop into a most efficient meeting. Yan Fyodorov (Nottingham, United Kingdom)

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Frank den Hollander (Leiden, the Netherlands) Sergei Nechaev (Paris, France) Holger Rootzen (Goeteborg, Sweden) Senya Shlosman (Luminy Marseille, France)

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Transgenes Going Wild? Risk Assessment of Transgene Introgression

from Crops into Wild Relatives

July 11 – 15, 2011 Description and Aim We could not survive and have colorful lives without domestic plants and animals. The Food and Agriculture Organization of the United Nations (FAO) predicted that we may need 70% more food by 2050 with the increasing human population, diminishing resources and shifting dietary patterns and longevity. The rapid development of biotechnology offers new opportunities for improving food security. Novel traits can be introduced more efficiently and swiftly into crops by genetic engineering than by conventional crop breeding technology. However, transgenes could escape from crops into wild relatives via gene flow and introgression. This may have unwanted ecological and evolutionary consequences in wild populations, depending on the nature of the transgene and its effect. The European Food Safety Authority (EFSA) will soon, probably in 2012, update the guidance on Environmental Risk Assessment (ERA) of Genetically Modified (GM) plants. Therefore, the objectives of the workshop were to: 1) Present relevant research findings about transgene introgression risk assessment; 2) Discuss the most effective methodology for transgene introgression risk assessment; 3) Make suggestions for risk assessment frameworks. The workshop The workshop gathered 40 participants in the Lorentz Center including ecologists, molecular biologists, population geneticists, environmental scientists, mathematicians and policy makers from seven European countries, United States and China. In particular, policy makers from EFSA attended the workshop. Dr. Ellstrand from University of California at Riverside, who initiated studies about crop-wild hybridization and its consequences 10 years ago, gave a nice summary talk of this field. New case studies in carrot, oilseed rape, radish, rice, and lettuce were presented. New molecular methods were introduced for detecting crop-to-wild introgression in nature. The roles of mathematical modeling in understanding the mechanisms of introgression and in estimating the risks of transgene introgression were discussed. The new EFSA guidance for risk assessment of GM plants was introduced and discussed. There were lively active interactions among the participants during the workshop. Many new ideas were produced in the group discussions. New cooperation networks have been established. Outcome In general, we agreed that hybridization and gene flow between crops and their wild relatives had occurred for a very long time since the beginning of the crop domestication (10 thousand years ago). Gene flow itself is a neutral process and does not need to have adverse consequences. Therefore, from the point of view of risk assessment, where risk = hazard x exposure, gene flow is not necessarily a risk. Introgression is the permanent incorporation of genes from one set of differentiated populations into the other. Introgression involves not only hybridization and gene flow but also the genes need to be incorporated into new populations. Scientists tended to believe that spontaneous introgression had occurred from many crops into one or more wild populations somewhere in the world though solid evidence, excluding alternative explanations, was rare. With the new

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high-throughput sequencing and genotyping technologies, conclusive evidence about crop-to-wild introgression can be found. Still, introgression may not be evolutionarily or ecologically significant leading to a possible “hazard”. Crop-to-wild introgression usually results in increased genetic diversity of wild populations, but only occasionally leads to the evolution of increased weediness/invasiveness or extinction risks. There were well-substantiated reports of more than 14 transgene events “escaping” into the “wild” but they were mostly in agriculture fields or along the road sides under strong human disturbances. Crop-to-crop transgene flow generally should occur more often than crop-to-wild gene flow and should receive more consideration. We should focus more on the possible “hazard” of introgression for risk assessment. Mathematical modeling can provide powerful tools for risk assessment and management but we need to be very careful not to overestimate the power of modeling. For regulations, there is a tendency to ask for more detailed data for risk assessment and management, but we need to keep in mind that what we need to know and what data are indeed necessary. Based on the outcomes of the workshop, we decided to write three publications together to summarize the workshop and to provide guidance for both scientific researchers and regulations in the future. Acknowledgement We are very grateful to the Lorentz Center for great supports to our workshop, especially Corrie Kuster, Sietske Kroon, Henriette Jensenius and Mieke Schutte. We thank all participants for their contributions to the workshop, all the brilliant ideas in the presentations of the speakers and during the discussion sessions. We thank co-organizers Klaas Vrieling, Wil Tamis, Cilia Grebenstein, Atiyo Ghosh and Suzanne Kos, and session moderators Dr. Peter H. van Tienderen and Elze Hesse et al. for their great jobs to make the workshop go smoothly. Special thanks to Prof. Norman Ellstrand for the excellent review of the field and leading many of the discussions during the workshop. The workshop was supported by funds from the Lorentz Center, Netherlands Organisation for Scientific Research (NWO), and the research program “Ecology Regarding Genetically Modified Organisms” (ERGO). Detlef Bartsch (Berlin, Germany) Hans Bergmans (Bilthoven, the Netherlands) Patsy Haccou (Leiden, the Netherlands) Tom de Jong (Leiden, the Netherlands) Bao-Rong Lu (Shanghai, China) Jun Rong (Leiden, the Netherlands) Geert De Snoo (Leiden, the Netherlands) Allison Snow (Columbus, USA)

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Discrete Integrable Systems

July 18-22, 2011 Description and aim The workshop targeted the following five themes: 1. Multi-Dimensional Consistency, Lagrangian Forms: Can we extend the classification with respect to multi-dimensional consistency, to include non-scalar cases? What is the significance of the new variational principle connected to Lagrangian forms, e.g. in physics applications? 2. Symmetries, Integrals, Conservation Laws, and Symplectic Structures: What are the relations between (the number of) symmetries, integrals and conservation laws? Can one decide on symplectivity without deriving a symplectic structure? How to systematically construct symplectic structures? 3. Reductions and Solutions: How to construct (explicit) solutions for periodic reductions, Painlevé reductions, or solutions of other type, i.e. finite gap, rational solutions. 4. Detection and Testing of Discrete Integrable Systems: What are currently the most effective methods? Can we identify relations between different notions of integrability, e.g. growth versus consistency? 5. Geometric Approaches to Discrete Integrable Systems: Algebraic geometry has been successfully applied to the Painlevé equations, and to the QRT maps. Can this be extended to higher dimensional mappings, and to lattices? The workshop also aimed to initiate new research and research collaborations. Format Each of the 5 days of the conference was devoted to one of the 5 themes above, with talks in the morning and a moderated discussions in the afternoon. Discussion • Notable progress has already been made on points 1 and 2 above (e.g. Lagrangians for

the MBSQ system), and several new research collaborations have been started. • The moderated discussions worked very well. • The workshop attracted a significant number of starting/early career researchers. It has

been very gratifying to observe the synergy, interaction, and enthusiasm of this group. • The organizers are grateful to the KNAW, to NDNS+, to the Australian Centre for

Mathematics and Statistics of Complex Systems (MASCOS), and to the Lorentz Center for much appreciated financial support.

Suggestions: • The restricted web site for the organizers could contain more information, eg regarding

the budget. • Last but not least, restaurant Allemansgeest was a perfect venue for the conference

dinner. Peter van der Kamp (Victoria, Australia) Frank Nijhoff (Leeds, United Kindom) Reinout Quispel (Victoria, Australia) Jan Sanders (Amsterdam, the Netherlands)

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Computational Neuroscience and the Dynamics of Disease States

August 8 – 12, 2011

The goal of our workshop was to bring together theoreticians (computational modelers as well as experimental neuroscientists) and clinicians in order to bridge the large gap between those fields and improve the understanding of the basis of dynamical diseases The interest in the workshop was apparent from the background of the 51 participants which included mathematicians, physicists, engineers, neurologists and neurosurgeons, many of them leading scientists in their field. As the leading feature we organized duo-talks for a physician and a experimentalist/ theoretician. Several stimulating examples of fruitful cooperation were presented that beautifully illustrated what can be achieved when clinical needs and computational modeling are matched in an interdisciplinary way. In addition five general lectures reviewed various aspects and approaches of computational neuroscience in a clinical context As expected, the range of topics in the meeting varied widely: • understanding the role of excitation, inhibition and network structure in dynamic diseases,

-in particular epilepsy, migraine and Parkinson’s disease; • improve our insight in the basic mechanisms underlying deep brain stimulation in the

basal ganglia for the treatment of Parkinson’s disease; • develop a culture of biophysical and mathematical modeling of neurological diseases that

will spark further interest from these communities and from clinicians; • to lever funding from the EU via grant applications and translate results from basic

research on the dynamics of disease states into clinical neurology The poster session on the first day evoked stimulating discussions and gave ample attention to the eleven PhD students that attended the workshop. Thursday afternoon was devoted to informal discussions on Parkinson’s disease, epilepsy, large scale computation and optimal models for clinical questions. Key questions for deep brain stimulation were put forward. The discussion on the modeling was particularly lively, resulting in a long list of requirements for relevant models. A need for tools to compare detailed large scale models with coarse grained models was identified. Participants found the meeting successful and a step in the direction of our ambitious goals. It will further interdisciplinary collaborative research in clinical neuroscience. We are grateful for the support of the Lorentz Center and for our sponsors: The UK Mathematical Neuroscience Network, Het Swammerdam Institute (UvA) and MIRA (UT). Stephen Coombes (Nottingham, United Kingdom) Stephan van Gils (Enschede, the Netherlands) Michel van Putten (Enschede, the Netherlands) Wytse Wadman (Amsterdam, the Netherlands)

