The dark universe

P. Binétruy

AstroParticule et Cosmologie, Paris

Second Sino-French Workshop, Beijing, 28 August 2006

The twentieth century legacy

Two very successful theories :

• General relativity

A single equation, Einstein’s equation, successfully predicts tiny deviations from classical physics and describes the universe at large as well as its evolution.

R - (R/2) g = 8GN T

geometry matterQuickTime™ et un

décompresseur Cinepaksont requis pour visionner cette image.

Describes nature at the level of the molecule, the atom, the nucleus,the nucleons, the quarks and the electrons .

• Quantum theory

Difficult to reconcile general relativity with the quantum theory: bestillustration is the vacuum problem ( cosmological constant pb)

Classically, the energy of the fundamental state (vacuum) is not measurable. Only differences of energy are (e.g. Casimir effect).

Einstein equations: R - R g/2 = 8G T

geometry energy

Hence geometry may provide a way to measure absolute energies i.e. vacuum energy:

R - R g/2 = 8G T + 8G < T >

vacuum energy

similar to the cosmological term introduced by Einstein :

R - R g/2 = 8G T + g

Such a term tends to accelerate the expansion of the universe :

H2 = 8 G ( + ) /3 - k/a2 / (8 G )

curvature term

Present observations (k=0, < ) yield ~ H02 / 8 G

~ (10-3 eV)4

Computing the vacuum energy associated with the SM

vac ~ MW4 ~ (1011 eV)4 to be compared with ~ (10-3 eV)4

The electroweak scale MW ( lW = 10-18 m)

or the Planck scale mP = √ hc/8GN = 2.4 1018 GeV ( lP = 10-34 m)

obviously do not provide the size of the Universe.

Horizon scale : H0 -1 =1026 m

Critical energy density c = 3H02 /8 GN c

4

c = 10-3 eV

From the experimental and observational point of view,

• exploration of the infinitely small

electron, neutrino; up and downquarks make the proton/neutron

Why do we need a muon?

• exploration of the infinitely large

First only detecting visible light, then all electromagnetic spectrum

But also particles…

Cosmic rays

Neutrinos

And other types of waves … gravitational waves

Also indirect ways allow to identify new components of the Universe

First example: rotation curves of galaxies dark matter

e.g. spiral galaxies

astro-ph/9506004

Also indirect ways allow to detect new components of the Universe

First example: rotation curves of galaxies dark matter

luminous matter

e.g. spiral galaxies

astro-ph/9506004

Also indirect ways allow to detect new components of the Universe

First example: rotation curves of galaxies dark matter

luminous matter

exponential halo

e.g. spiral galaxies

astro-ph/9506004

Also indirect ways allow to detect new components of the Universe

First example: rotation curves of galaxies dark matter

luminous matter

exponential halo

total contribution

e.g. spiral galaxies

astro-ph/9506004

also detected through gravitational lensing

Second example: measuring cosmic distances with supernovae explosions dark energy

• Supernovae of type Ia

magnitude versus redshift

mB = 5 log(H0dL) + M - 5 log H0 + 25

luminosity distance dL = lH0 z ( 1 + ------- z + …)1-q0

2

q0 deceleration parameter q0 = M /2 - for a -CDM model

M M / c / c

Unknown component of equation of state p = w , w < 0

(cosmological constant w= -1)

Need for dark matter from the study of the universe at cosmological distance scales

Why are we so excited about this field?

Theoretical ideas

Experiments and observations

Theoretical ideas

Theories beyond the Standard Model provide many new fields :

Dark matter New fermions or vector fields

Dark energy New scalar fields

We have a good candidate for the unification of gravity with quantum theory : string theory.

Modifies drastically our view of spacetime : hopes to solvethe vacuum energy problem . But no clear solution in view!

Models for dark matter

Dark matter Modification of gravity

MOND TeVeSbaryonic non-baryonic

Clumped Hydrogen

dustMACHO

Primordial Black holes

Exotic particles

Extradimensions

thermal nonthermal

Light WIMPS SuperWIMPS axion Wimpzillas

Experiments and observations

• present

Acoustic series in P(k) becomes a single peak in (r)

Pure CDM model has no peak.

mh2 = 0.12

mh2 = 0.13

mh2 = 0.14

CDM with baryons is a good fit: 2 = 16.1 with 17 dof.Pure CDM rejected at 2 = 11.7

Baryon Acoustic OscillationsAcoustic oscillations are seen in the CMB . Look for the the same waves in the galaxy correlations.

M

= 0.88, v=0.12, H

0 = 46

SNe ignored.cannot accommodate with baryon acoustic peak.

CDM

Baryon oscillations are really discriminating for dark energy

Blanchard, Douspis, Rowan-Robinson, Sarkar 2005

Blanchard et al 2003

w=-1

Tot=1

BAO: Baryon Acoustic Oscillations(Eisenstein et al 2005, SDSS)

68.3, 95.5 et 99.7% CL

Confidence Contours

See R. Pain’s talk

DE

(z)

• future

Dark matter

See G. Gerbier’s talk

Indirect detection

Through annihilation of wimps accumulated in the center of massive objects : Earth, Sun, galactic center.

HESS, GLAST, AMS, ANTARES/AMANDA/KM3NET, ….

