B.Sadoulet

Phys 250 -1 1

The Dark Side

The Dark Side of the Universe

LogisticsAn overview

A first taste without the sourness of equations!

Outline

B.Sadoulet

Phys 250 -1 2

The Dark Side

LogisticsBasic Information

Instructor: Professor Bernard Sadoulet (sadoulet@cfpa.berkeley.edu)Class Time: T/Th 9:40-11:00 Pacific TimeClass Location: 501 Campbell Hall UCB and on the InternetOffice Hours:

Immediately after class in 501 Campbell (Astronomy Dept Coffee)Thursday 2:00-3:00 301 LeConte or by phone (510 642 5719)Or by appointment

Credit (UCB)Requirements

regularly attend the lectures and read the assigned preparatory material problem sets approximately every three weeks a final paper on a topical aspect of the dark matter or dark energy problems

Outline due end of OctoberPaper due Dec 1

Other students and postdocs are welcomed (and encouraged) to submit problem setsand the final paper.

Should only represent medium load!

Books:None required (we will use recent articles on the web)P.J.E. Peebles “Principles of Physical Cosmology” (Princeton University Press, 1993)E.W. Kolb and M.S. Turner “The Early Universe” (Addison-Wesley, 1994)

B.Sadoulet

Phys 250 -1 3

The Dark Side

Style

As interactive as possibleYour own experienceLinkages and connections

Attempt to go beyondThe standard lore and current fashionThe maths or the complexity

Spirit of Awe

Looking beyond: Camille Flammarion

B.Sadoulet

Phys 250 -1 4

The Dark Side

Initial explosion!<= Expansion of the universe

Since Hubble (1925) we know that distant galaxiesare receding from each other

<= Universe was hot in the early timesWe detect the glow in cosmic microwave background

Initially at 3000K, now at 2.73K

The formation of deuterium, helium and lithium requires a hot furnace

The Big Bang

B.Sadoulet

Phys 250 -1 5

The Dark Side

Galaxies as Tracers ofSpace

Hubble Space TelescopeDeep Field

≈ 5 million galaxies/squared degree200 billion galaxies over whole sky

B.Sadoulet

Phys 250 -1 6

The Dark Side

Cosmic MicrowaveBackgroundCOBE

2.726 K!

B.Sadoulet

Phys 250 -1 7

The Dark Side

Primordial Nucleosynthesis

Not enough 4He producedto account for observed≈23% in mass

=> hot early universe(Gamov)

B.Sadoulet

Phys 250 -1 8

The Dark Side

From Quarks to the Cosmos

Big Bang enables influence of infinitely small oninfinitely large

B.Sadoulet

Phys 250 -1 9

The Dark Side

The Role of Gravity

Expansion is governed by gravitySlowed down by gravity

At least we thought so, till recently!

Define critical density ρc as the density at which the kineticenergy and potential energy are equal in magnitude

> 1 recollapses = closed universe= 1 expands forever, stops at infinity = flat universe< 1 expands forever = open universe

Ω < 1

Ω = 1

Ω > 1time

a(t) = scale parameter (e.g.,distance between two distant galaxies)

=c

How can we have gravitational repulsion?Generalization of Newton’s law to General Relativity

If pressure is negative, gravity can become repulsive!

aacceleration

=G

r2

mass density V → a

acceleration =

G

r 2

1

c2 uenergy density

+ 3 ppressure

GR gravitational mass1 2 4 4 4 3 4 4 4

Vr

a

V

B.Sadoulet

Phys 250 -1 10

The Dark Side

Cosmic MicrowaveBackground

Boomerang + Maxima: The universe is spatially flat!

B.Sadoulet

Phys 250 -1 11

The Dark Side

The Role of Gravity 2Formation of structure

Gravity is unstable!Local increase of density tends to grow:

attracts matter around it.This generates velocities on top of expansion.

We see these fluctuations in cosmic microwavebackground.

We can follow them as a function of timeA quantum origin?

=> We need to do a little bit of General RelativityTo describe expansion

Understand how we can extract both the energy density and the pressure

To understand the growth of structureVery sensitive also to the energy density and the pressureAlso a signature of the nature of dark matter

Extrapolationflat universe

at z≈1000

CDM

ν onlybaryonic

Large scalestructureCMB

B.Sadoulet

Phys 250 -1 12

The Dark Side

The Initial Seeds

Seen in Cosmic Microwave Backgrounde.g. Boomerang

B.Sadoulet

Phys 250 -1 13

The Dark Side

A Bizarre Universe

Not a mixture of matter and antimatter!The most obvious guess: equal mixture of matter and antimatterWe do not see the high energy photons from matter-antimatter annihilation

There is more than ordinary matter and photonsOrdinary matter = baryons + electrons

Primordial abundance of deuterium => Ωbaryon≈ 5%

In addition:Dark matter

Represents ≈85% of “matter” = “which clumps!” => Ωdark matter≈ 30%Dominates gravity and is responsible for the formation of structure

Dark energy ?Evidence for acceleration of the universe = “antigravity!”Diffuse and appeared “recently” => Ωdark energy≈ 65%

Cosmic microwave background: universe is flat => SUM ≈ 100%

The

Dar

k Si

de !

