CMB as a physics laboratory

1
CMB as a physics laboratory
2
Recombination
T 0.3 eV ltlt me c2
Hydrogen is neutral
Hydrogen is ionized Thomson Scattering
3
Cosmic
Dust
Point sources
Free free
Synchrot.
Tegmark, 2000
4
Microwave
Decoupling photon mean free path, l1/nesT gt
H-1. Tdec3000K depends essentially only on
the baryon density (ne) and on the total matter
density (H-1 ). After 10Gyr, this has to cool
by a factor of roughly 1000 the present black
body spectrum at Tcmb2.726K is then an immediate
indication that the values of Wtot ,Wb H0 we
currently use are in the right ballpark.

5
Background
CMB
z 1100
6
History
1941 McKellar CH,CN excitation temperature in stars CH,CN excitation temperature in stars
1949 Gamow Prediction Tcmb Prediction Tcmb
1964 Penzias Wilson 10-1
1966 Sachs Wolfe DT/T grav. DT/T grav.
1970 Peebles Yu DT/T Thomson DT/T Thomson
1992 COBE 10-4 70
1999 Boomerang 10-5 20
2002 DASI Polarization Polarization
2003 WMap 10-5 18
2007 Planck 10-6 7
7
Is the Universe.

• Geometry
• Dynamics
• Initial conditions
• Growth of fluctuations

• Open, closed, flat, compact,
• accelerated, decelerated,
• initially gaussian, scale invariant,
• adiabatic, isocurvature,
• einsteinian?

Ask the CMB.
8
What do we expect to find on the CMB?

• Wo ,WL,W b ,n R,NR ,H0
• ns, nt , s8
• inflation pot. V (f)

the standard universe
XXXXX boring

• W f,wf,b
• VEP

the unexpected universe
XXXXXXX exciting

• topological defects
• bouncing universe
• Compact topology
• Extra dimensions

very exciting XXXX
the weird universe
9
Perturbing the CMB

• Observable radiation intensity per unit
  frequency per polarization state at each point in
  sky
• DT, D P, D E(n)
• In a homogeneous universe, the CMB is the same
  perfect black-body in every direction
• In a inhomogenous universe, the CMB can vary in

intensity Grav. Pot, Doppler, intrinsic fluctuations D T
polarization anisotropic scattering, grav. waves D P
spectrum energy injection zlt106 D E
10
Predicting the CMB

• General relativistic equations for baryons, dark
  matter, radiation, neutrinos,...
• Solve the perturbed, relativistic, coupled,
  Boltzmann equation
• Obtain the DT/T for all Fourier modes and at all
  times
• Convert to the DT/T on a sphere at z1100 around
  the observer

Complicate but linear !
11
Fluctuation spectrum
From DT/T
To Cl
Large scales
Small scales
12
Temperature fluctuations
Archaic (gthorizon scale) Middle Age Contemporary (ltdamping scale)
q gt 20 l lt 100 20 lt q lt10 100 lt l lt 1000 q lt 10 l gt 1000
zgtgt1000 1000gtzgt10 zlt10
13
Archaic CMB

• Sachs-Wolfe effect of superhorizon inflationary
  perturbations
• Integrated Sachs-Wolfe effect of subhorizon
  fluctuations when the gravitational potential is
  not constant (eg, nonflat metric, other
  components, non-linearity, etc)

14
Sachs-Wolfe effect
Last Scatt. Surface
F
z 0
SW
ISW
z 1100
.
F
15
Fluctuation spectrum
16
Sachs-Wolfe effect
Data Cobe Boomerang
P(k)Akn
17
Integrated Sachs-Wolfe effect
18
Middle age CMB

• Acoustic perturbations
• perturbations oscillate acoustically when their
  size is smaller than the sound horizon (the
  pressure wave has the time to cross the
  structure)
• The oscillations are coherent !

19
The sound horizon at decoupling

• The decoupling occurred 300,000 yrs after the big
  bang
• Acoustic perturbations in the photon-baryon
  plasma travelled at the sound speed
• Therefore they propagated for
• (almost) independently of cosmology.

20
Acoustic oscillations
LSS
z 0
z 1100
21
Coupled fluctuations
D. Eisenstein
22
Acoustic oscillations
23
First peak Sound horizon

• angular size sensitive to the dominant
  components
• amplitude sensitive to the baryon component

24
Sound horizon
25
Acoustic peaks
Data Boomerang 1999
26
Contemporary CMB

• Processes along the line-of-sight
• SZ effect inverse Compton scattering
  (?cluster masses)
• stochastic lensing (? mass fluctuation power)
• reionization (? epoch of first light)

27
Weak Lensing in CMB

Lensed temperature field
Temperature field
Hu 2002
28
How is polarization generated?
Thomson Scattering
29
Density pert. Gravity Waves
Gravity Waves
30
CMBin 1999
2001
2003
31
Sensitivity
Hu, 2002
Now
Map, 2003
Planck, 2007
32
The geometric effect
33
The kinematic effect