Space Telescope Science Institute, Feb. 2006

Rocky Kolb, Fermilab & ChicagoSpace Telescope Science Institute, Feb. 2006

Rocky Kolb, Fermilab & Chicago

(Two wildly unpopular ideas about)(Two wildly unpopular ideas about)

Precision CosmologyPrecision CosmologyPrecision CosmologyPrecision Cosmology

MAPWMAP

CDMCDMCDMCDM

• Inflation-produced perturbations• Baryo/leptogenesis

Mission accomplished …Mission accomplished …Mission accomplished …Mission accomplished …

… … or premature jubilation?or premature jubilation?… … or premature jubilation?or premature jubilation?

What Is Dark Matter?What Is Dark Matter?What Is Dark Matter?What 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

dynamics x-ray gaslensing

MatterMatterMM MatterMatterMM

power spectrum

cmb simulations

i iC

QSO 1937-1009

Ly

Burles et al.

BaryonsBaryonsB B

hhBaryonsBaryonsB B

hh2

BWMAP: 0.0224 0.0009h

Tytler

matter?matter?

• Modified Newtonian dynamics

• Black holes

• Size challenged stars

• Planets Micro

lensin

g

• Dwarf starsbrown red

white

• Modified Newtonian dynamics

• Undiscovered new particle (WIMP)

matter?matter?

Cold Thermal RelicsCold Thermal RelicsCold Thermal RelicsCold Thermal Relics

freeze out

actual

equilibrium

X

T/MX

1010

Rel

ativ

e ab

un

dan

ce

1510

2010

510

010

1 2 31 10 10 10

/e M T

X A(independent of mass)

X A

X X q q

X

X

q

q

X S

X q X q

X

q q

X

X P

q q X X Xq

q X

X X AAX X AA

Cold Thermal RelicsCold Thermal RelicsCold Thermal RelicsCold Thermal Relics

freeze out

actual

equilibrium

X

T/MX

1010R

elat

ive

abu

nd

ance

1510

2010

510

010

1 2 31 10 10 10

/e M T

• s-wave or p-wave?• annihilation or scattering cross section?• co-annihilation?• sub-leading dependence on mass, g*, etc.• targets are nuclei (spin-dependence)

Not quite so clean:

Cold Thermal RelicsCold Thermal RelicsCold Thermal RelicsCold Thermal Relics

Seeking SUSYSeeking SUSYSeeking SUSYSeeking SUSYHierarchy problem:• fundamental scale is Planck mass*• observe particles with mass much less than Planck mass

o gauge bosons protected by gauge symmetryo fermions protected by chiral symmetryo scalars (e.g., Higgs) defenseless!

• introduce supersymmetry to protect scalars

Supersymmetric Standard Model: 105 parameters

Constrained Minimal Supersymmetric Standard Model: 3 parameters:

Lightest supersymmetric particle (LSP) stable: neutralino?

1/ 2 0tan , , , sign( )m m

* Assumed here to be 1/ 2NG

• Direct detection (S)

More than a dozen experiments

• Indirect detection (A)

Annihilation in sun, Earth, galaxy. . .

neutrinos, positrons,

antiprotons, rays, . . .

• Accelerator production (P)

Tevatron, LHC, ILC

Cold Thermal Relics (neutralino)Cold Thermal Relics (neutralino)Cold Thermal Relics (neutralino)Cold Thermal Relics (neutralino)

• SUSY shaded areas

• Probing significant regions of MSSM model space

• Light-mass region largely ruled out

• Another factor of 100 may be needed Combined

Soudan limits

DAMA NaI/1-4 3region

ZEPLIN I

EDELWEISS

Cryogenic Dark Matter Search

Cold Thermal RelicsCold Thermal RelicsCold Thermal RelicsCold Thermal Relics

Muon Neutrinos From the SunMuon Neutrinos From the SunMuon Neutrinos From the SunMuon Neutrinos From the Sun

“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.

