Rocky Kolb, University of ChicagoRocky Kolb, University of ChicagoVenice March 2007Venice March 2007Rocky Kolb, University of ChicagoRocky Kolb, University of ChicagoVenice March 2007Venice March 2007

CDM:CDM: Beyond the Standard Model Beyond the Standard ModelCDM:CDM: Beyond the Standard Model Beyond the Standard Model

Precision cosmologyPrecision cosmology

MAPWMAP

Cold Dark Matter: 25%

Dark Energy (): 70%

Stars:0.5%

Free H & He:4%

Chemical Elements: (other than H & He)0.025%

Neutrinos: 0.47%

CDMCDMCDMCDM

inflationary perturbations baryo/lepto genesis

Radiation: 0.005%

The construction of a model … consists of snatching from the enormous and complex mass of facts called reality a few simple, easily managed key points which, when put together in some cunning way, becomes for certain purposes a substitute for reality itself.

Evsey DomarEssays on the Theory of Economic Growth

CDM: reality or substitute for it?

It hardly matters to me whether he [Copernicus] claims that Earth moves or that it is immobile, so long as we get an absolutely exact knowledge of the movements of the stars and the periods of their movements, so long as both are reduced to altogether exact calculation.

Gemma Frisius 16th century Dutch astronomer

Standard cosmological model*Standard cosmological model*Standard cosmological model*Standard cosmological model*

* Do we want one? The goal is not a standard one, but the correct one!

• Radiation

• Bright baryons

• Neutrinos

• Dark baryons

• Baryo/leptogenesis

• Inflation

• Dark matter

• Dark energy

• Hypotheses?

• Saving the appearances?

• Epicycles?

Cold Dark Matter: 25%

Dark Energy (): 70%

Stars:0.5%

Free H & He:4%

Chemical Elements: (other than H & He)0.025%

Neutrinos: 0.47%

CDMCDMCDMCDM

inflationary perturbations baryo/lepto genesis

Radiation: 0.005%

It’s OK in practice, but…How does it work in theory?

Epicycle I – Dark EnergyEpicycle I – Dark EnergyEpicycle I – Dark EnergyEpicycle I – Dark Energy

“In questions like this, truth is only to be had by laying together many variations of error.”

-- Virginia Woolf

A Room of Ones Own

What is the nature of dark energy

3) age of the universe4) structure formation

High-z SNe are fainter than expected in the Einstein-deSitter model

The case for :1) Hubble diagram2) subtraction

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itter: sp

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supernova redshift z

cmb

dynamics x-ray gaslensing

i iC C H G

power spectrum

simulations

TOTAL (CMB) M

SubtractionSubtractionSubtractionSubtraction

TOTALM

How do we “know” there is dark energy?How do we “know” there is dark energy?How do we “know” there is dark energy?How do we “know” there is dark energy?• Assume model cosmology:

– Einstein equation symmetry Friedmann equation: H(z)

– Energy (and pressure) content: matter, radiation, Lambda

– Input or integrate over cosmological parameters: H, B, etc.

• Calculate H(z)

• Calculate observables: dL(z) , dA( z ), …

• Compare to observations

• Model cosmology fits with but not without

All evidence for dark energy is indirect: observed expansion history is not as calculated from the Einstein-de Sitter model (homogeneous, matter-dominated, spatially flat model w/o

• Age of the universe

Evolution of Evolution of H (H (inin z z oror t) t) is a key quantity is a key quantityEvolution of Evolution of H (H (inin z z oror t) t) is a key quantity is a key quantity

Many observables based on H(z)

• Luminosity distance Flux = (Luminosity / dL)

• Angular diameter distance Physical size / dA

• Volume (number counts) N / V (z)

• Distances

Take sides!Take sides!Take sides!Take sides!

• Can’t hide from the data – CDM too good to ignore– SNIa– Subtraction: – Age– Large-scale structure– …

• Dark energy, (modify right-hand side of Einstein equations)

1. Constant (“just” Einstein’s cosmological constant )

2. Not constant (dynamics driven by scalar field: M eV)

• Gravity (modify left-hand side of Einstein equations)

3. Beyond Einstein (non-GR: branes, etc.)

4. (Just) Einstein (GR: back reaction of inhomogeneities)

H(z) not given by

Einstein–de Sitter

G G T(matter)

anthropic principle(the landscape)

scalar fields(quintessence)

Tools for the right-hand sideTools for the right-hand sideTools for the right-hand sideTools for the right-hand side

Modifying the left-hand sideModifying the left-hand sideModifying the left-hand sideModifying the left-hand side

• Braneworld modifies Friedmann equation

• Gravitational force law modified at large distance

• Tired gravitons

• Gravity repulsive at distance R Gpc

• n = 1 KK graviton mode very light, m (Gpc)

• Einstein & Hilbert got it wrong

• Backreaction of inhomogeneities

Five-dimensional at cosmic distances

Deffayet, Dvali& Gabadadze

Gravitons metastable - leak into bulkGregory, Rubakov & Sibiryakov;