Energy (keV)500 505 515510 520 525

Inte

nsity

(10

-4 p

hoto

n cm

-2 s

-1 s

r-1)

0,0

0.5

2.5

1.5

3.0

-0.5

1.0

2.0

3.5

Position:FWHM:

511.06 ± 0.18 keV2.95 ± 0.5 keV

Are we heading for surprises?G

alac

tic la

titud

e (d

egre

es)

20

10

0

-20

-10

FWHM: 9° (-3° / +7°)

200

Difficult to understand if :

• Decay of massive particles

• Positrons injected by compact jet sources

• + decay of radioactive nuclei released by novae• + decay of 56Co released by thermonuclear (type Ia) supernovae

More adequate :• + decay of 56Co released by gravitational supernovae/hypernovae

• Annihilation of a new form of dark matter, scalar and light (Boehm, Hooper, Silk, Cassé & Paul, PRL 92, 101301)

The intensity of the 511 keV line emission (10-3 photons s-1) implies the annihilation

of ~1043 positrons per second in the Galactic bulge.

INTEGRAL/SPI spectrum of the Galactic center region

Dark energy

Future programs both in space (SNAP/JDEM/DUNE)and on the ground (SDSS, LSST, SKA/FAST,…)

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Expected Planck performance on dark energy equation of state

Huterer & Turner 2001

Seo & Eisenstein 2003w = w0 + w1 z

Other standard candles

Gamma ray bursts

coalescence of supermassive black holes

Determine the luminosity through a relation between the collimation corrected energy E and the peak energy

cf. SVOM/ECLAIRs

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Inspiral phase

Key parameter : chirp mass M = (m1 m2)3/5

(m1 + m2)1/5(z) (1+z)

Inspiral phase

Key parameter : chirp mass M = (m1 m2)3/5

(m1 + m2)1/5

Amplitude of the gravitational wave:

h(t) = F (angles) cos (t) M(z)5/3 f(t)2/3

dL

Luminosity distance

frequency f(t) = d/2dt

(z) (1+z)

Inspiral phase

Key parameter : chirp mass M = (m1 m2)3/5

(m1 + m2)1/5

Amplitude of the gravitational wave:

h(t) = F (angles) cos (t) M(z)5/3 f(t)2/3

dL

Luminosity distance poorly known in the case of LISA

~ 10 arcmin 1 HzSNR fGW

(z) (1+z)

z = 1 , m1 = 105 M, m2 = 6.105 M

(arcminutes)

dL/dL

3°

5%

Holz & Hughes

Using the electromagnetic counterpart

Allows both a measure of the direction and of the redshift

Limited by weak gravitational lensing?

Holz and HughesdL/dL

0.5%

My own theoretical prejudices :

• dark energy : back reaction models

• dark matter: WIMP connected with the electroweak symmetry breaking issue

Connecting the naturalness of the electroweak scale with the existence of WIMPs

STEP 1 : naturalness

mh2 = t

2 - g2 - h

23mt

2

22v2

6MW2 + 3MZ

2

8 2v2

3mh2

8 2v2

Naturalness condition : |mh2 | < mh

2

v = 250 GeV

Introduce new physics at t or raise mh to 400 GeV range

STEP 2 : stable particles in the MEW mass range

E

New local symmetry

New discrete symmetry

Standard Modelfermions

New fields

Lightest odd-parityparticle (LOP) is stable

Example 1: low energy SUSY

E

R symmetry

R parity

Standard Modelfermions

Supersymmetricpartners

Stable LSP

Example 2: extra compact dimension (orbifold)

E

5-dimensionalLorentz invariance

KK parity

Standard Modelfermions

KK modes

Stable lightestKK mode (B(1))

A(m) + B(n) C(p) + D(q)

m+n=p+q

(-)n

Example 3: Inert Doublet Model

E

?

H2 -H2

Standard Modelfermions

Inert scalars

Stable LightestInert Particle

Introduce a second Higgs doublet H2

which is not coupled to fermions (symmetry H2 -H2)

Barbieri, Hall, Rychkov, hep-ph/0603188

STEP 3 : compute relic density

LOP h02 ~

109 GeV-1 xf

g*1/2 MP < ann v >

25

Number of deg. of freedom at time of decoupling

LOP mass ~ MEW < ann v > ~ EW/MEW 2 LOP h02 ~ 1

to be compared with DM h02 = 0.112 0.009

mSUGRA

Co-annihilation 0

Near-resonant s-channel anni-hilation through heavy Higgs states A and H (b b, + -)

Focus point (WW,ZZ)

tan=5

tan=35

tan=50-

~

Y. Mambrini,, E. Nezri

STEP 4 : search for the LOP at LHC

As the LSP, missing energy signal

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STEP 5: search LOP through direct detection

e.g. minimal sugra model

Dark energy : back reaction models

The cosmological constant is small because the universe is old

cf. Dirac : large numbers should be considered as resultingfrom the evolution of the Universe. Applied to fundamental constants (but yields time variation difficult to reconcile with constaints)

The cosmological constant is (almost) cancelled by back-reaction effects on the expanding space.

Conclusion

A lively field where many fruitful collaborations maybe envisaged both on the theory and observational fronts

AstroParticule et Cosmologie

70 physicists, incl. 15 theorists60 engineers, technicians and supporting staff

High energy astrophysics

Cosmology

and gravitation

Neutrinos

Theory

Data analysis

R&D

Expérimental program @ APC 2002 2004 2006 2008 2010 2012

R&D Bolomètres , BRAIN CMBPOL ?

Planck

Supernovae CFHTLS

INTEGRAL

HESS

Superfaisceaux neutrinos

LISA

Borexino

Km3 Net

HESS-2

SNAP/JDEM/DUNE ?

Double Chooz

Mégatonne ?

SIMBOL X

X-shooter

SAMPAN

Antares

Auger Auger North

LISAPathfinder

SVOM / ECLAIRs