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Standards in Emotion Modeling

August 15 – 19, 2011 Intro This workshop was about computational models of (a) emotion generation, and (b) the effects of emotion on cognition, but from a particular angle that emphasizes the interplay between emotion psychology and computational modeling. In short, the workshop was about computational modeling of the interplay between affect and cognition, i.e., computational modeling of affective processes (CMAP). Workshop aim The workshop’s aim was to better understand the process of computational modeling of emotion, so that the resulting models are traceable (testable), comparable with other models, and so that the psychological grounding of the models is clear (including where the grounding breaks down). These things are needed for two main reasons. First, the diversity in computational models of emotion will continue to grow, and diversity is good if we understand what the exact “diversity” is, and how the models relate to each other in detail. This will help us to better decide what kind of emotion model is needed for what context. Second, if computational models of emotion are viewed as mechanisms-oriented instantiations of psychological theories of emotion, then these should be able to tell us something about emotion in the human species and other animals and generate testable hypotheses, but only if we know exactly how the model is built, and how it is grounded. The SEM2011 workshop aimed to advance the discussion of these two aspects. Workshop format The workshop was visited by 25 participants from 7 countries, and has a good mix of senior and junior researchers and psychologically oriented and computation oriented individuals. The workshop consisted of plenary sessions of invited speakers and submitted paper presentations, but the better part of it was filled with lively discussions around the main workshop topics including psychological grounding, model validation, standardization of modeling process, and “super models” (models that include different affective phenomena, such as the interplay between mood and emotion). We thank all of the participants for their active attitude! Outcome A major outcome of the workshop is the realization among all participants that computational models of emotion are psychological experimental tools to gain insight in emotion, and that many of the details needed for developing these models simply are not available in emotion psychology. Hence, instead of asking for these details from psychologists, the models should bring insight. Further, the workshop identified major challenges that need to be addressed to better understand the process of computational modeling of emotion. These include: what are the benefits and pitfalls of taking either a domain specific or an abstract approach; what are issues in using games-like scenarios as complex stimuli to evaluate models and elicit emotions; what are the issues in using a common decomposition of the appraisal process for the evaluation of models, understanding appraisal theories, or for providing a common implementation framework for theories. Can we agree on this decomposition; what are the different types of goals, and how do these relate to utility, desire, desirability, (social) values, and appraisal; can we identify a protocol for the development of a CMAP (why do you need the model, why select a particular appraisal theoretical basis, ways of validating, etc…) with

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associated questions/assumptions that might be needed for each step towards implementation; what is the function of the model and what are the designer’s goals; what are best practices towards computational modeling of affective processes; what is the relation and interplay between naïve (normal peoples’) and scientific models of emotion. Finally, with respect to the intrapersonal nature of emotion we agreed on the following point of view, that seemed to best represent both the psychologists’ views as well as the computational modelers’ interpretations. Emotion refers to the descriptive label for particular patterns of joint activity of multimodal constituents (e.g., valence, expression, action, arousal, appraisal). The experience of emotion refers to the (conscious) detection (global availability) of such patterns. The intrapersonal function of emotion is a complex feedback signal for a(n) (synthetic) organism to adapt its behavior; each emotion has a different kind of signaling function, some are about anticipated events (fear) while others are about past events (anger). Acknowledgements The Lorentz Center was great. Of course it gave important financial support, but on top of that it facilitated everything with friendly, helpful and very available personnel. Further we would like to thank the TU Delft (Catholijn Jonker) and the VU (Jan Treur) for their additional financial support to cover extra travelling costs. Finally, we sincerely thank all the participants for the lively discussions filled with emotion (in all thinkable forms and quality). Tibor Bosse (Amsterdam, the Netherlands) Joost Broekens (Delft, the Netherlands) Stacy Marsella (Playa Vista, USA)

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Strongly Disordered Superconductors and Electronic Segregation

August 22 – 26, 2011

Description and Aim Apart from the interesting fundamental problem of competition between strong localization and superconductivity, disordered superconductors are interesting materials to study quantum phase slip processes as well as for use in the detection of faint astronomical signals using compact superconducting resonators. The focus of the workshop was on strongly disordered superconductors in which it is becoming clear, theoretically and experimentally, that even in cases where the materials are “uniformly” disordered, electronic properties become inhomogeneous. The workshop brought together a cross-section of experimentalists, engineering-physicists and theorists to discuss the latest results and to identify the research-challenges ahead. The aim was to let these communities communicate and to identify problems that would be solvable and useful. Tangible outcome The relatively closed community of people interested in the complexity of strongly disordered superconductors discovered that there are communities emerging that want to use these materials in specific experiments or for detectors. A very interesting surprise of that nature was that on the first day, fresh data (one week old) were reported on quantum phase slips observed in InOx microbridges (Oleg Astafiev). A rethinking of the classification of the systems studied occurred. Traditionally separated in granular and homogeneously disordered the community became aware of the fact that the latter will also become granular on an electronic level and that a strict distinction is not intellectually productive. In anticipation of the workshop several calculations were performed to answer questions, which had come into focus because of the different communities that were coming together. Several arrangements were made to exchange samples. An in principle agreement was reached between European groups to apply for joint funding through an ITN in the Marie Curie program. Expected scientific breakthroughs It is to be expected that the ideas worked out to use these materials for quantum phase slip processes will lead to more experiments of this kind, as well as a thorough reflection on why the dissipation leading to decoherence is much lower. It is supposed to be due to the fact that the normal state is also ‘gapped’. It is expected that deviations from standard BCS electrodynamics will also be studied thoroughly. Surprising elements The power of local tunneling spectroscopy to study the properties of disordered films The usefulness of these materials in various areas of science The needed fundamental studies to make further progress in understanding and use of

these materials. Format of the workshop Despite the fact that there was ample time created for discussions that were connected to each presentation, there was a wish that more time would have been available. Almost all

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participants stayed until the last day. It was very important that we included 4 discussion sessions and asked per session to have 2 discussion leaders, giving them focused questions as a guideline. It was initially met with some skepticism by the discussion leaders, but in practice all sessions were very lively. A 2nd very important addition was an initiative by Peter Armitage to create a conference blog (http://strongdisordersuperconductors.blogspot.com/). Participants were asked to summarize talks and the discussion sessions, which was faithfully done by most. These summaries were posted and the website for the workshop of the LC referred to this site. It had two effects. The participants were actively involved in making the workshop a success by writing the piece and checking with the presenters the perceptions. In addition, while the blogspot was consulted 400 times during the workshop the blogspot continued to be used after the workshop having about 1100 hits a month later. It is the organizer’s impression that this is due to the fact that each participant, after being back in his or her own community, uses it as a resource to refer others to. Other comments Everybody was very pleased with the accommodations and the staff of the Lorentz Center. From the organizer’s point of view there is room for improvement with respect to the path from application, getting feedback from the board, as communicated in writing and explained by the staff of the Lorentz Center, rewriting the proposal and the actual experienced success of the workshop. Part of the work of the organizers is to mobilize participants for a particular format, while most of them have to pay their own costs. Intended participants have to become convinced that a workshop like this is different and special. Since we had also ICAM support it was brought to our intention that they demand application of the “Hans Frauenfelder rules for a successful workshop”. In retrospect it would have been helpful if the staff of the Lorentz Center would adopt a similar set of rules, which can be used for reference in inviting participants and setting up the program. Peter Armitage (Baltimore, USA) Mikhail Feigel’man (Moscow, Russia) Teun Klapwijk (Delft, the Netherlands)

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Baryogenesis and First Order Phase Transitions in the Early Universe

August 29 – September 9, 2011

What is the origin of the matter-antimatter asymmetry of the Universe is one of the most intriguing outstanding problems in High-Energy Physics. The Lorentz Center offered the generous opportunity to bring 39 researchers together in order to intensely discuss topics related to this fundamental question within a two week workshop. The average attendance was about 20 in the first and about 30 in the second week. The resulting seminar and lecture program was supplemented by experimental and phenomenological talks on Large Hadron Collider (LHC) physics by researchers from the Netherlands. Some particular topics presented in seminars within the field of Leptogenesis were the phenomenology of flavored models, the connection with thermal relics such as gravitinos and the formulation within the framework of non-equilibrium field theory, in particular also of resonant Leptogenesis. The non-equilibrium field theory description should be suitable in order to include radiative corrections from the thermal background, which was addressed in several presentations. The exchange on Electroweak Baryogenesis included the dynamics of the bubble wall of the first order phase transition, the production of gravitational waves from bubble wall collisions as well as particular phenomenological extensions of the Standard Model that predict a baryon asymmetry of the observed amount. Numerical simulations and analytical approximations that model preheating after inflation were another actively discussed topic. In that context falls also the model of Cold Electroweak Baryogenesis, for which different approaches for calculating the effective charge-parity violation from sources within the Standard Model were debated. The question of how to appropriately regulate infrared divergences that occur during inflation may be addressed using methods similar to those in non-equilibrium field theory, such that it found also place in the seminar and discussion program. As a more formal topic, the generation of entropy in non-equilibrium field theory was discussed. The talks on LHC physics covered top- and B-physics as well as a report on the ATLAS experiment. Besides the more formal seminar presentations, the program was supplemented by informal discussion sessions led by individual participants and that were often introduced with blackboard presentations. All of these activities were attended by most of the participants, and there were lively discussions and exchange of ideas. The goal of the workshop was to bring researchers in the field together in an era of discovery driven by the LHC and thus to initiate further progress on the understanding of the matter-antimatter asymmetry. While at the time of the workshop and up to now, no discoveries beyond the Standard Model have been made, the performance of the experiments and the many precision tests of the Standard Model are impressive. While there were a lot of interesting discussions between groups that perform research on similar topics, there was also a stimulating exchange between researchers on phenomenological models of Leptogenesis and those who are mostly working on methods and non-equilibrium theory, that has clarified a few issues. The same may be stated for the interface between thermal field theory and the theoretical description of Leptogenesis. Up to now, a number of research papers by the participants on the topics mentioned above have appeared, which were likely stimulated by the discussions at the Lorentz Center. We therefore conclude that the main goals of the workshop have been reached.