Dvali, Gabadadze & Porrati

Kogan, Mouslopoulos,Papazoglou, Ross & Santiago

Csaki, Erlich, Hollowood & Terning

Räsänen; Kolb, Matarrese, Notari & Riotto;Notari; Kolb, Matarrese & Riotto

Binetruy, Deffayet, Langlois

1 4 416S G d x g R R Carroll, Duvvuri, Turner, Trodden

Acceleration from inhomogeneitiesAcceleration from inhomogeneitiesAcceleration from inhomogeneitiesAcceleration from inhomogeneities

• Most conservative approach — nothing new – no new fields (like eV mass scalars)– no extra long-range forces– no modification of general relativity– no modification of gravity at large distances– no Lorentz violation– no extra dimensions, bulks, branes, etc.– no anthropic/landscape/faith-based reasoning

• Magnitude?: calculable from observables related to

• Why now?: acceleration triggered by era of non-linear structure

Acceleration from inhomogeneitiesAcceleration from inhomogeneitiesAcceleration from inhomogeneitiesAcceleration from inhomogeneities

Homogeneous model Inhomogeneous model

3

h

h h

h h h

a V

H a a

3

i

i i

i i i

x

a V

H a a

h i x

We think not!

?h iH H

Epicycle II – Dark matterEpicycle II – Dark matterEpicycle II – Dark matterEpicycle II – Dark matterWhat is dark matter?

“In questions like this, truth is only to be had by laying together many variations of error.”

-- Virginia WoolfA Room of Ones Own

cmb

dynamics x-ray gaslensing

power spectrum

simulations

MM MM

QSO1937-1009

Ly

Burles et al.

Tytler

BB BB

2BWMAP: 0.0224 0.0009h

• Modified Newtonian dynamics (MOND)

Dark Matter?Dark Matter?Dark Matter?Dark Matter?

MOND Takes a BulletMOND Takes a BulletMOND Takes a BulletMOND Takes a Bullet

• Black holes

• Size challenged stars

• Planets

• Dwarf starsbrown red white

• Modified Newtonian dynamics (MOND)

• Beyond the standard model (WIMP)

Dark Matter?Dark Matter?Dark Matter?Dark Matter?

Dark Matter?Dark Matter?Dark Matter?Dark Matter?

• neutrinos (hot dark matter)

WMAP + LSSWMAP + LSSWMAP + LSSWMAP + LSS

Dark Matter?Dark Matter?Dark Matter?Dark Matter?

• neutrinos (hot dark matter)

• sterile neutrinos, gravitinos (warm dark matter)

• axions, axion clusters

• LKP (lightest Kaluza-Klein particle)

• supermassive wimpzillas

• solitons (Q-balls; B-balls; Odd-balls, Screw-balls….)

• LSP (neutralino, axino, …) (cold dark matter)

axions

axion clusters

6 40

8 25

10 eV (10 g)

10 M (10 g)

Mass range

Noninteracting: wimpzillas

Strongly interacting: B balls

Interaction strength range

Disturbing the VacuumDisturbing the VacuumDisturbing the VacuumDisturbing the Vacuum

e e

E

e e

Particle creation in an external electric field

Particle creation if energy gained in acceleration over a Compton wavelength exceeds the particle’s rest-mass

new application: dark matter(Chung, Kolb, & Riotto; Kuzmin & Tkachev)

• require (super)massive particle “X”

• stable (or at least long lived)

Arnowit, Birrell, Bunch, Davies, Deser, Ford, Fulling, Grib, Hu, Kofman, Lukash, Mostepanenko, Page, Parker, Starobinski, Unruh, Vilenkin, Wald, Zel’dovich,…

first application:

(Guth & Pi; Starobinski; Bardeen, Steinhardt, & Turner; Hawking; Rubakov; Fabbi & Pollack; Allen)

Expanding Universe Particle CreationExpanding Universe Particle Creation Expanding Universe Particle CreationExpanding Universe Particle Creation

density perturbations from inflation

gravitational waves from inflation

It’s not a bug, it’s a feature!

• supermassive: GeV (~ 1012 GeV ?)

• abundance may depend only on mass

• abundance may be independent of interactions

– sterile?

– electrically charged?

– strong interactions?

– weak interactions?

• unstable (lifetime > age of the universe)?

– UHE cosmic rays?

Wimpzilla Characteristics:Wimpzilla Characteristics:Wimpzilla Characteristics:Wimpzilla Characteristics:

WIMPZILLAorWIMP

SIZESIZEDOESDOESMATTER

MATTER

SIZESIZEDOESDOESMATTER

MATTER

“For every complex natural phenomenon there is a simple, elegant, compelling,wrong explanation.”

- Tommy Gold

The nature of dark matter is a complex natural phenomenon.

The neutralino is a simple, elegant, compelling explanation.

CDM:CDM: Beyond the Standard Model Beyond the Standard Model

(OR NOT!)(OR NOT!)

CDM:CDM: Beyond the Standard Model Beyond the Standard Model

(OR NOT!)(OR NOT!)

Rocky Kolb, University of ChicagoRocky Kolb, University of ChicagoVenice March 2007Venice March 2007Rocky Kolb, University of ChicagoRocky Kolb, University of ChicagoVenice March 2007Venice March 2007