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

SIZESIZEDOESDOESMATTER

MATTER

SIZESIZEDOESDOESMATTER

MATTER

visit wimpzillas.com

example ofnon-thermaldark matter

WIMPZILLASWIMPZILLASWIMPZILLASWIMPZILLAS

TheTheVacuumVacuum

TheTheVacuumVacuum ofofofof

Quantum UncertaintyQuantum UncertaintyQuantum UncertaintyQuantum Uncertainty

quark

anti particle particle

e+ e-

W+

W-

anti-quark

Disturbing the VacuumDisturbing the VacuumDisturbing the VacuumDisturbing the Vacuum Strong gravitational field particle production

(Hawking radiation)

Black

Hole

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

• require (super)massive particle “X”

• stable (or at least long lived)• initial inflationary era followed by radiation/matter

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!

Inflaton mass (in principle measurable from gravitational wave background, guess ) may signal a new mass scale in nature.

Other particles may exist with mass comparable to the

inflaton mass.

Conserved quantum numbers may render the particle stable.

GeV1012

Superheavy ParticlesSuperheavy ParticlesSuperheavy ParticlesSuperheavy Particles

• supermassive: GeV (~ 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)?

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

WIMPZILLA Footprints:WIMPZILLA Footprints:WIMPZILLA Footprints:WIMPZILLA Footprints:

Isocurvature modes: CMB, Large-scale structure

Decay: Ultra High Energy Cosmic Rays

Annihilate: Galactic Center, Sun

Direct Detection: Bulk, Underground Searches

WIMPZILLA DecayWIMPZILLA DecayWIMPZILLA DecayWIMPZILLA Decay

X UHE cosmic rays

GeV = eV

Kuzmin & Rubakov; Birkel & Sarkar; Ellis, Gelmini, Lopez, Nanopoulos & Sarkar; Berezinsky, Kachelriess, & Vilenkin;Benakli, Ellis, & Nanopoulos; Berezinsky, Blasi, & Vilenkin; Blasi; Berezinsky & Mikhaliov;Dubovsky & Tinyakov; Medina-Tanco & Watson;Blasi & Seth; Ziaeepour; Crooks, Dunn, & Frampton

UHE cosmic rays mostly photons; characteristic spectrum; UHE neutrinos; lower-energy crud;

clumping anisotropies

WIMPZILLA DecayWIMPZILLA DecayWIMPZILLA DecayWIMPZILLA DecayBusca,Hooper,Kolb

MX eV

p

extra-galactic

Auger data

WIMPZILLAor

Dark MatterDark MatterDark MatterDark Matter

WIMP

SIZESIZEDOESDOESMATTER

MATTER

SIZESIZEDOESDOESMATTER

MATTER

What is Dark Energy?What is Dark Energy?What is Dark Energy?What is Dark Energy?

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

-- Virginia WoolfA Room of Ones Own

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

Rie

ss e

t al

. (20

04)

cosmological constant, some changing non-zero vacuum energy, or some unknown systematic effect(s)

Ein

stein-d

e Sitter: flat,

matter-d

om

inated

mo

del

(maxim

um

theo

retical bliss)

The case for :1) Hubble diagram dL(z)2) subtraction

dynamics x-ray gaslensing

i iC C 3H028G

power spectrum

cmb simulations

TOTAL (CMB), M

SubtractionSubtractionSubtractionSubtraction

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

Rie

ss e

t al

. (20

04)

cosmological constant, some changing non-zero vacuum energy, or some unknown systematic effect(s)

Ein

stein-d

e Sitter: flat,

matter-d

om

inated

mo

del

(maxim

um

theo

retical bliss)

The case for :1) Hubble diagram dL(z)2) subtraction

3) age of the universe4) structure formation

Illogical magnitude (what’s it related to?):

4 430 -3 4 310 g cm 10 eV 10 cm

Cosmo-illogical constant?Cosmo-illogical constant?Cosmo-illogical constant?Cosmo-illogical constant?

2 229 338 10 cm 10 eVG

Illogical timing (why now?):

BBNEWKGUT

M R

REC

anthropic principle

scalar fields

Practical Tools for Dark EnergyPractical Tools for Dark EnergyPractical Tools for Dark EnergyPractical Tools for Dark Energy

How Far Will They Go?How Far Will They Go?

How Far Will They Go?How Far Will They Go?

Do we “know” there is dark energy?Do we “know” there is dark energy?Do we “know” there is dark energy?Do we “know” there is dark energy?

