Cosmology Update KCL

8/12/2019 Cosmology Update KCL

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Update on Cosmic Inflation

and Dark Stuff

Malcolm Fairbairn, KCL Physics


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Cosmic inflation.

Not to be confused with


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Where has Scientific thinking taken us?

What is the state of the art?

Chemistry

Atomicphysics

NuclearPhysics

Particle

Physics

On small scales.

On large scales.

Newtonian

Gravity

General

Relativity


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Particle Physics / Quantum Field Theory

We think particles are made out of oscillations of quantum fields.

Quantum fields can be thought of as oscillators spread out through space-time

which are coupled to each other with springs so that any oscillation would move.

Note in the analogy, the position of the weight does notmove in real space but

in an internal quantum field space.


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Force as derivative of potential

On a map, contour lines are lines of constant height, which

are also lines of constant gravitational potential energy.

You roll down the hill from high potential energy to

low potential energy.

Here, derivative isve

so Force is +ve

Here, derivative is positive

so Force is negative


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There are a

different set of

pendulums for

each different

kind of particle

We haveidentified 17

different kinds of

particles

This is the

standard model

of particle

physics


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What is Einsteins

most important equation?


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What is Einsteins

most important equation?

E=mc2

NO!


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Friedman(1888-1925)


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Einstein modified his theory

to stop the Universe from

Expanding

Cosmological constant


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Edwin Hubble(1889-1953)


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Galaxies actually are moving away from each other (and us)


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So, the Universe itself expands naturally in General Relativity,

and our observed Universe also expandsGREAT THEORY!!

However, there are some problems.


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Before and after recombination


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Horizon Problem

Last Scattering surface~


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Fi ld th ff t i f U i


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Field theory affects expansion of Universe

Quantum fields have potential energy and kinetic energy.

f

When the field is up here it has

only potential energy

When the field is down here it

has mostly kinetic energy

r = Potential + Kinetic Energy

E i f U i ff t Fi ld Th


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Expansion of Universe affects Field Theory

r = Potential + Kinetic Energy, leads to expansion

Acts like friction on the oscillating pendulum, normally the

energy is quickly lost

E i f U i ff t Fi ld Th


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Expansion of Universe affects Field Theory

r = Potential + Kinetic Energy, leads to expansion

If the expansion is great enough, the oscillation is completely

damped, field is trapped.


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End of Inflation - Reheating

f

Eventually, the field f slowly slides down the potential and as it does, the friction

goes away. Eventually ends up oscillating around the bottom of the potential.

Coupling between inflaton and other Standard model

fields creates lots of random fluctuations in all the fields

Corresponds to lots of high energy particlesUniverse becomes HOT


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Now were cooking on gas!!!

Plasmaquark-gluon-electron-muon-tau-neutrino-photon-dark-matter


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So at this time after

inflation, everywhere

in the universe is like

the centre of the

LHC, except probablyat least 1,000,000

times more

energetic


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Quark Gluon Phase transition to Nuclei

(1 microsecond has now passed)


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Around 1 second to 1 minute after the big bang

Primordial Nucleosynthesis


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Primordial Nucleosynthesis

Here is the complete chain.

EVERYTHING else is produced

later in stars.


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Then wait.

Universe just full of fire for around

400,000 years.


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Inflation Solves the Horizon Problem

Vf)~constant

Exponential expansion allow

signals from a small region to bespread out all over the sky. Can

explain why they have the same

temperature. Also dilutes the

density of monopoles and string

exponentially from before

inflation, and makes the vacuumthe same everywhere after

inflation. Explains why we dont

see them.

I fl ti E l i h th U i i fl t


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Inflation Explains why the Universe is so flat

The exponential period of

expansion flattens out any

spatial curvature. Thisexplains why the Universe is

so flat.

I fl ti d th O i i f P t b ti


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Inflation and the Origin of Perturbations

f

The expansion leads to a cosmological horizon, which means that the size of the

Universe is rather small during inflation. This leads to fluctuations in the value of f

due to the Uncertainty principle. In one Hubble time Dt ~ 1/H the field fwillfluctuate in a random direction an amount (on average) df~ H.

Fluctuations in f

Usually, the amount the field moves due to

these fluctuations is tiny compared to the

classical slow roll of the field down thepotential. However, because a change in

the field leads to a change in the density,

they represent density fluctuations.