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Baryogenesis workshops by now have become regular annual events, and there is a follow-up workshop planned for Aug 2012 at the Niels Bohr Institute, organized by Anders Tranberg, one of the participants of the Lorentz Center Workshop. We would like to thank for the great hospitality and the financial and practical support offered by the Lorentz Center. In addition, we would like to acknowledge additional funding from Deutsche Forschungsgemeinschaft (DFG) and KNAW. Bjorn Garbrecht (Aachen, Germany) Tomislav Prokopec (Utrecht, the Netherlands)

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Creativity: Meaning, Mechanisms, Models

September 12 – 16, 2011 The Lorentz workshop on creativity was meant not as a mere inventory of perspectives on creativity but as a serious attempt to evaluate the meaning of the different concepts, to define the different mechanisms, and try to come to the layout of a theory that integrates the different views. The discussions were guided by the objectives that in the long run, such a theory is implemented as a computer model to validate its logical consistency and is confronted with real people to verify its empirical value. The workshop came to an integrative theory of creativity, laid down in a joint paper entitled “On the linkage between physical and organic creativity: Combinatory, complementary, emergent,” which will be submitted as a special issue to Creativity Research Journal. The center of this theory is a combinatory system that is implemented as the ACASIA program and applied in the SELEMCA-project of the national Crisp research program for the creative industries. It renders novel conceptions, one of which (the Cobra Spoon) was materialized by a gold smith. Within SELEMCA, the inner workings of ACASIA will be tested against real people. The integration of the various perspectives (i.e. physics, complexity theory, biology, psychology, design) may count as a scientific breakthrough. The ACASIA program, which is capable of suggesting novel ideas, may be the beginning of a transformation in design. The Lorentz Center Workshop on Creativity brought together thought leaders as well as students to form an interdisciplinary team of physicists, psychologists, artists, historians, industrial designers, computer scientists, and others in a week of lectures and exercises intended to generate creative breakthroughs on the questions of creativity. The participants found themselves by turns illuminated by scintillating perspectives, and frustrated by differences in belief; warmed by shared purpose, but disoriented by widely differing jargon about creativity. However, through the week’s immersive experiences which engendered trust and collaboration, the differing languages were translated, disparate perspectives were brought into closer alignment, and a holistic perspective on creativity began to emerge.

The participants considered a widely diverse set of perspectives on creativity, and a virtual menagerie of different examples of creativity, from that of the artist, to scientists like Einstein and Feynman, corporate teams of designers, to such creative natural processes as star formation and the birth of all structure in the universe. Considered also were questions of biological emergence and evolution, complexity physics as well as fractal phenomena. From the human perspective, we discussed the wonders of creativity, the psychology and the fostering of the conditions of creative thinking. We considered the physics of creativity, life and mind. We discussed the wonder that, contrary to information physics, new patterns of matter and energy (including those patterns we call life and mind) pop into existence at all. We mused about mechanisms of creativity - how diverse forms of creativity may function, and more: Whether some unifying mechanisms may interconnect these forms, which, if formulated as principles may provide a foundation of a new science of creativity – a “unified theory of creativity,” if you will.

By the end of our deliberations, we believe we identified some regularity that may underlie creativity at many different levels, from pattern emergence in fundamental physics, to the emergence of life, to the creativity of the individual and society. These results are

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preliminary, no more than a sketch, and require additional research. But the implications of an interdisciplinary science of creativity are potentially quite profound. The wider perspectives of an integrative approach may provide discoveries that no separate narrow discipline could. Each of the numerous sub-disciplines may be invigorated by fresh ideas, perturbing dogma and “well-worn ruts” that famously impede progress in established communities.

Yet, there were inevitably many issues raised that remained unanswered. For instance, if all the creative processes are indeed one, then would such a unitary principle describe the origin of life, reality, human consciousness, and human ideation? Maybe we are hard-wired to wonder where stuff comes from. Perhaps our probing minds naturally hunger to know all the secret mechanisms of our existence. Certainly creativity happens. Every single thing is new at some point in history. But where does creativity come from? Information theory says that information can be neither created nor destroyed. But patterns, irreducible and new, do emerge. Would the answer lie in complexity physics, combined with human neurobiology, evolutionary psychology, and cognitive psychology in general, guided by intuitive hypotheses about creativity? If we can unlock the principles, can we harness creativity more effectively? Can we better foster human genius? Can we apply these principles more generally and abstractly to achieve self-assembling molecular machines, or to realize machines “who” think as creatively as people do, or even more so? What about the ethics of creativity? We value creativity, and we sometimes fear it as well. Wonders happen when genius-level creativity serves humanity, but horrors result when such genius serves the psychotic dictator. What Pandora’s Box may unbridled creativity open? The format of mixing formal lectures with informal sessions such as a World Café, Appreciative Inquiry, Improv theater, speed dating, design sessions, etc. worked out wonderfully. This was the way to install trust and understanding that gave rise to an outburst of ideas and work power in the last two days of the week. This set-up is definitely recommended to groups of diverse backgrounds who wish to establish creative breakthroughs. Try to be more relaxed about different formats and deviant approaches. The time pressure by the catering firm was suffocating. Apart from that, all hail to the Lorentz Center organization team! Johan Hoorn (Amsterdam, the Netherlands) Frank Kresin (Amsterdam, the Netherlands) Arjan Postma (Amsterdam, the Netherlands)

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Challenges in Modelling the Reaction Chemistry of Interstellar Dust

September 19 – 23, 2011

The burgeoning and strongly interdisciplinary field of astrochemistry has built upon the enormous recent growth and development in our experimental, observational and theoretical efforts to understand the chemical processes occurring in the interstellar medium. Astrochemical research efforts have increasingly focussed on the role of dust grains as it has become clear that these are of crucial importance for interstellar chemical evolution. The aim of this workshop was to improve the accuracy and scope of modelling reactive processes on realistic interstellar dust grain models, specifically through identifying 1) realistic models for bare and ice-covered interstellar dust grains surfaces 2) ways of adequately dealing with quantum tunnelling and weak interactions 3) extrapolation schemes of accurate rate constants to astrochemical models 4) a concrete list of priority problems that are addressable by new collaborations. The workshop covered a broad scope of the scientific theme, through observations and experiments of ices, dust and their chemistry, theoretical calculations of these and finally long-time scale astronomical modelling. Because of this diverse exposure none of the attendees knew all participants before the workshop which has led to cross-fertilization of ideas across disciplines. Many lively discussions were observed during the informal discussion time after lunch and throughout the social events. We have asked the Chief Editor of Physical Chemistry Chemical Physics if he would be interested in a, high-profile, perspective article, covering the issues that were discussed in the workshop. He was personally looking forward to such a contribution. To this extent the organizers are currently collaborating with 3 workshop participants to put together this article covering the current state-of-the-art and a roadmap towards achieving the 4 goals stated above. During the course of the workshop it turned out that good progress has been made the last few years towards goal 1), and we have good hope that more and more accurate models will be achieved in the near future through collaborative efforts. It transpired that goal 2) was for a large part already achieved in the very recent past and that further progress can be foreseen with more powerful computers to study larger, more precise systems. The third goal can only be achieved by a closer collaboration and clearer communication across all disciplines so that the measured and calculated rate data can be translated for use in astronomical models – this workshop will contribute significantly towards that. From the discussion session at the end of each day we already have a long-list of priority problems (goal 4), which we will further delineate in the course of writing the perspective article. The format of the workshop was very accommodating towards setting up conversations across disciplines and between people that did know each other before the meeting. Especially the Wine and Cheese party on Monday opened up interactions, helped by a perfect size of the group (~50, we would certainly not recommend a bigger group, 40-50 seems ideal), and attendees coming from very many different institutions, avoiding ‘cliquing’. The lively discussion during coffee and lunch breaks, informal and formal discussion sessions always seemed to involve different combinations of people, and we therefore have to

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conclude that we have managed to achieve new links between people, which we hope to establish in long-lasting collaborations advancing this interesting, interdisciplinary field. Stefan Bromley (Barcelona, Spain) Fedor Goumans (Leiden, the Netherlands) Ben Slater (London, United Kingdom)

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Dynamics of Complex Fluid-Fluid Interfaces

