Accelerators in the Universe March 2008 Rocky Kolb University of Chicago Accelerators in the Universe March 2008 Rocky Kolb University of Chicago

Accelerators in the Universe March 2008Accelerators in the Universe March 2008Rocky Kolb University of ChicagoRocky Kolb University of Chicago

Cold Dark Matter: (CDM) 25%

Dark Energy (): 70%

Stars:0.8%

H & He:gas 4%

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

Neutrinos: 0.17%

Radiation: 0.005%

CDMCDM

inflationary perturbations baryo/lepto genesis

Evidence for Dark EnergyEvidence for Dark Energy

Measuring the expansion history of the Universe

Friedmann equation (G GT) : Expansion rate H(z)

Equation of state parameter: w p wfor

if w w(a): 1

3 11 exp 3 1w

a

daz w aa

2 33 42 20 TOTAL

111 1 1 1 wR wMH z H zz z z

Hubble constant curvature matter radiation dark energy

CMB LSS CMB H(z)

Evolution of Evolution of H(z)H(z) Is a Key Quantity Is a Key Quantity

• Age of the universe 0 1

z dzt zz H z

Evolution of Evolution of H(z)H(z) Is a Key Quantity Is a Key Quantity

Many observables based on H(z) through coordinate distance r(z) 0

sin( ) 1

sinh

z dzr zH z

1Ld z r z z • Luminosity distance Flux = (Luminosity / dL

)

1A

r zd z

z

• Angular diameter distance Physical size / dA

• Volume (number counts) N / V (z)

Robertson–Walker metric 2

2 2 2 2 221

drds dt a t r dkr

2

21

r zdV drd

kr z

Ast

ier e

t al.

(200

6)*

SNLS

Einstein-de Sitter: spatially flat

matter-dom

inated model

(maxim

um theoretical bliss)

CDM

conf

usin

g as

tron

omic

al n

otat

ion

rela

ted

to s

uper

nova

brig

htne

ss

b

right

er

fa

inte

r

supernova redshift z


• High-redshift supernova are about a half-magnitude fainter than expected in the Einstein-de Sitter model.

• Statements such as there is dark energy, or that the Universe is accelerating are interpretations of the observations.

* Similar data from Essence collaboration.

M

1. Find standard candle (SNe Ia)2. Observe magnitude & redshift 3. Assume a cosmological model4. Compare observations & model

5. Fit needs cosmoillogical constant or vacuum energy density

Astier et al. (2006)SNLS

Einstein–de Sitter model

Evidence ForEvidence ForDark EnergyDark Energy

• Assumes w (i.e., )

• Assumes priors on H, spatial flatness, etc.

2.0

1.5

1.0

0.5

00 0.5 1.0

(The Unbearable Lightness of Nothing)

V 10–30 g cm!!!!!

V GV

length scale cm cmmass scale eV eV

Cosmoillogical ConstantCosmoillogical Constant

All fields: harmonic oscillators with zero-point energy


3 2 2 3C

all particles all particles

d k k m dk k

4

419 4 28 112 4

43 4 12 48 4

13

: relax, it's field theory

10 GeV : 10 eV 10 eV

10 GeV : 10 eV 10 eV

10 GeV:

C

C Pl Pl

C SUSY SUSY

C

M M

M M

44 16 4Observed 10 eV 10 eV

The quantum vacuum has a Higgs potential

Higgs potential gives mass to quanta like quarks and electrons

e,W, Z, quarks … photon

Higgs potential: eV


The Higgs Bison at FermilabThe Higgs Bison at Fermilab

100 4 48 4

45 4 32 4

GUT: 10 eV SUSY: 10 eV

EWK: 10 eV CHIRAL: 10 eV

high-temperature

low-temperature

V


-16 4OBSERVED: 10 eV

V


Extra DimensionsExtra Dimensions

Illogical timing (cosmic coincidence):

M R


We are here

Ast

ier e

t al.

(200

6)*

SNLS

Einstein-de Sitter: spatially flat

matter-dom

inated model

(maxim

um theoretical bliss)

CDM

conf

usin

g as

tron

omic

al n

otat

ion

rela

ted

to s

uper

nova

brig

htne

ss



3) Baryon acoustic oscillations4) Weak lensing

1) Hubble diagram (SNe)2) Cosmic Subtraction

The case for :5) Galaxy clusters6) Age of the universe7) Structure formation

* Similar data from Essence collaboration.

cmb

dynamics x-ray gaslensing

simulations

power spectrum

TOTAL M B

CMB many methods CMB/BBN


How We “Know” There’s Dark EnergyHow We “Know” There’s Dark Energy• Assume model cosmology:

– General relativity– Homogeneity & isotropy (FLRW)