After inflation, the field fwill decay into

other particles like photons and quarks,electrons etc. Where the density of V(f)

was higher, the density of matter will be

higher, hence the fluctuations.


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Dark Matter


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Whatsall the rest???

10-29 4 x 10-31

2


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I have a good ideaevery two years.Give me a topic, Iwill give you theidea!

Fritz ZwickyComa Cluster 1933

velocity of galaxies in the cluster is too

large for the visible mass of the cluster


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WIMPS - Weakly Interacting Massive Particles


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Direct detection of dark matter


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Direct detection of dark matter

CDMS-II Recent Data 1304 4279


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CDMS-II Recent Data 1304.4279

5.4% prob!!!

CDMS II i l t 8 6 G V?


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CDMS-II signal at 8.6 GeV?

WIMP indirect detection


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WIMP indirect detection

Dark Matter Self-Annihilation


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Dark Matter Self Annihilation


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Fermi Signal

Boyarsky et al. 1012.5839


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Has Fermi detecteddark matter

annihilation at the

galactic centre?

Hooper and Goodenough.

arXiv:1010.2752

Alternative explanation for spectrum


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Boyarsky et al 1012.5839 Chernyakova et al. 1009.2630

Hooper+Goodenough purported DM spectrum

p p


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Positrons!


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So Far AMS hasnt changed the Situation


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Where are we now?


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Possible astrophysical origin of electrons/positrons

10 GeV10 TeV

SNR - Secondary Pulsars - Primary

Where are we now?


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Dark Energy


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The star which burns twice as bright burns half as long

from the film Bladerunner

Not true it is 61% as long


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Time and the HR diagram


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Time and the HR diagram

Age of the Universe from Globular Clusters


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Gives us a figure of 12 billions years


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Universe used to expand faster than today


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Universe used to expand faster than today...

distance


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velocity

If expansion rate was always the same, should get straight line

However, the Universe used to

be denser - expanding faster,

decelerating over time.

Towards

BIG BANG


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If the Universe just

contained matter, its

age would be about

9.2 billion years!!

i.e. Not old enoughto contain the stars

inside it!

What is going on?


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Type 1a supernovae as

Standard candles

distance


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velocity

What we should see:-

deceleration

What we do see:-

deceleration here

acceleration here


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THE REAL STANDARD COSMOLOGICAL MODEL


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THE REAL STANDARD COSMOLOGICAL MODEL

baryons = 100%

BUT THE UNIVERSE WE LIVE IN

baryons = 4%, dark matter = 24%, dark energy = 72%

NONE STANDARD ??


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There is an Elephant in the Room...


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Very very occasionally a random fluctuationDoes the Universe


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f

Very very occasionally, a random fluctuation

will put the field a bit further up the hill

than normal. In that small region,

expansion will increase, so it will become a

bigger region, and because df ~ H thefluctuations in that region will be bigger, so

the field might go even higher up the hill,

expansion would be even faster and

fluctuations even bigger.

It is clear that the majority of the Universe

will be inflating very rapidly with big

quantum fluctuations and only occasionally

will a part of the Universe drop out of this

inflation due to a random fluctuation in the

other direction so that classical slow roll willtake over. This is chaotic inflation.

create itself?

Chaotic Inflation

Chaotic Inflation


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Chaotic Inflation

In each different pocket where the field

drops out of inflation, there are many

different ways that the Universe couldcool, leading to many different kinds of

symmetry breaking and many different

kinds of Universe and even laws of

physics.

We just happen to live in one Universe

in the multiverse which is good for us.

Alternatively, in order for us to exist as

we do, we need to live in one verysimilar to the one we live in.

Our little Universe is the way it is

because if it were different we would

not be here to observe it. This is called

the WEAK ANTHROPIC PRINCIPLE.


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Other Research in Kings Physics


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Different scales in the Universe


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Different scales in the Universe

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Biological Imaging


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Biological Imaging

Biological Imaging
http://www.greenspine.ca/media/rainbowtadpole1_c.jpg


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proteins in a biological membrane

2000 by W. H. Freeman and Company. All rights reserved.


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Fluorescent Green star Coral

Imaging Intercellular Communication


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g g

Processes occur very quickly -

also very few photons

Immune synapse formation

involves rearrangement ofproteins at intercellular contact of

Natural Killer cell and target cell

Immune synapse formationstrategy of body to fight disease

Natural

Killer

cell

Target

cell

Make every photon count!