September 26 – 30, 2011 The Lorentz Center workshop was a great success, with many participants commenting that they found the experience highly rewarding. Over the course of five days, 22 talks were delivered by attendants from over 12 different countries. The topics presented were roughly evenly divided between experimental characterization, theoretical methods, and simulation, but shared a common focus on modern techniques for probing, characterizing, and predicting interfacial structure and dynamics. Several of the speakers commented on the exciting overlap observed between their work and other research presented at the workshop, inspiring ideas for future collaboration. The workshop also provided a great opportunity for the 11 graduate students and post-docs present to gain exposure to more senior researchers in their field. In addition to presenting their posters to the group on Monday night, these young researchers were given the assignment of ‘interviewing’ more senior participants and coming up with several questions to address during the plenary discussion held mid-week about the most pressing challenges addressing the field of complex interfaces. Amongst the issues addressed during this plenary discussion was the difficulty of accurately probing highly elastic films at interfaces (consisting of proteins, particles, etc.), for which it is particularly difficult to find a linear response regime using current techniques. The argument was made that although techniques such as capillary pressure allow one to achieve reproducible results for a given system, it is important to distinguish between “real” and “apparent” values, particularly for measurements such as the dilatational moduli of highly viscoelastic surfaces. Discussion participants also expressed a desire for real, powerful constitutive laws for materials at an interface. Although such laws are well-developed in the field of bulk-rheology, the field of complex fluid interfaces lacks a similarly robust set of laws that can be used to model and predict interfacial structure and dynamics. Finally, some comments were made about the desirability of a few “model interfaces” which could be utilized as reference systems by all labs working in this field. These could be used, for example, to compare the interfacial properties measured using different rheological techniques. It was suggested that such models would ideally exemplify the two extremes of a purely Newtonian and purely elastic interface. While a purely Newtonian case is fairly easy to agree upon (a clean air-water interface), there is still a need for an inexpensive, highly elastic model that can be used as a standard by the community (many elastic interfaces consist of biological samples such as proteins that would be poor standards due to the variability in purification, etc.). The group was charged with brainstorming ideas for such model systems that could be used in the future. The workshop schedule also allowed time for socialization and cross-talk between participants, fostering a greater understanding of what everyone’s areas of specialization were. A number of discussions focused on potential new collaborations to address some of the big questions facing the study of interfacial structure and dynamics. At a summary meeting, participants expressed a desire to hold a follow-up meeting in the future, with a tentative goal date of September 2013. The general consensus was that such a meeting should take place in a similarly intimate working environment and with a relatively small group size of no more than 70-80 participants, in order to foster interdisciplinary collaboration and prevent the plenary discussions from becoming unwieldy. A committee of

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four persons agreed to spearhead the effort of brainstorming a specific time, location, and format for this next meeting. Dirk Bedeaux (Trondheim, Norway) Peter Fischer (Zurich, Switzerland) Signe Kjelstrup (Trondheim, Norway) Leonard Sagis (Wageningen, the Netherlands) Thijs Vlugt (Delft, the Netherlands)

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TEA-IS: Thunderstorm Effects on the Atmosphere-Ionospere System

October 10 – 14, 2011

The workshop was the kick-off of the ESF Research Networking Programme TEA-IS. The objectives of the ESF-programme are to understand the role of thunderstorms in the atmosphere-ionosphere-magnetosphere system and anthropogenic influences on thunderstorms. A holistic approach is adopted to explore a multitude of processes and their interdependencies; some processes are of such a fundamental nature that the insights gained are expected to have impacts even beyond the field of atmospheric science. The scientific topics of the programme are:

The physics of atmospheric electricity o Fundamentals of thundercloud formation and electrification o Fundamentals of atmospheric electric discharges

Lightning field-induced perturbations to the atmosphere-ionosphere o Ionisation and conductivity perturbations, and their larger scale effects o Perturbations to atmospheric chemical composition

Convection-induced perturbations to the atmosphere-ionosphere o The upper-troposphere/lower stratosphere interface o Gravity wave perturbations to the stratosphere, mesosphere, ionosphere

Applications o Technological plasma systems o The Earth’s atmosphere, weather, climate and climate change

The kick-off workshop brought the existing European community together and invited new researchers to the topics. Because of the very cross-disciplinary nature of the research subjects, one major outcome was the establishment of scientific collaboration between partners that had little prior knowledge of each other’s work. In total, eight inter-European collaborations with clearly identified objectives were identified to be carried out during the following eight months with funds of the ESF-programme. Furthermore an international summer school was prepared that will take place June 18-22, 2012 in Malaga, Spain. Elisabeth Blanc (Arpajon, France) Ute Ebert (Amsterdam, the Netherlands) Francisco Gordillo-Vazquez (Granada, Spain) Torsten Neubert (Copenhagen, Denmark)

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Physics with Industry

October 17 – 21, 2011 The second workshop Physics with Industry was organized in 2011 by the Foundation FOM and Technology Foundation STW at the Lorentz. Sixty-four scientists participated in the workshop 2011, ranging from PhD students to professors. These physicists (and researchers from related disciplines) spent a week working in groups on five industrial problems, which were selected by a programme committee from proposals put forward by industry. Following an introduction to the various problems by the companies on Monday, the participants worked on the problems in groups for the rest of the week. On the last day, the groups presented their findings to the companies. A novelty in the 2011 workshop was that some groups performed real experiments at the laboratories of Leiden University. Besides the scientific outcomes, the workshop also resulted in new public private contacts that may lead to future collaborations. Participants were mostly driven by the shear pleasure of applying their physics knowledge to new problems, the desire to enrich their scientific network and the interest in gaining hands-on experience with industrial R&D processes. Companies benefited from the scientific input they received and participating in the workshop enlarged their academic network. The five industrial problems discussed during the week were collected via an open call for proposals in spring 2011. A programme committee selected the five 'best problems' for the workshop. The selection criteria used by the committee were: it must be possible to solve the problems (or a major solution must be within reach)

within one week and physics can make a clear contribution to the solution; it should be an urgent problem; the company should be willing to share detailed information. The committee selected problems from the companies Avery Dennison, FEI Company, Nano4Imaging, Océ and Unilever. Four large companies and one SME. The proceedings are available via the FOM website. Below is a summary of the five cases. Avery Dennison: Develop self adhesive to stick on moist and icy substrates Normal acrylic-based adhesives that stick to dry surfaces, do not stick to surfaces with a water film. The water decreases the Hamaker constant, which indicates the strength of the Van der Waals forces, by a factor 10. The time needed to squeeze out the water by applying pressure to a label on top of a wet surface, is too long for normal applications. Approaches to remove, use and penetrate the moisture layer are proposed. This work focuses on proposals for water removal and this case is analyzed theoretically and tested experimentally. Pores are needed to transport the water away from the gap between the substrate and the adhesive layer. We show experimentally that adhesives with pores (50 μm diameter, 1 mm spacing) have a larger pull-off force on wet surfaces after applying pressure than adhesives without pores. Theoretical calculations for a 20μm thick adhesive layer of 645 mm2 surface area with 800 holes of 10μm diameter, show that the maximum volume of water retainable in the capillaries is 1.5 .10 -12 m3. This value is 500 times less than the volume of water squeezed out when the layer is reduced to 1μm. Therefore pores need to be made through both the adhesive and film layer where the water can evaporate or an

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absorbance layer is needed. Alternative strategies proposed to improve adhesion performance on moist icy surfaces include addition of polysaccharides, (poly)electrolytes, nanofibres, functionalized superhydrophobic and superhydrophilic patterns of the adhesive layer. FEI Electron Optics BV: Field of inserted charges during Scanning Electron Microscopy of non-conducting samples Three different approaches to calculating the electric potential in an inhomogeneous dielectric next to vacuum due to a charge distribution built up by the electron beam are investigated. An analytical solution for the electric potential cannot be found by means of the image charge method or Fourier analysis, both of which do work for a homogenous dielectric with a planar interface to vacuum. A Born approximation gives a good approach to the real electric potential in a homogenous dielectric up to a relative dielectric constant of 5. With this knowledge the electric potential of an inhomogenous dielectric is calculated. Also the electric field is calculated by means of a particle-mesh method. Some inhomogeneous dielectric configurations are calculated and their bound charges are studied. Such a method can yield accurate calculations of the electric potential and can give quantitative insight in the charging process. A capacitor model is described to estimate the potential due to the charge build up. It describes the potential build up in the first microseconds of the charging. Thereafter, it seems that more processes have to be taken into account to describe the potential well. This potential can further be used in a macroscopic approach to the collective motion of the electrons described by the Boltzmann transport equations or a derived density model, which can be a feasible alternative approximation to the more commonly used Monte-Carlo simulation of individual trajectories. Nano4Imaging BV: MRI imaging of instruments - design of markers in relation to artefact size Nano4Imaging provides magnetic markers that are fit to be put on guidewires used in MRI scanners. The size of the artefact that is induced by these markers in a MRI image depends on the geometrical and magnetic properties of the marker and the imaging parameters set on the MRI scanner such as echo time and voxel size. During the workshop we have developed a Mathematica model that predicts the size of the artefact as a function of these settings. We have demonstrated that using elementary physics, we can model an MR image for arbitrary marker properties and MRI settings. We have captured this model into a numerical simulation which produces realistic images for typical marker and MRI settings. The important MRI and marker properties are input parameters for the simulation, such that a wide variety of scenarios can be investigated. The dependency of the image appearance on the individual parameters can be understood physically. With the proposed model the artefacts generated by (super)paramagnetic markers can be simulated, without the need to use an MRI scanner. This will contribute to the rapid customization of ideally sized and shaped artefacts at low cost and rapid prototyping. Unilever R&D: Structuring with anisotropic colloids Structure is an important factor in food. One of the ways to provide structure to foods is by using bubbles and foams. However, they need to be stabilized. One way of doing this is by covering them with microscopic rods. These rods self-assemble at the surface, yielding a stable bubble. The goal of this work is to gain a better understanding into how this self-assembly works using analytical calculations, experiments and simulations.