– Energy (and pressure) content: M R +

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

• Calculate observables dL(z), dA(z), H(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 [spatially flat (from CMB) ; matter dominated (M)]

G = 8 G T00

H2 G/ k/a2

Taking Sides!Taking Sides!• Can’t hide from the data – CDM too good to ignore

– SNe– Subtraction: – Baryon acoustic oscillations– Galaxy clusters– Weak lensing– …

H(z) not given byEinstein–de Sitter

G(FLRW) G T(matter)

• Modify left-hand side of Einstein equations (G)

1. Beyond Einstein (non-GR: f (R), branes, etc.)2. (Just) Einstein (back reaction of inhomogeneities)

• Modify right-hand side of Einstein equations (T)1. Constant (“just” a cosmoillogical constant ) 2. Not constant (dynamics driven by scalar field: M eV)

Anthropic/LandscapeAnthropic/Landscape

• Many sources of vacuum energy

• String theory has many (?) vacua

• Some of them correspond to cancellations that yield a small

• Although exponentially uncommon, they are preferred because …

• More common values of results in an inhospitable universe

The Cosmological Constant and String Theory are made for each other…

Cosmological constant (): A result in search of a theoryString theory (or M-theory): A theory in search of a result

QuintessenceQuintessence• Many possible contributions. • Why then is total so small?• Perhaps unknown dynamics sets global vacuum energy equal to zero……but we’re not there yet!

V()

0

Requires m eV

QuintessenceQuintessence• Not every scalar potential works

– scaling, tracking, stalking potentials

• Couplings to matter (dark or otherwise)– mavens (mass varying neutrinos)– chameleon (dark energy is sensitive to environment)– changing fundamental constants (, etc.)

• k-essence– phantom, ghost condensate, Born-Infeld, …, Chaplygin gas

• Episodic dark energy (acceleration happens)

Punctuated Vacuum DominationPunctuated Vacuum Domination

Dodelson, Kaplinghat, Stewart

dark energy cosmic destiny

( ) 1 sinV e

Modifying 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 f (R)

• Backreaction of inhomogeneities

Five-dimensional at cosmic distancesDeffayet, 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 InhomogeneitiesHomogeneous model Inhomogeneous model

3

h

h h

h h h

a VH a a

3

i

i i

i i i

x

a VH a a

h i x

We think not!

?h iH H

(Buchert & Ellis)

Acceleration from InhomogeneitiesAcceleration from Inhomogeneities• No dark energy

• No acceleration in the normal sense (no individual fluid element accelerates)

Dark EnergyDark Energy• Many theoretical approaches (none compelling i.m.o.!)

• Perhaps nothing more can be done by theorists …

"Nothing more can be done by the theorists. In this matter it is only you, the astronomers, who can perform a simply invaluable service to theoretical physics."

Einstein in August 1913 to Berlin astronomer Erwin Freundlich encouraging him to mount an expedition to measure the deflection of light by the sun.

Dark EnergyDark Energy

Dark EnergyDark Energy• Many theoretical approaches (none compelling i.m.o.!)

• Perhaps nothing more can be done by theorists …

• Observables: dL(z) , dA(z) , distances, …

• … which (in FRW at least) all depend on H(z)

• Might as well assume FRW and measure(?) H(z)

• (Measure what you can as well as you can)

• Dark energy enters through (z), parameterized by w(z)

• Can’t measure a function; parameterize w(z)

0

0

1

1

a

a

w a w w a

zw z w wz

Dark EnergyDark Energy

: w ; wa

Quintessence: w / ; wa model dependent

Modified gravity: w can be less than ; wa unconstrained

Back reactions: ?????

0

0

1

1

a

a

w a w w a

zw z w wz

DETF* Experimental Strategy: DETF* Experimental Strategy: • Determine as well as possible whether the accelerating

expansion is consistent with being due to a cosmological constant. (Is w ?)

• If the acceleration is not due to a cosmological constant, probe the underlying dynamics by measuring as well as possible the time evolution of the dark energy. (Determine w(a).)

• Search for a possible failure of general relativity through

comparison of the effect of dark energy on cosmic expansion with the effect of dark energy on the growth of cosmological structures like galaxies or galaxy clusters. (Hard to quantify.)

* Dark Energy Task Force

H(z)

dL(z) dA(z) V(z)

baryonosc.

stronglensing

weaklensingSNIa clusters clusters

Alcock-Paczynski

Growth of structure

clusters weaklensing P(k,z)

Observational ProgramObservational Program

Test gravity

solarsystem

millimeterscale accelerators P(k,z)

2 4 0k k kH G

source?

stronglensing

Ast

ier e

t al.