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Microchannel plate (MCP) image

intensifiernight vision deviceGlass capillaries(latest technology - etched silicon)

Acquisition speed limited by

frame rate of camera


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Next step


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Next step

Put detector on microscope and look atfluorescent cell samples to help biologist

understand how diseases work.

Examples: cancer, asthma, epilepsy


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MSci year project


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Atomic and Molecular Modelling


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Atomic and Molecular Modelling

CO

H

Pt

Fe

Na

structures, properties, processes

Schrdinger equation

V2m

t

2

2

=

i


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Bioactivity of bone implants


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Bioactivity of bone implants

Bioactivity: Capacity of a material

of promoting the spontaneousdeposition of bone material on its

surface in the body environment

(osteointegration)


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SEM analysis of TiN-coated explants


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S a a ys s o coated e p a ts

Analysis of several samples explanted after 5 to 10 years

In most cases a compact deposit is present on the TiN-coated explant surface


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Kings X-Ray research today:-


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King s X-Ray research today:-

Adaptive optics

Very Large Telescope, Chile


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X-ray


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DNA damage in a mammalian cell

induced by focused X-rays. The brightarea, which is less than 1 micrometre

in size, shows the damaged area.

[Work done in conjunction with the

Gray Cancer Institute]

adaptive

optics


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History of Kings Physics


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Sir Charles Wheatstone

(18021875)


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James Clerk Maxwell

(18311879)



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Professor CG Barkla FRS

(19091914)1917 Nobel Prize for Physics for his discovery that x-rays

emitted by different elements have characteristic energies.



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Sir Owen Richardson FRS

(19141944)

1928 Nobel Prize winner for 1928 for work on thermionic emission;

the invention of the thermionic valve revolutionised

telecommunications and allowed the development of radio and

television.



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Sir Edward Appleton FRS

(19241936)

Nobel Prize for his work on the Physics of the upperatmosphere, and in particular for his discovery of the

layer of ionised upper atmosphere that is still referred to

as the Appleton Layer.



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Professor Maurice Wilkins FRS

(1916-2004)

shared the 1962 Nobel Prize for Physiology with James

Watson and Francis Crick for determining (by x-ray diffraction)

the structure of DNA.



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Dr Rosalind Franklin(1920-1958)


Famous Ex-Undergraduates:-


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Famous Ex Undergraduates:

Arthur C. Clarke Peter Higgs

How do we teach?


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How do we teach?

Lectures (about 9 hours/week)

Supported by tutorials (1 hour/week)

Tutor sessions (as and when needed) Lab sessions (1 day/week)

Personal study (as needed)


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What will you do in the third year?


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What will you do in the third year?

Statistical Mechanics

Quantum Mechanics

Optics

Solid State Physics

Third year project

Literature review

Choice of many: General Relativity, ParticlePhysics, Medical Imaging, University

Ambassador scheme, Physics of Life at a small

scale Maths III


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What does KCL Physics have to offer you


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y y

Significant recent expansion -> 30 staff

Normal first year entry is around 90 Full time

students (about 110 total, half joint honours)

This is a favourable staff-student ratio

World class research means world class teaching

We strive to ensure that students are more than

just a number

The Maxwell Society


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yThe Maxwell Societyis run by the students and staff. Lots of events

(serious and otherwise) including the Maxwell Lecture series and the

Cumberland Lodge weekend.

http://www.kclmaxsoc.org.uk/

What do Kings physicists do?


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g p y

Material Scientist - Pharmaceutical company

Medical Technical Officer

Innovation OfficerInstitute of Physics

Quant (finance)

Reporter IT ConsultantIBM

Production Co-ordinatorTV Production Company

Science and technology advisorDept. Transport

Defense industry

Further study

Latest Stats, 2011 graduating Year6 months after graduation


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6 months after graduation

28%

3%

5%

3%50%

8%3%

0%

Full time work

Part time work

Voluntary work

Work and studyStudy

Unemployed

Unavailable

Other

100% of the full time work people are in graduate level jobs.

Median Salary 26,500


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Thank you for your attention!

Study Destinations


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y

MSc PhysicsMSc Physics and Engineering in Medicine

Particle Physics

PGCE Science

PGCE Secondary School

PHYSICSPractical Teaching

Radiation Physics

Risk Management and Financial Engineering

ACA

MRes in Photonics Systems Development

MSc Computer Science

MSc Environmental Technology

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Cosmology Update KCL

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