Major Issues in Nuclear Physics Aided by Massive Computation

transcript

Forefront Questions in Nuclear Science and the Role of High Performance Computing

January 26-28, 2009 · Washington D.C.

David B. Kaplan ~ Institute for Nuclear Theory

The challenge of nuclear theory

• Many-body problem of interaction nucleons• Quantum mechanical• Strongly interacting

pre- 1970s ~ phenomenological models:

Predictive phenomenology; qualitative theoretical understanding

The challenge of nuclear theory

• Many-body problem of interaction nucleons• Quantum mechanical• Strongly interacting

pre- 1970s ~ phenomenological models:

Predictive phenomenology; qualitative theoretical understanding

• A simply expressed, complete theory of the strong interactions• Nucleons are bound state of quarks & gluons• Quantum mechanical• Strongly interacting• Relativistic

post-1970s ~ Quantum Chromodynamics (QCD):

1980’s, 1990’s: a ferment of ideas

Exchange of ideas with particle theory:• Effective field theory• String theory• Symmetries

Experiments:• Precision symmetry tests• SN 1987A• Neutrino masses• RHIC, JLab• Trapped atoms...

Exchange of ideas withcondensed matter & atomic theory:• Quantum chaos• Density functional theory• Color superconductivity of quark matter

5th ANL/MSU/JINA/INT FRIB Workshop: Bulk Nuclear Properties Nov. 19 - 22, 2008

Workshop on Relativistic Dynamics of Graphene Jan. 8 - 11, 2008

Nuclear Interactions at Ultra-high Energy in Light of Recent Results from Auger Feb. 20 - 22, 2008

From Strings to Things: String Theory Methods in QCD and Hadron Physics March 24 - June 6, 2008

Soft Photons and Light NucleiJune 16-20, 2008

The QCD Critical PointJuly 28 - Aug. 22, 2008

Low Energy Precision Electroweak Physics in the LHC EraSept. 22 - Dec. 5, 2008

Atomic, Chemical, and Nuclear Developments in Coupled Cluster Methods June 23-July 25, 2008

The diversity of nuclear theory: INT programs 2008

2000’s: Computational nuclear physics comes of age

• Lattice QCD• Advances in the shell model• Density functional methods• Coupled cluster techniques...

Experience from TFlops-years: a glimpse of a unified nuclear theory grounded in QCD, aided by extreme computing

Structure: from quarks and gluons to heavy nuclei

Dynamics: evolution of the quark gluon plasma in a heavy ion collision; fusion and fission processes which power stars and create elements; the cataclysmic explosions of stars

Origins

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The extreme computing opportunities and challenges for nuclear physics all come together in describing the life of a star

Origins

Nucleons, resonances

Quark-gluon plasma

Matter/anti-matter annihilation

Exascale challenges:

QCD phase diagram

Structure of the nucleon & resonances

Clues about origin of matter/anti-matter asymmetry

Origins

Phase diagrams: Water...

...primarily explored in the laboratory

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Phase diagrams: QCD (an educated guess!)...

...to be explored by accelerator, telescope & computer

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Observation

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Observation

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Experiment &EXASCALE

Computation

Observation

EXASCALE Computation

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Experiment &EXASCALE

Computation

Origins

Recreating the Big Bang in heavy ion collisions

Experimental program: RHIC, LHCTheory challenge: a unified description of a heavy ion collisions

Origins

Initial conditions: quark/gluon distribution in ions

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Thermalization; quark-gluon plasma

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Expansion and hadronization

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Relativistic hydrodynamics

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Departure from thermal equilibrium

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Predicting observables

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• Important physics• Ambitious computation

EXASCALE?

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• Important physics• Ambitious computation

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Quark & gluon structure of nucleons and resonancesfrom lattice QCD

Experimental program: JLabTheory challenges:

Origins

• What is the momentum distribution of quarks and gluons within the nucleon?

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Structure functions, strange quark content

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• How do currents couple to the nucleon?

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• How do currents couple to the nucleon? High precision form factors (gA to <1%?)

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• How do currents couple to the nucleon? High precision form factors (gA to <1%?)

• Predict exotic states (glueballs, hybrid mesons)

Big Bang:Why is there more matter than anti-matter today?

A key ingredient: violation of baryon number or lepton number symmetryOrigins

Neutrino-less double beta decay = lepton violation

• Subject of intense experimental search • Requires calculation of nuclear matrix

element

Experimental program: Majorana, Cuore, EXO, NEMO3...Theory challenges:

A key ingredient: violation of baryon number or lepton number symmetry

The structure of 76Ge, 150Nd and calculation of relevant matrix element is an Exascale problem

EXASCALE

Origins

Neutrino-less double beta decay = lepton violation

• Subject of intense experimental search • Requires calculation of nuclear matrix

element

Experimental program: Majorana, Cuore, EXO, NEMO3...Theory challenges:

Extreme computing: the era for understanding and predicting nuclear reaction rates

Solar fusion:Exascale era: solar fusion rates can be obtained directly from QCD

Fusion

Technique: “Lattice QCD”• Quarks & gluons interacting on a

spacetime lattice.