B.Sadoulet

Phys 250 -1 14

The Dark Side

Dark Matter

Solid evidence that 85% ofthe mass in the universe isdark

rotation curves in spiral galaxies

globular clusters / gas aroundelliptical galaxies

velocity dispersion in clustersX-ray gas in clustersgravitational lensing by clusters

Large scale flows

B.Sadoulet

Phys 250 -1 15

The Dark Side

What is the Nature of Dark Matter

A map of the territory

=> systematic effort

non baryonic

exotic particles

non-thermal

Axions Wimpzillas

baryonic

gas VMO

dust MACHOs

clumped H2?

Mirror branesEnergy in the bulk

PrimordialBlack Holes

?

thermal

Light Neutrinos WIMPs

dark matter

B.Sadoulet

Phys 250 -1 16

The Dark Side

Baryonic Dark Matter

MACHOs

Hot/Warm Diffuse Gas

B.Sadoulet

Phys 250 -1 17

The Dark Side

Non Baryonic Dark Matter

Many hints that the bulk of Dark Matter is non baryonic!

CandidatesLight massive neutrinosAxionsWeakly Interactive Massive Particles

Ωeff

Ho=65km/s/Mpc

0.001

0.01

0.1

1

10 100 1000 1e+04 1e+05 1e+06

Vel Corr.b=1

Shaya et al.

Voids

BaryonInvent.

Cluster Evol.

Potentb=1

Power spectrum

Dipoleb=1

Supernovae+ CMBR

CosmologicalTests

Primordial Nucleosynthesis

Tytler et al.

Scale (kpc)

B.Sadoulet

Phys 250 -1 18

The Dark Side

CDMS I

View down tunnel (Icebox at far end) Icebox inside Pb shielding

Detectors

Inner Pb shieldPolyethylene

Pb ShieldActive Veto

20mK

B.Sadoulet

Phys 250 -1 19

The Dark Side

Recent Controversy

DAMA claims tohave foundWIMPs

CDMS hascontradictoryresults

B.Sadoulet

Phys 250 -1 20

The Dark Side

The Dark Energy Revolution

Supernovae at high redshift

Before After Subtraction

A HST image

B.Sadoulet

Phys 250 -1 21

The Dark Side

Dark Energy

One type of supernovaeappears to have veryconstant light curves

(once corrected for decay time)

Distant supernovae appeardimmer than expected ina flat universe

Potential problemsAre supernova properties really

constant?Dust?

Thursday 8/31: discussedby Saul Perlmutter

time

Lum

inos

ity

Distance

m=1=0

Fai

nter

B.Sadoulet

Phys 250 -1 22

The Dark Side

Very surprising!

What can it be?• Vacuum energy <- fluctuation p =-u Einstein’s gravitational

constantRelated to the zero point energy of harmonic oscillator

Naïve calculation: too small by 10120!

• A new form of matter/energy: Quintessence p =wu w >-1

• Tangled topological defects

=> We have no clue!

Why now?Evolution rate depends on w!

u t( ) ≡ t( ) ∝ a t( )−3 1+ w( )

B.Sadoulet

Phys 250 -1 23

The Dark Side

The Grand SynthesisNot incompatible with rest of cosmology!

B.Sadoulet

Phys 250 -1 24

The Dark Side

Our territory

Why b m

Do we understand Gravity?

nonbaryonic

exotic particles

non-thermal

Axions Wimpzillas

baryonic

gas VMO

dust MACHOs

clumped H2?

Other dimensions?Primordial

Black Holes?

Quintessence

thermal

Light Neutrinos WIMPs

dark matter and energy

B.Sadoulet

Phys 250 -1 25

The Dark Side

Our ToolsInventoriesPattern and growth of structurePattern and growth of velocitiesMeasurement of pressure

Because

we can measure both the energy density and the pressure by measuring theexpansion as a function of time or the distance vs z

Laboratory searchesDark matterDark energy

We will emphasizeNew probes

CMBR, supernovae, weak lensing, Sunyaev-Zel’dovich, laboratory detection

New toolslarge field of view telescopes, adaptive optics, large format arrays, cryogenic

detectors

accacceleration =

G

r2

1

c2 uenergy density

+ 3 ppressure

GR gravitational mass1 2 4 4 4 3 4 4 4

V

a t( )expansion ⇔ d z( ) ⇐ 1+ z =

a to( )a t( )

t = cd

B.Sadoulet

Phys 250 -1 26

The Dark Side

Instrumentation

Enabling technologye.g. Cryogenic Detectors

B.Sadoulet

Phys 250 -1 27

The Dark Side

OutlineThe Current Paradigm

The Big Bang, Inflation and the homogeneity of the universe at large scale.General Relativity tools: Robertson Walker metric, Friedman equation.Spatial geometry and observations of the Cosmic Microwave BackgroundBaryon density: Baryogenesis and nucleosynthesis

Dark Matter: astrophysical observationsObservational evidence and inventoryThe pattern and growth of structure and velocitiesThe dark baryons: MACHOs and warm/hot diffuse baryons

Non Baryonic Dark Matter: the particle physics connectionEvidence for non baryonic natureTheoretical framework (QCD, supersymmetry, extra dimensions)Neutrino mass measurements Axion searches WIMP searches (Direct and indirect detection)

Dark Energy Observational evidence: high redshift supernovaeMeasuring pressure in the universe: distance versus redshiftWhat can be learnt from the growth of structure?Models for dark energy

Directions for progress