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We have presented the results of our different approaches to the problem of self-assembly on curved surfaces. What we found, firstly, is that although some elements are present in the literature, a lot more research is needed. We have taken the first steps by looking at the analytical behaviour of the defects and the general geometry of such surfaces. In order to make the analytical calculation more realistic, one might want to add a directional energy cost for domains that fit together but have a different orientation of the rods. Furthermore, a better understanding of the exact energy cost associated with different boundaries is needed. Our experiments show that the key features of the microscopic self-assembly, such as the formation of domains, can be captured by macroscopic systems. This suggests that the main effects are geometric in nature. Our experiments we limited by the behaviour of the rods at the surface. In the microscopic case, the rods can deform the surface of the bubble and they hardly overlap. We could not reproduce this in our macroscopic systems. As a next step it would be useful to repeat the experiments with a material that can be deformed by the rods and where the rods have more buoyancy. Finally, the simulations we performed were quite successful in reproducing the general behaviour of the self-assembly, but it seems that the domains that are formed are somewhat larger than in reality. To make these simulations more realistic, one would have to change the aspect ratio of the rods, as well as the size of the bubble and the entire system (easily within reach with these methods). It would be useful to further pursue the question of polydispersity in the rod population along, as demonstrated here for DPD simulations. Although more realistic simulations would be computationally more expensive, it is still possible to do them in a reasonable amount of time within our current framework. Thus, even though this is only preliminary research, we see some promising results. Océ: Sticky bubbles We discussed the physical forces that are required to remove an air bubble immersed in a liquid from a corner. This is relevant for inkjet printing technology, as the presence of air bubbles in the channels of a printhead perturbs the jetting of droplets. A simple strategy to remove the bubble is to flush the ink past the bubble by providing a high pressure pulse. In this report we first compute the viscous drag forces that such a flow exerts on the bubble. Then, we compare this to the “sticking forces” on the bubble, due to the capillary interaction with the wall. From this we can estimate the required flow velocities for bubble removal, as a function of channel geometry, contact angle and ink properties. Finally, we investigate other ways to exert a force on a trapped bubble. In particular we focus on forces induced by electric fields which can alter the contact angle of the drop, or by locally applying thermal gradients. Once again, these forces are compared to the sticking forces to identify the parameters where the bubble can be removed. The removal of a bubble from a corner has been investigated. When the bubble is not attached to the wall, but it is near the corner, the normal flushing operation should be sufficient to remove the bubble. The flow pattern that results from the flushing was calculated. The velocity close to the corner is still significant. The drag force on the bubble has been estimated. In order to determine whether the viscous drag is sufficient to remove the bubble from the corner, the retaining force has been calculated by an analysis of the surface energy of a bubble in the corner and of a bubble in contact with a wall. For any finite contact angle, the energy of a bubble is lower in the corner, which gives rise to a retaining force. This retaining force is large enough to withstand the drag that would arise if the liquid were ejected with sonic (in air) speed from the nozzle, for a contact angle of 90. For lower contact angles, the retaining force diminishes quickly. For a perfectly wetting surface, the capillary force on the bubble is zero.

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For contact angles of 90 or more, the bubble cannot be removed by flushing. Preventing the bubble from reaching the corner becomes very important in this case. Two effects that may be used to push the bubble away from the corner were examined. The first effect is thermal migration. Three kinds of thermal influence have been considered in this report. One of them is the Marangoni effect that moves the bubble due to the dependence of the surface tension on temperature. This is the dominant contribution to the thermal migration of the bubble. The other two thermal effects are thermal convection and transfer of the vapor across the bubble due to the temperature difference at the opposite sides of the bubble. These effects are both negligible. Of these three thermal effects, only the Marangoni effect is significant. The second effect is electromigration, where an electric field induces a force on the bubble. This force is too small to overcome secondary Bjerknes force, though electrowetting may be sufficient to reduce the retaining force enough to enable flushing. Since bubbles can only be removed when the contact angle is small (hydrophyllic), controlling the wetting properties in the channel is crucial. Thermal migration may be used to prevent the bubble from reaching the corner, so that less ink is needed to flush the bubble. To use this effect, the corner must be kept cool. If these efforts prove to be insufficient, electrowetting can be investigated to enable flushing the bubble. Marcel Bartels (Utrecht, the Netherlands) Marjan Fretz (Utrecht, the Netherlands) Floor Paauw (Utrecht, the Netherlands) Pieter de Witte (Utrecht, the Netherlands)

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Error in the Sciences: Diagnosis, Prognosis, and Rectifying Measures

October 24 – 28, 2011

Goals and Themes The aim of the workshop was to explore various scientific practices of dealing with error to attain reliability as well as a deeper understanding of what error in science and its treatment entails. While the daily practice of empirical research, in and outside the laboratory, is dominated by dealing with all kinds of errors to increase the reliability of the results, there exists no general cross-disciplinary framework for addressing the problem of errors. Various sophisticated procedures for the systematic handling of observational and measurement errors, and procedures for data-analysis were and still are being developed, but they all are fragmented and mainly developed to address specific epistemological and methodological problems within a particular scientific domain. The reason that a more general account is – still – lacking is that the kind of error to be addressed differs from case to case and depends upon the effects of many different conditions peculiar to the subject under investigation, the research design, and the equipment used, and so it is context dependent and field specific. The various practices of dealing with errors have developed their own separate methods and techniques, with only little cross fertilization. While these different methods are not likely to be integrated, solutions to their common problem – how to take account of reliability – may well be. That is, while contextual knowledge is not easily transmittable to different scientific domains, methods for achieving reliability may well have over-arching features. The aim of this interdisciplinary Lorentz Center workshop was to review conceptions of error and uncertainty and to investigate possible modes of treatment by addressing the following themes: • Historical and Philosophical Perspectives on Error in Science • Error and the Method of Experimentation • Measurement Errors • Communicating Uncertainties • Social Science and Statistics The challenge of this workshop was its truly interdisciplinary nature. On the one hand we needed to explore practices of dealing with error in a specific scientific domain. On the other hand, we needed to generalize from these detailed case studies to make comparisons between the different practices. Realization To achieve the goals of the workshop we invited practitioners working in various scientific domains and disciplines as well as philosophers and historians of science, to discuss strategies of dealing with error in theory and in practice. We were successful in attracting prominent scholars from diverse domains who have been pursuing different conceptions of error and uncertainty. The invited papers were circulated in advance among the participants, using effectively the website of the Lorentz Center. Each contributor presented the gist of his or her paper in five minutes followed by an extended discussion prepared by the appointed commentator. The discussions were constructive and lively, and continued in the spirit of the Lorentz Center into the plentiful coffee, lunch, and tea breaks. The goal of fostering interaction between scientists and engineers on the one hand and philosophers, historians, and scholars in the humanities and the social sciences on the other was largely achieved. Indeed, we have allotted time for smaller groups to form and discuss specific issues at

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greater length. Of the speakers and discussants at the workshop, 10 are based in the Netherlands, 6 in the United States, 4 in Canada, 2 in the UK, 1 in Germany, 1 in Spain, 1 in Israel, and 1 in Italy. The workshop attracted 35 registered participants in a truly international spirit. The idea that each day should be dedicated to one theme, to be addressed from different perspectives, proved most productive. To orient and focus the discussion we started each day with a programmatic introduction to remind participants of the research questions posed in the workshop description. There was one public lecture delivered by Professor Maarten Hajer, “Communicating scientific results to lay audience, facts or uncertainties (the case of climate change)”. Both the interdisciplinary nature of the discussion and its concrete focus were accomplished to such a degree to consider the week-long workshop a success. One of the contributors reflected on his experience at the workshop: “Congratulations for the successful choice of people from different disciplines and creating the right atmosphere for constructive and informative discussions. I thoroughly enjoyed our discussions and I will do my best to help with any subsequent phase of that initiative.” Another contributor commented in writing: “It was an honor to be included among the participants. I can only hope that my contributions were in some way helpful to the other participants. I certainly benefited greatly from the contributions of others. As I mentioned at the close of the meeting, the workshop will go into my ‘personal pantheon’ of those very few meetings that have really changed how I think about some of the things I am working on.” The workshop organizers are grateful to the Lorentz Center team that supported this workshop, Mieke Schutte, Henriette Jensenius, and Sietske Kroon. Lastly, we are grateful to all the financial sponsors of the Lorentz Center and the NIAS that made it possible to organize this workshop. Marcel Boumans (Amsterdam, the Netherlands Giora Hon (Haifa, Israel) Arthur Petersen (Amsterdam, the Netherlands)