• Assume model cosmology:

– Friedmann model: H2 k/a2 = G/

– Energy (and pressure) content: M R +

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

• Calculate observables dL(z), dA(z),

• Compare to observations

• Model cosmology fits with , but not without

• All evidence for dark energy is indirect: observed H(z) is not• described by H(z) calculated from the Einstein-de Sitter model

• Age of the universe 0 1

z dzt z

z H z

Evolution of Evolution of H(z)H(z): a Key Quantity: a Key QuantityEvolution of Evolution of H(z)H(z): a Key Quantity: a Key Quantity

Many observables based on the coordinate distance r(z)

20 001

zr z tdr dt dz

a t H zkr

1Ld z r z z • Luminosity distance

Flux = (Luminosity / dL)

1A

r zd z

z

• Angular diameter distance

Angular diameter (Physical size / dA)

2dV z r z

dz d H z

• Comoving number counts N / V (z)

Robertson–Walker metric 2

2 2 2 2 221

drds dt a t r d

kr

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) – “Just” , a cosmological constant– If not constant, what drives dynamics (scalar field)

• Gravity (modify left-hand side of Einstein equations)– Beyond Einstein (non-GR: branes, etc.)– (Just) Einstein (GR: Back reaction of inhomogeneities)

H(z) not given by

Einstein–de Sitter

H G MATTER

Modifying the left-hand sideModifying the left-hand sideModifying the left-hand sideModifying the left-hand side• Braneworld modifies Friedmann equation

• Phenomenological approach

• 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

Freese & Lewis 12

cutoff1n

H A

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 Newtonian gravity at large distances– no Lorentz violation– no extra dimensions, bulks, branes, etc.– no faith-based (anthropic) 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 InhomogeneitiesHomogeneous model Inhomogeneous model

3

h

h h

h h h

V a

H a a

3

i

i i

i i i

x

V a

H a a

h i x

We (Kolb, Matarrese, Riotto + others) think not!

?h iH H

Acceleration from inhomogeneitiesAcceleration from inhomogeneitiesAcceleration from inhomogeneitiesAcceleration from inhomogeneities• View scale factor as zero-momentum mode of gravitational field

• In homogeneous/isotropic model it is the only degree of freedom

• Inhomogeneities: non-zero modes of gravitational field

• Non-zero modes interact with and modify zero-momentum mode

cosmology scalar-field theory

zero-mode a hi (vev of a scalar field)

non-zero modes inhomogeneities thermal/finite-density bkgd.

modify a(t) modify h(t)i e.g., acceleration e.g., phase transitions

Cosmology scalar field theory analogue

physical effect

Different approachesDifferent approachesDifferent approachesDifferent approaches

• Expansion rate of an

inhomogeneous Universe expansion rate of homogeneous Universe with hi

• Inhomogeneities modify zero-mode [effective scale

factor is aD VD]

• Effective scale factor has a (global) effect on observables

• Potentially can account for acceleration without dark energy or modified GR

• Model an inhomogeneous Universe as a homogeneous Universe model with hi

• Zero mode [a(t) / V] is the zero mode of a homogeneous model with hi

• Inhomogeneities only have a local effect on observables

• Cannot account for observed acceleration

Standard approach Our approach

Inhomogeneities–CosmologyInhomogeneities–CosmologyInhomogeneities–CosmologyInhomogeneities–Cosmology

• Our Universe is inhomogeneous

• Can define an average density • The expansion rate of an inhomogeneous universe of average

density is NOT! the same as the expansion rate of a homogeneous universe of average density !• Difference is a new term that enters an effective Friedmann • equation — the new term need not satisfy energy conditions!

• We deduce dark energy because we are comparing to the wrong model universe (i.e., a homogeneous/isotropic model)

Inhomogeneities–exampleInhomogeneities–exampleInhomogeneities–exampleInhomogeneities–example

FLRW

FLRW00 00 00

2

00

, ,

, 8 ,

8 3

3 8

G x t G t G x t

G t G x t GT x t

a GG

a G

• (aa) is not G

• Perturbed Friedmann–Lemaître–Robertson–Walker model:

Kolb, Matarrese, Notari & Riotto

• (aa is not even the expansion rate)

• Could G play the role of dark energy (energy conditions)?