• Highly parallelizable.

Fusion

spacetime lattice.

• High precision nucleon form factors (e.g. gA to <1%?)

• High precision 2-body forces• Calculation of 3- and 4-body forces

directly from QCDeg: energy levels of four neutrons in a box: not accessible experimentally

Fusion

spacetime lattice.

EXASCALE

• High precision nucleon form factors (e.g. gA to <1%?)

• High precision 2-body forces• Calculation of 3- and 4-body forces

directly from QCDeg: energy levels of four neutrons in a box: not accessible experimentally

Fusion

Metals

3- and 4-nucleon interactions from lattice QCD

Ab initio nuclear structure & reaction calculations

• GFMC• No-core shell model...

The output from one class of extreme computations feeds into the next:

EXASCALE

Metals

Triple alpha process

Alpha capture on p-shell nuclei

Metals

Alpha capture on p-shell nuclei

EXASCALE

Metals

Super-nova

Cataclysmic events in the heavens

Type I SN: thermonuclear explosion; key distance marker for astronomers

Type II SN: core collapse; origin of heavy elements, neutron stars. Neutrinos play a leading role.

X-ray bursters, colliding neutron stars...

Super-nova

EXASCALE nuclear astrophysics:

• Realistic 3D simulations of core-collapse SN; expect to uncover robust explosion mechanism

• 3D simulations of Type I SN including turbulence effects

• Pulsar & magnetar simulations

Super-nova

Type II Supernovae are the site for synthesis of heavy elements (“r-process”)

Super-nova

Density functional theory:• Compute shell structure along r-process path• Compute shell structure around 100Sn• Provide microphysical theory of fission

Super-nova

FRIB:• Experimental studies of

neutron-rich isotopes

Super-nova

Supernova simulations:• Predict element

abundances• Predict terrestrial

neutrino flux

Super-nova

Supernova simulations:• Predict element

abundances• Predict terrestrial

neutrino flux

EXASCALE

Super-nova

Dynamics from density functional theory:

• Evolution of fissioning nuclei from a microphysical Hamiltonian

• Prediction for distribution of fission products

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One of the biggest challenges: extended matter at nuclear densities and higher, from QCDCollapse

Present approaches: nuclear matter from QCD is an exponentially hard problem...NOT Exascale-ready

EXASCALE

However: an important piece of the problem can be addressed

Exotic phases at high density all involve the strange quark

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Lattice QCD: precision studies of nucleon-hyperon interactions

However: an important piece of the problem can be addressed

Exotic phases at high density all involve the strange quark

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Lattice QCD: precision studies of nucleon-hyperon interactions

EXASCALE!

Will we be ready?

What does it take?

• Can the physics problem productively consume a PFlops-year today?

• Is significant progress expected from an ExaScale machine?

• Does significant progress require an ExaScale machine?

QCD: lattice studies of cold matter & nuclei with A>5

QCD: hydrodynamics of heavy ion collisions; lattice QCD determination of critical point

QCD: hydrodynamics of heavy ion collisions; lattice QCD determination of critical pointStructure: time-dependent density functional studies of fission, reactions

QCD: lattice studies of nucleon properties, nucleon-meson interactions, multi-nucleon states & matrix elements, hot quark-gluon plasma, hadronic excited states, hyperons;

QCD: lattice studies of nucleon properties, nucleon-meson interactions, multi-nucleon states & matrix elements, hot quark-gluon plasma, hadronic excited states, hyperons;Astro: Major advances in supernova simulations

QCD: lattice studies of nucleon properties, nucleon-meson interactions, multi-nucleon states & matrix elements, hot quark-gluon plasma, hadronic excited states, hyperons;Astro: Major advances in supernova simulationsNuclear structure: Major advances in nuclear structure calculations using GFMC, no-core shell model, DFT

What nuclear theory challenges could efficiently use an Exascale computer today?

To realize extreme computing in nuclear physics requires minds as well as machines

• Theory: effective field theory techniques, algorithm development, new formulations of old problems, improved Hamiltonians...

• Computer science: algorithm development, exploiting multi-core chips, parallel architecture, stability with imperfect hardware...

GETTING READY FOR EXASCALE

• Programs such as SciDAC (DOE) and CDI (NSF) have a big role to play

•Access to time on machines of varying sizes is critical: local TFlops clusters to PFlops national class platforms

•Topical collaborations (2007 Long Range Plan recommendation) would be invaluable for computational nuclear theory

WITH - AND ONLY WITH - EXASCALE:

•A unified nuclear theory, from QCD to heavy nuclei

•Nucleon and nuclear structure becomes a precision science, complementing major experimental programs (~1% errors)

•A new era for the simulation & prediction of nuclear dynamics and reactions from fundamental interactions (fission, fusion, stellar explosions, heavy ion collisions..)

Major Issues in Nuclear Physics Aided by Massive Computation

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