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Tipping Points in Complex Flows – Numerical Methods for Bifurcation Analysis

of Large-Scale Systems

October 31 – November 4, 2011 In this workshop a mix of scientists who are at the forefront of developing new methods, users of these methods in a diverse range of applications and new potential (in particular, young) users of these methods gathered to discuss the state-of-the art of Numerical Methods for Bifurcation Analysis of Large-Scale Systems. The number of participants varied during the week around twenty. The specific aims of this workshop were (i) to assess the state-of-the art of the methodology, (ii) to assess the remaining challenges and remaining numerical difficulties, (iii) to develop a road map for future research, and (iv) to foster cooperation in research as well as in training of students. The outcome of the workshop are as follows: 1. The participants agreed to prepare a review paper on the subject. 2. Two challenging test problems were posed that will be made known in the field. Comparison of results is envisaged at the BIFD conference in Israel in summer 2013. 3. For new researchers in the field (MSc and PhD-students) a set of introductory problems will be made available through the website of the SIAM activity group on dynamical systems. Comparing this to our aims we consider this as a very successful workshop. The program format was focused around the setup of the review paper, from which an outline was showed during the welcome, and was presented as a possible outcome of the workshop. We followed the following daily schedule. In the morning there were 2 lectures of about 1 hour and 1 hour of discussion, and in the afternoon 1 lecture and again one hour of discussion. For Monday the intention was to gather elements for the introduction of the paper. So the speakers were from application areas and discussions concentrated on challenging problems, the added value of bifurcation analysis and selling points. On Tuesday and Wednesday we focused on methodology. So the subjects of the speakers ranged from algorithms for bifurcation analysis to enabling techniques from numerical linear algebra. Next to these techniques we tried to get clear the state-of-the art in the discussions. More specific a list was made of what kind of bifurcations can be solved today with current available techniques/software. The Thursday talks were on uncertainty in dynamical systems. This is rather new in this field and therefore no special discussion time was allotted for this. In view of earlier leaving participants we discussed a zero version of a review paper which was prepared by one of the organizers during the workshop. Also authors were indicated in the text. At this point all the proposed authors committed to do their part. All other participants were invited to send a few pages on a specific problem they solved (indicating clearly the techniques and effort

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needed to solve it). Furthermore, in this discussion we came to the outcomes 2 and 3 mentioned above. On Friday there were two talks on very challenging problems, one of which grew out to a test problem we want to set to the entire community. Since the outcomes made this workshop to a success we advocate this approach to future organizers. For a list of speakers, abstracts and presentations we refer to the website of the workshop. In order to stimulate cohesion and fruitful discussions, we started after the first lecture with a round-table discussion in which each participant told about his/her relation to the subject. This helped tremendously to get the plenary discussion going. Furthermore, there was ample time in the program for bilateral discussions. Also the focusing on a review paper stimulated cohesion. Many of the participants were impressed by what can be done by state-of-the art techniques and this observably led to intense discussions on approaches. On Wednesday afternoon there was a guided walking tour through the historic city of Leiden. Half of the participants took part in that and were enthusiastic. After the tour the workshop dinner took place in the city in which all participants took part and which was very lively. Henk Dijkstra (Utrecht, the Netherlands) Fred Wubs (Groningen, the Netherlands)

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Uncertainty Analysis in Geophysical Inverse Problems

November 7 – 11, 2011 Aims and Scope Our workshop was motivated by recent advances in computer science and applied mathematics that enabled us to start solving realistic large-scale inverse problems in the Earth sciences, including weather and climate forecasting, imaging the Earth’s internal structure, predicting ocean currents, and estimating flow patterns in the Earth’s mantle and outer core. The finite amount of data, the presence of noise and incomplete forward models introduce uncertainties in the solution of inverse problems that are often not properly quantified, despite their undisputed social and economic relevance, for instance in the context of geophysical exploration or the prediction of extreme local weather conditions. Significant progress in uncertainty analysis can be made by realising that most inverse problems are very similar on an abstract mathematical level, and by fostering the communication between applied mathematics and various geophysical disciplines that use different approaches. The principal objective of the workshop was thus to provide a communication platform for mathematicians, seismologists, meteorologists, oceanographers and geodynamicists that promotes the transfer of methodologies across the disciplines and the homogenisation of the diverse scientific vocabularies. Tangible outcomes The most concrete outcome for all participants was the recognition that inverse problems across the geosciences are indeed similar to a degree that allows for an easy transfer of methodologies and concepts. For instance, a sampling strategy for high-dimensional probability densities mostly used in solid-Earth geophysics (the so-called Neighbourhood algorithm) was found to be applicable in data assimilation applications such as weather forecasting. We furthermore recognized how to translate inverse problem formulations typically used in meteorology and oceanography to seismic tomography, thereby opening entirely new perspectives for uncertainty analysis in tomographic applications. Our workshop was marked by a continuous learning process that started with major problems understanding each other and ended with an increased interest and ability to communicate across the disciplines. The establishment of many new research connections is probably the most important outcome of our workshop. With the help of our newly developed common language, we were able to formulate a list of key problems that we think our communities should address and solve in the new future. Our plan is to assess our progress in a second workshop that should take place in 2 to 3 years. Finally, the discussions of our workshop will be summarised in a review paper entitled Uncertainty Analysis in Geophysical Inverse Problems, that we hope to publish in Annual Reviews of Earth and Planetary Sciences. Organisation and Format The participants generally appreciated the informal organisation and very much enjoyed the academic atmosphere at the Lorentz Center. The format was ideal for what we wanted to achieve. We quickly developed a culture of vivid discussions that lasted throughout the week. We often used the allocated discussion time during the talks already, continued during the coffee and lunch breaks and indeed dinner time. The visibility of the posters from Monday to Friday was very helpful, especially for the students who used the opportunity to establish connections with the more senior scientists.

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A key element of our workshop was the daily morning lecture that introduced one specific field, e.g. seismic tomography. The lectures completely fulfilled their purpose of enabling a very diverse audience to engage in discussions In summary, our workshop was a great success, and it was a pleasure for everybody to enjoy science at the Lorentz Center. Andreas Fichtner (Utrecht, the Netherlands) Peter Jan van Leeuwen (Reading, United Kingdom) Jeannot Trampert (Utrecht, the Netherlands)

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Land for Bioenergy: Ecological, Economic and Societal Aspects

November 14 – 17, 2011

Workshop description, aims and outcomes A number of global policies have been put in place to meet CO2 emission reduction targets, among them an increase in energy produced from crops, such as corn, sugar cane, palm oil or jatropha. Implementation of those policies, however, will take place on a regional, or even local scale. Thus, in order to achieve a sustainable increase in biofuel, concrete policy considerations for regional bioenergy deployment are necessary. Aim of the workshop was thus to investigate potential local to global benefits, implications, and constraints of pursuing expanded bioenergy production on biodiversity, ecosystem services and socio-economic systems, and to develop interdisciplinary, cross-cutting approaches to address the question. Twenty-six participants from seven countries, including Brazil, Argentina and South Africa, attended the workshop to develop an overarching framework to guide sustainable bioenergy production in different regions across the globe. The group assembled for the workshop was rather unique, enabling it to provide a combine perspective of global and regional interdisciplinary approaches (in developed and developing countries), and uniting socio-economic, biodiversity and ecosystem services and agriculture and forestry perspectives. This provided an excellent opportunity to gain new insights into already existing questions, develop new angles of consideration of the problem, and for learning from each other. Especially the interactions between the socio-economic and ecological community were very fruitful, as these two scientific communities rarely cross paths, but are required to work much closer together in the future to tackle society's problems in a rapidly changing world. At the end of the workshop, the group had developed an outline for a review paper that will draw on previous experiences (presented as regional case studies) to identify the potential local to global benefits, implications and constraints of pursuing expanded bioenergy crop production, and to develop policy considerations for regional bioenergy deployment. It is envisaged to submit the paper ahead of the Rio+20 Summit in 2012. Workshop organisation/format The workshop was organized in different sessions, each dedicated to a different aspect of the workshop. The sessions were introduced by short plenary talks, and the group then invited to discuss the topic at hand. As we were a fairly small group, the discussions were also held in plenary, thus facilitating the interaction and exchange between disciplines, and encouraging the sharing of regional experiences. The relaxed atmosphere at the Lorentz Center, as well as the provision of small offices, and the availability of white boards almost everywhere also were very conducive to fostering discussion and exchanges, and participants made actively use of this. At the end of the workshop, new collaborations had formed, and participants were grateful for the opportunity to broaden their horizon. All participants were impressed with the facilities and services the Lorentz Center provided, and also enjoyed the social functions, especially the boat cruise dinner, very much. We

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would like to thank the Lorentz Center not only for funding the workshop, but also for the logistic support they, and especially Gerda Filippo, provided. Ada Ignaciuk (Paris, France) Cornelia Krug (Paris, France) Rik Leemans (Wageningen, the Netherlands) Jasper van Vliet (Bilthoven, the Netherlands)

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Towards a Consensus Model of Yeast Glycolysis