(200

6)SN

LSEinstein-de Sitter:

spatially flatm

atter-dominated m

odel(m

aximum

theoretical bliss)

CDM

conf

usin

g as

tron

omic

al n

otat

ion

rela

ted

to s

uper

nova

brig

htne

ss



3) Baryon acoustic oscillations4) Weak lensing

1) Hubble diagram (SNe)2) Cosmic Subtraction

The case for :5) Galaxy clusters6) Age of the universe7) Structure formation

Supernova Type IaSupernova Type Ia• Measure redshift and intensity as function of time (light curve)

• Systematics (dust, evolution, intrinsic luminosity dispersion, etc.)

• A lot of information per supernova

• Well developed and practiced

• Present procedure:

– Discover SNe by wide-area survey on 4m-class telescopes

– Follow up spectroscopy (lots of time on 8m-class telescopes)

• The future:

– Better systematics (space-based?)

– Huge statistics (say with LSST) with photometric redshifts

• Each overdense region is an overpressure that launches a spherical sound wave

• Wave travels outward at c / 3

• Photons decouple, travel to us and observable as CMB acoustic peaks

• Sound speed plummets, wave stalls

• Total distance traveled 150 Mpc imprinted on power spectrum

WMAP

SDSS

Baryon Acoustic OscillationsBaryon Acoustic Oscillations

Mpc

dA

Mpc Hz

Baryon Acoustic OscillationsBaryon Acoustic Oscillations• Acoustic oscillation scale depends on Mh and Bh

(set by CMB acoustic oscillations)

• It is a small effect (B h ¿ M h)

• Dark energy enters through dA and H

• Virtues

– Pure geometry.

– Systematic effects should be small.

• Problems:

– Amplitude small, require large scales, huge volumes

– Photometric redshifts?

– Nonlinear effects at small z, cleaner at large z Dark energy not expected to be important at large z

Baryon Acoustic OscillationsBaryon Acoustic Oscillations

Weak LensingWeak Lensing

dark energyaffects growth

rate of M

4 LS

OS

DGMb D

dark energy

affects geometricdistance factors

observedeflection

angle

DOS

DLS

b

Weak LensingWeak Lensing

• Dominant source is PSF of atmosphere and telescope

• Errors in photometric redshifts

Space vs. Ground:• Space: no atmosphere PSF

• Space: Near IR for photo-z’s

• Ground: larger aperture

• Ground: less expensive

The signal from any single galaxy is very small,but there are a lot of galaxies! Require photo-z’s?

• Current projects– 100’s of sq. degs. deep multicolor data– 1000’s of sq. degs. shallow 2-color data

• DES (2010)– 1000’s of sq. degs. deep multicolor data

• LSST (2013)– full hemisphere, very deep 6 colors

Systematic errors: The Landscape:

Galaxy ClustersGalaxy ClustersCluster redshift surveys measure

• cluster mass, redshift, and spatial clustering

Sensitivity to dark energy• volume-redshift relation• angular-diameter distance–redshift relation• growth rate of structure• amplitude of clustering

Problems:• cluster selection must be well understood• proxy for mass?• need photo-z’s

CMB WMAP 2/3 WMAP 5 yrPlanck Planck 4yr

Clusters AMISZA

APEXAMIBA

SPTACT

DES

SNePan-STARRSDES LSST

JDEMSDSS CFHTLSCSP

ATLASSKAFMOS WFMOS

SDSS

Lensing CFHTLSATLAS KIDS

DES, VISTAJDEMLSST SKA

Pan-STARRS

SUBARU

20202008

ESSENCE

XCS

DUNE

2010

BAO LSST

SDSSDLS

LAMOST

Hyper suprime

DES, VISTA,VIRUS

Pan-STARRSHyper suprime JDEM

What’s AheadWhat’s Ahead2015

Roger Davies

Conclusions: Two Sides to the StoryConclusions: Two Sides to the Story

1. Right-Hand Side: Dark energy• “constant” vacuum energy, i.e., • time varying vacuum energy, i.e., quintessence

2. Left-Hand Side • Modification of GR • Standard cosmological model (FLRW) not applicable

The expansion history of the universe is not described by the Einstein-de Sitter model.

Explanations:

1. Well established: Supernova Ia2. Circumstantial: subtraction, age, structure formation, …3. Emergent techniques: baryon acoustic oscillations, clusters, weak lensing

Phenomenology:1. Measure evolution of expansion rate: is w ?2. Order of magnitude improvement feasible

Accelerators in the Universe March 2008Accelerators in the Universe March 2008Rocky Kolb University of ChicagoRocky Kolb University of Chicago

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Accelerators in the Universe March 2008 Rocky Kolb University of Chicago Accelerators in the Universe March 2008 Rocky Kolb University of Chicago