• How large could it be?

Many issues:• non-perturbative nature• shell crossing• comparison to observed LSS• gauge/frame choices• physical meaning of coarse graining

Program:

• can inhomogeneities change effective zero mode?• how does (does it?) affect observables?• can one design an inhomogeneous universe that accelerates?• could it lead to an apparent dark energy?• can it be reached via evolution from usual initial conditions?• does it at all resemble our universe?• large perturbative terms resum to something harmless?

TolmanTolman––Bondi–LemBondi–LemaîaîtretreTolmanTolman––Bondi–LemBondi–Lemaîaîtretre

open

closed

L

r0

2 2,2 2 2 2 2

221

1ra r dr

ds dt a r da k r r

• dust model: a

• spatial curvature: k for r r

kforr r L

• “Friedmann” equation

• Not to be regarded as• a realistic model

2

03 2

8

3

k ra G

a a a

Nambu & Tanimoto (gr-qc/0507057)[also Moffet]

Observational consequencesObservational consequencesObservational consequencesObservational consequencesTomita, 2001• Spherical model

– Inner underdense 200 Mpc region

– Compensating high-density shell

– Then Einstein–de Sitter

• Calculate dL(z): fit SNIa data with

!

• Calculate Cl : first peak about right!

Alnes, Amarzguioui, Grønastro-ph/0512006

Observational consequencesObservational consequencesObservational consequencesObservational consequences• It’s the goal!

• Eventually predict dL(z), dA(z), w, wa , w0,

• Growth of structure in FLRW:

Growth of structure in this scenario?

• Shear?

00

2 4 ji i j

j

H G

H changes any additional terms on r.h.s?

Acceleration in our local Hubble patch if the mean rarefaction factor (w.r.t. the underlying FRW model) grows fast enough to overshoot the FRW background evolution.Kolb, Matarrese, Riotto

DON’T KILL

ROCKY

Acceleration without dark energy!!!!!Acceleration without dark energy!!!!!Acceleration without dark energy!!!!!Acceleration without dark energy!!!!!

The nature of dark energy is a complex natural phenomenon.

There are no simple, elegant, compelling explanations.

Space Telescope Science Institute, Feb. 2006

Rocky Kolb, Fermilab & ChicagoSpace Telescope Science Institute, Feb. 2006

Rocky Kolb, Fermilab & Chicago

(Two wildly unpopular ideas about)(Two wildly unpopular ideas about)

Acceleration from inhomogeneitiesAcceleration from inhomogeneitiesAcceleration from inhomogeneitiesAcceleration from inhomogeneities• We assume that observables (dA, dL, z, etc.) are modified if • the effective scale factor is modified.

• We can only show this for unrealistic models.

• We must also assume that there will be no (or little) anisotropy • (shear).

Acceleration from inhomogeneitiesAcceleration from inhomogeneitiesAcceleration from inhomogeneitiesAcceleration from inhomogeneities

• We do not use super-Hubble modes for acceleration.

• We do not depend on large gravitational potentials such as black holes and neutron stars.

• We calculate claim the back reaction in a reference frame comoving with the matter—other frames give spurious results.

• We demonstrate large corrections in the gradient expansion, but the gradient expansion technique can not be used for the final answer—so we have indications (not proof) of a large effect.

• The basic idea is that small-scale inhomogeneities “renormalize” the large-scale properties.

InhomogeneitiesInhomogeneities––smoothingsmoothingInhomogeneitiesInhomogeneities––smoothingsmoothing

• Matter smoothing is straightforward (particles fluid)• Space-time metric smoothing not straightforward!• Consider Einstein equations on a scale where the universe is• inhomogeneous and anisotropic

– Smooth on some larger scale

– Smoothing & evolution (the field equations) do not commute– Einstein tensor computed from smoothed metric – is not the same as the Einstein tensor computed– from the smoothed stress-energy tensor

– Difference is a new term that enters an effective Friedmann– equation, new term need not satisfy energy conditions!

– We deduce dark energy because we are comparing to the – wrong model universe (i.e., a homo/iso model)

Ellis, Barausse, Buchert, Ellis, Kolb, Matarrese, Notari, Räsänen, Riotto, Schwarz