November 20 – 25, 2011 In biology, the use of mathematical models is rapidly increasing to allow scientists to interpret data, generate hypotheses, discriminate between mechanistic explanations, and, ultimately, predict the outcome of perturbations as applied in biotechnology and (bio)medicine. Making a detailed kinetic model of a part of a biological system is challenging, for many reasons. Most regulatory interactions are highly non-linear and often supported by error-prone datasets. From the early days that computers were used in biology, the glycolytic pathway has been a prime subject to kinetic modelling, and in particular glycolysis in the yeast Saccharomyces cerevisiae. In the research community, many groups are working on different updates or versions of a yeast glycolysis model, using only parts of the plethora of data available. This fragmented situation is reminiscent of that of genome-scale stoichiometric models a few years ago. In the latter cases, the confusion was settled by a jamboree where the involved scientists sat together and agreed upon a consensus model, including the necessary annotations. In this workshop, we have brought together the people actively working on yeast glycolysis, both experimentally and computationally, with the aim to share data, models and knowledge to come to a consensus, maximally validated, kinetic model of yeast glycolysis. During the workshop we have had mostly breakout session and discussion groups to work on topics that we identified in each of the morning sessions. The main issues were (i) data management; (ii) enzyme kinetics and data; (iii) parameter estimation pipeline development; (iv) method development for the boundaries of the model. A number of lectures that highlighted the potential applications of the model were scheduled in the afternoon, including talks on industrial applications, and relevant processes that we will not directly address in our models, such as signalling and ion homeostasis. The staff of the Lorentz Center characterized the spirit well: “wow, this is really a workshop!”. We have used the week in Leiden to really develop a workflow for this project, and made the first steps to implement it. (i) Data management: templates and workflows have been developed to be able to really integrate data sets. Issues related to metadata, strains, conditions, conversion factors etc have been resolved in a continuous discussion between experimentalists and modellers. (ii) Enzyme kinetics: we have discussed possible kinetic formats, data availability and way to reach consensus. Subsequently we have developed fact sheets with all state-of-the-art knowledge for every step in the glycolytic pathway. (iii) Parameter estimation: a three-step process is developed and will be tested as soon as all the data is available (iv) Boundaries: for a number of important interactions between glycolysis and the rest of metabolism we have discussed and developed a strategy on a case-by-case basis We feel the workshop was a big success, we created considerable momentum and trust amongst the researchers in the field, we developed workflows and distributed the work between the groups. Also after the workshop has ended, we continued to add data to the database. The success of the workshop is also reflected by the award of the NCSB stimulus grant of the Netherlands Consortium for Systems Biology, Jan 2012. This grant allows us to hire dedicted postdocs to carry out the workflow within the next two years. Without the

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great help of the Lorentz Center, this would not have been possible, and we thank Sietske Kroon and Mieke Schutte for their help. Matthias Heinemann (Groningen, the Netherlands) Joerg Stelling (Basel, Switzerland) Bas Teusink (Amsterdam, the Netherlands)

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Mathematics: Algorithms and Proofs

November 28 – December 2, 2011 The main goal of the workshop was to ‘achieve a fruitful interaction between the implementors of computer mathematics, both verified and unverified, and core mathematicians and logicians.’ This goal was certainly achieved, the workshop was very lively and stimulating to many participants. Moreover, the meeting was a good venue for the ForMath project to gather and to present their work to a wider audience. With 55 registered participants and 5 to 10 unregistered participants coming in for a couple of days, this was the biggest MAP-meeting since to workshop series was started in 2003. Abstracts and slides of most of the presentations are available from the workshop webpage. The presentations can roughly be divided in three groups. Computational and constructive mathematics: This includes the two tutorials, by Barakat and Quadrat and by Simpson and Escardo, and the presentations by Avigad, Bauer, Griffin, Mannaa, van der Vorst, Yengui. This kind of work is either an application of the methodologies developed within MAP, or a direction in which we envision that these methodologies will be useful. Formal proofs: Cohen, Gonthier, Rubio and Théry presented the state of the art in formalizing mathematics in type theory. In all presentations it was essential to have a good overview of the mathematics before formalizing it. In Rubio's case the computer verification of software for algebraic topology lead to the correction of a mathematical result. Homotopy type theory: The developing field of homotopy type theory, a marriage between abstract homotopy theory, type theory and higher dimensional category theory, was a very stimulating meeting point for many participants. There were lectures on this topic by Awodey, Harper, Hyland, Kapulkin, Moerdijk and Streicher. It was a great pleasure to be welcomed in the Lorentz center. Especially, the availability of offices was greatly appreciated by many participants. We would like to heartily thank its very efficient and helpful staff. Thierry Coquand (Göteborg, Sweden) Henri Lombardi (Franche-Comte, France) Marie-Francoise Roy (Rennes, France) Bas Spitters (Nijmegen, the Netherlands)

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Isotopes in Astrochemistry: an Interstellar Heritage for Solar System Materials?

December 5 – 9, 2011

Scientific Case and Motivation The matter comprising the Sun and the planets, as well as the comets and asteroids, originated in the dense core of an interstellar cloud over 4.6 billion years ago. The aim of the workshop was to obtain a clearer picture of the fate of observed interstellar isotopic fractionation patterns as they were incorporated into the protosolar nebula. A major goal was to ascertain which of the molecular isotopic signatures found in primitive Solar System materials are indicative of pristine interstellar or circumstellar matter and if it has survived stellar evolution and planetary formation. The primary focus was on the volatile elements (D, C, N, and O) in the following disciplines: (1) the contribution of stellar nucleosynthesis to Galactic chemical evolution, (2) observed isotopic fractionation in interstellar clouds and protoplanetary disks, (3) isotopes in comets, (4) isotopic anomalies in meteorites and IDPs (including the Stardust samples), (5) and new results from Herschel and ALMA. The Workshop The workshop was represented by 53 scientists from 10 different countries to present the state-of-the-art knowledge in their respective areas of expertise, and also provide a forum for younger scientists wishing to become acquainted with isotopes in Astrochemistry (9 registered postdocs and students, and numerous local participants). We started the week with a big picture overview and introduction to isotopes, the major questions, and background of the different topics to be discussed throughout the week. The workshop was divided by major disciplines (listed above), which included at least one review presentation, contributed talks, and at least one panel discussion. Each panel discussion was lead by experts and stimulated detailed, and lively, discussion by participants from all fields. These conversations often carried over into the breaks, lunch, and even at the hotel after the meeting each day. Multiple participants were often found in the private offices debating over current issues and new data presented. This very interdisciplinary workshop, with a key science goal, was highly successful and promoted new insights for every field. The participants seemed inspired and some have found new collaborations in other disciplines for observing proposals, visiting speakers, sharing data sets, and advisement. Many of them also commented on the highly successful meeting including organization by the Lorentz Center and its staff, the scientific quality and interdisciplinary nature of the workshop, and look forward to future meetings on this topic. We would like to thank the Lorentz Center, NOVA, the Goddard Center for Astrobiology, and the Leiden Observatory for financial support. Conel Alexander (Washington DC, USA) Steven Charnley (Greenbelt, USA) Ewine van Dishoeck (Leiden, the Netherlands) Stefanie Milam (Greenbelt, USA)

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Modeling and Observing Dense Stellar Systems

December 12 – 16, 2011 Motivation The formation and evolution of dense stellar systems are driven by a wide variety of tightly coupled physical phenomena. Understanding these phenomena requires similarly close coordination among experts in the field – astronomers, physicists, and computer scientists with observational and theoretical expertise in galactic and extragalactic astronomy, stellar and galactic dynamics, fluid dynamics, stellar evolution, and the development of high-performance hardware and software. The overarching goals of this workshop were to foster long-term collaborations among observers and modelers working in related fields, to define new joint projects likely to advance these collaborations, and create a modeling framework within which realistic simulations of dense stellar systems can be carried out and compared with reality. Participants The workshop was attended by around 35 national and international scientists with varying backgrounds. The group consisted of leading senior and junior researchers as well as PhD students and Master students, from the theoretical and the observing community. Program The main program consisted of short talks in the morning, with lively discussions in between and break-out and work sessions in the afternoon. During the workshop extra, ad-hoc, sessions were organized for PhD students and young researchers to present their work. Each short (10 minutes) presentation was followed by a discussion of about 20 minutes. A tutorial and some work sessions were focused on AMUSE, a scientific software package being developed in Leiden and incorporating many of the ideas discussed during the workshop. Every day of the workshop was focused around a central theme: 1. Critical observations of star clusters 2. Key modeling challenges in dense stellar systems 3. Planets and proto-planetary systems 4. High-performance multi-physics simulations 5. Stars as the fundamental building blocks of stellar clusters Impressions The talks showed the forefront of theoretical and observable knowledge in dense stellar systems. After each talk, many key points were discussed in depth and the interaction between researchers of different fields was high. A rough model of star cluster formation emerged, based on hierarchical models (from clumps of stars merging into clusterings and these merging into larger systems). This model may be supported by observations in active star forming regions in the Large Magellanic Cloud. Further theoretical modeling was discussed and some plans were made for future work and collaboration. Another interesting discussion focussed around stellar and especially binary stellar evolution inside dense stellar systems. Several modelling challenges (different dynamical time scales, stellar evolution models, escaping binaries from clusters) were discussed as well comparing these to observable data. Finally we want to highlight the many discussions on modeling these dense systems that have many different physical phenomena and also multiple time and distance scales. AMUSE

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was presented as a computer tool to help with modeling these systems and several researchers showed interested in using it for future work and even extending it with their personal codes. A number of arrangements were made for future collaborations. Acknowledgement The workshop organizers are very grateful to the Lorentz Center team that supported this workshop. Their skill and professionalism showed during all phases of the workshop organisation. As scientific organisers organizing the workshop was a "breeze". Arjen van Elteren (Leiden, the Netherlands) Piet Hut (Princeton, United States) Steve McMillan (Philadelphia, USA) Inti Pelupessy (Leiden, the Netherlands) Simon Portegies Zwart (Leiden, the Netherlands) Marco Spaans (Groningen, the Netherlands)

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MAO –Multi-Agent Organisation

December 19 – 23, 2011 Multi-Agent Systems is a computational paradigm for modelling intelligent distributed systems. A major challenge in the design and development of multi-agent systems is the regulation and coordination of the behaviors of individual autonomous agents in order to guarantee the achievement of the overall objectives of open multi-agent systems. Recognized solutions for this challenge advocate the use of normative and organizational concepts. The aim of this workshop was to promote the discussion and exchange of ideas concerning computational models and programming frameworks for the design and development of normative multi-agent system organizations. In particular, our aim was to identify the key shared concepts, models, tools, and techniques based on which a uniform and coherent framework for normative multi-agent organizations can be defined. The workshop was divided into morning and afternoon sessions. For the morning sessions, we had invited 18 experts on various aspects on normative systems and multi-agent systems. For the afternoon sessions we formed three discussion groups with the themes ‘conceptual analysis of normative multi-agent systems’, ‘logical analysis of normative multi-agent systems’, and ‘computational analysis of normative multi-agent systems’. These working groups discussed these themes in separate rooms during the first afternoon sessions. The second afternoon sessions were plenary sessions in which the summary of discussions from various groups were presented and discussed. The outcome of the workshop will be summarized in a manifesto in order to frame the main issues in computational normative multi-agent organizations and to sketch a roadmap identifying the research agenda. The results of the afternoon sessions form the basis for the roadmap. This document provides an overview of the state of art in multi-agent organizations in terms of the key shared concepts, models, theories, technologies, and tools that support the design and development of programming languages for normative multi-agent organizations. The manifesto also provides an overview of the current trends and the challenges that should be met in the next couple of years. • Conceptual analysis: After four days of intensive discussion, agreement was found on a

common framework. • Logical analysis: Two traditional analyses were identified, based on normative systems

and deontic logic on the one hand, and game theory on the other hand. The dynamics of the assignment of roles to agents and the corresponding powers of the agents was identified as a main subject of further study.

• Computational analysis: A bridge was made between methods used in software engineering, such as Paradigm and Reo, and the methods currently under development in the area of normative multiagent systems, such as 2OPL and MOISE.

The manifesto will be presented during the NorMAS seminar that will take place in Dagstuhl in March 2012, and we plan to use this manifesto as a starting point for a joint publication in an international conference such as AAMAS or related journals. We would like to thank the Lorentz Center for giving us the opportunity to organise this workshop. The participants were very enthusiastic and positive about the Lorentz Center and how the workshop was organized. They found the workshop very interesting and productive.

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Mehdi Dastani (Utrecht, the Netherlands) Guido Governatori (Queensland, Australia) John-Jules Meyer (Utrecht, the Netherlands) Leendert van der Torre (Luxembourg, Luxembourg)

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FUNDING SOURCES OF THE LORENTZ CENTER Basic Funding of the Lorentz Center Funding granted to the Lorentz Center, supporting its operational activities and providing a budget to each meeting held at the Lorentz Center

Leiden University Faculty of Science at Leiden University

Facilities and staff

FOM Foundation for Fundamental Research on Matter

Workshops in Physics

NWO Netherlands Organisation for Scientific Research

Workshops in Astronomy, Computational Sciences, Informatics, Life Sciences, Mathematics, and workshops within the NIAS-Lorentz Collaboration

OCW Ministry of Education, Culture and Science

Workshops in Astronomy, Computational Sciences, Informatics, Life Sciences, Mathematics, and workshops within the NIAS-Lorentz Collaboration

NIAS

Workshops within the NIAS-Lorentz Collaboration

Lorentz Fonds

Workshops in Physics

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Additional Funding for specific Lorentz Center Meetings Funding granted to scientific organizers of meetings held at the Lorentz Center

Sponsor

Workshops

Abbott Molecular

Circulating Tumor Cell Isolation and Diagnostics

Anton Paar


Applied Rheology


ASTRON


Avery Dennison


BioSolar Cells

Modeling Natural and Artificial Photosynthesis

Brandeis

Fluctuations and Response in Active Materials

Catholic University of Leuven

Advanced Magnetohydrodynamics

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85

Cecam

> Control of Burning Plasmas > Advanced Magnetohydrodynamics > Modeling Natural and Artificial Photosynthesis > Multiscale Fluid Dynamics with the Lattice Boltzmann Method

CNES


COST

> Analysis and Visualization of Moving Objects > Challenges in Modelling the Reaction Chemistry of Interstellar Dust > MAO – Multi-Agent Organisation

Crisp


CWI


TU Delft


DFG

Baryogenesis and First Order Phase Transitions in the Early Universe

DIAMANT Cluster


DIVERSITAS

Land for Bioenergy: Ecological, Economical and Societal Aspects

DLR


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DSM


ESA


ESF European Science Foundation

Thunderstorm Effects on the Atmosphere-Ionosphere System

ESSP Earth System Science Partnership

Land for Bioenergy: Ecological, Economical and Societal Aspects

Europlanet


TU Eindhoven


FDL TU Eindhoven

Multiscale Fluid Dynamics with the Lattice Boltzmann Method

FEI


FOM Institute for Plasma Physics Rijnhuizen

> Control of Burning Plasma > Advanced Magnetohydrodynamics

Foundation Compositio Mathematica

> 4th European Women in Mathematics Summer School > The Motivic Fundamental Group > Mathematics: Algorithms and Proofs

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87

FreedomLab VU Future Studies


Friesland Campina


FWO-WOG


GCA

Isotopes in Astrochemistry

GQT


ICAM


ILLC


IMAU

Tipping Points in Complex Flows

ING Amsterdam


J.M. Burgercentrum

> Physics of Mixing > Multiscale Fluid Dynamics with the Lattice Boltzmann Method

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88

Janssen


Johann Bernoulli Institute


Johnson-Johnson


Kavli Foundation


Kavli Institute of Nanoscience


KBC Bank Brussel


KdVI


KNAW

> Cosmic Ray Interactions > 4th European Women in Mathematics Summer School > Discrete Integrable Systems Challenges in Modelling the Reaction Chemistry of Interstellar Dust

Leiden University Honours Program

Modeling Natural and Artificial Photosynthesis

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Leiden University Leiden Observatory

> Multiscale Fluid Dynamics with the Lattice Boltzmann Method > Circulating Tumor Cell Isolation and Diagnostics

Leids Universiteits Fonds

Beam Shifts: Analogies between Light and Matter Waves

London Mathematical Society


Marie Curie Actions

> Quantum to Classical Crossover in Mechanical Systems > Uncertainty Analysis in Geophysical Inverse Problems

MIRA


MNN


Molecular Logic Circuits

Molecular Logic

Nano4Imaging


NDNS+ Cluster

> Coherent Structures in Dynamical Systems > Discrete Integrable Systems > Tipping Points in Complex Flows

NISB


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90

NOVA

> Probing the Radio Continuum Universe with SKA Pathfinders > Cosmic Ray Interactions Herschel and the Characteristics of Dust in Galaxies > Workweek: Towards Understanding Imaging Data from LOFAR

NSF


NWO (additional)

> 4th European Women in Mathematics Summer School > Mathematics: Algorithms and Proofs

NWO ERGO

Transgenes Going Wild

Océ


PBL

Error in the Sciences: Diagnosis, Prognosis and Rectifying Measures

Philips


PICNIC


Quest

Uncertainty Analysis in Geophysical Inverse Problems

90

91

Rabobank Utrecht


RadioNet

> Probing the Radio Continuum Universe with SKA Pathfinders > Workweek: Towards Understanding Imaging Data from LOFAR

Radboud University Nijmegen


Wageningen University


SIKS

MAO – Multi-Agent Organisation

SINTERFACE Technologies


SKA


7th Framework Programme

Quantum to Classical Crossover in Mechanical Systems

SRON

> Cosmic Ray Interactions > Herschel and the Characteristics of Dust in Galaxies

STAR Cluster

Extreme Value Statistics in Mathematics, Physics and Beyond

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92

Stichting Physica

Cosmic Ray Interactions

TA Instruments


Technex bv


TECLIS


The Thomas Young Center

Challenges in Modelling the Reaction Chemistry of Interstellar Dust

Thomas Stieltjes Institute for Mathematics


TNO


UNICELLSYS


Unilever


University of Amsterdam

100th Anniversary of Superconductivity: Hot Topics and Future Directions

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University of Amsterdam Swammerdam Institute


University Amsterdam VU Camera


University of Groningen

Tipping Points in Complex Flows

University of Utecht

> Landing Sites for Exploration Missions > Advanced Magnetohydrodynamics

University of Utrecht Mathematical Institute


Vereniging voor Logica


Veridex LLC


Waag Society


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