Transcript CMB: the genetic code of the Universe - uni

CMB as a physics laboratory
Recombination
T = 0.3 eV << me c2
Hydrogen is ionized
Thomson Scattering
Hydrogen is neutral
Cosmic
Dust
Point sources
Free free
Synchrot.
Tegmark, 2000



Microwave
Decoupling: photon mean free path,
l1/nesT > H-1.
Tdec=3000K 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 Tcmb=2.726K is then an
immediate indication that the values of Wtot
,Wb H0 we currently use are in the right
ballpark.
Background
CMB
z = 1100
History
1941
McKellar
1949
Gamow
1964
Penzias Wilson
1966
Sachs Wolfe
1970
Peebles Yu
1992
COBE
10-4
70
1999
Boomerang
10-5
20’
2002
DASI
2003
WMap
10-5
18’
2007
Planck
10-6
7’
CH,CN excitation
temperature in stars
Prediction Tcmb
10-1
DT/T grav.
DT/T Thomson
Polarization
Is the Universe….
Open, closed, flat, compact,
accelerated, decelerated,
initially gaussian, scale invariant,
adiabatic, isocurvature,
einsteinian…?
Ask the CMB….
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Geometry
Dynamics
Initial conditions
Growth of
fluctuations
What do we expect to find on the
CMB?
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Wo ,WL,W b ,n R,NR ,H0
ns, nt , s8
inflation pot. V (f)
W f,wf,b
VEP
topological defects
bouncing universe
Compact topology
Extra dimensions
the standard
XXXXX universe
boring
the XXXXXXX
unexpected universe
exciting
very exciting
the XXXX
weird
universe
Perturbing the CMB
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Observable: radiation intensity per unit frequency per polarization
state at each point in sky:
DT, D P, D E(n)
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In a homogeneous universe, the CMB is the same perfect black-body in
every direction
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In a inhomogenous universe, the CMB can vary in:
intensity
Grav. Pot, Doppler, intrinsic
fluctuations
DT
polarization
anisotropic scattering, grav.
waves
DP
spectrum
energy injection z<106
DE
Predicting the CMB
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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 z=1100 around the
observer
Complicate but linear !
Fluctuation spectrum
From DT/T
To Cl
Large
scales
Small
scales
Temperature fluctuations
Archaic
(>horizon scale)
Middle Age
Contemporary
(<damping scale)
 > 20
l < 100
20 <  <10’
 < 10’
100 < l < 1000 l > 1000
z>>1000
1000>z>10
z<10
Archaic CMB
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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)
Sachs-Wolfe effect
Last Scatt. Surface
F
z=0
SW
z = 1100
ISW
.
F
Fluctuation spectrum
Spherical
harmonic
expansion
DT
( ,  )   a m Ym ( ,  )
T
m
DT

am  
( ,  )Ym ( ,  )dW
T
2
C   ( a m ) 2



 DT 
 

 T  m
Sachs-Wolfe effect
Sachs - Wolfe
DT

T
3
Poisson in k - space :
Data: Cobe +Boomerang
3 2
k 2   -4a 2  (a ) k (a )  - H o W m (a ) k (a )a 2
2
Spectrum :
 DT  2
4 2
2 2
 
 G ( k ,  )dk  H o W m (a ) dk k (a ) j ( k d )
 T k
Harrison - Zeldovich
C
SW
P ( k )   k (a ) 2  Ak
4
C SW  
AH 0
4(  1)
P(k)=Akn
Integrated Sachs-Wolfe effect
Spectrum :
C
ISW

d  DT  2
  dkG ( k ,  ) 
 dt 
dt  T  k
d 2
H o  dk  dtj ( k ) (W m (a ) k (a ) 2 a 2 )
dt
4
2
Middle age CMB
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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 !
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
cs  c / 3
Therefore they propagated for
170,000lyr  0.05 Mpc
(almost) independently of cosmology.
Acoustic oscillations
LSS
z=0
z = 1100
Coupled fluctuations
D. Eisenstein
Acoustic oscillations
First peak: Sound horizon
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angular size : sensitive to the dominant
components
amplitude : sensitive to the baryon
component
Sound horizon
ds 2  0
FRW
dr 2
c dt  a ( t )
1 - kr 2
distance
2
2
2
rD  H 0
-1
 zd dz 
S c 
,

0
E(z) 

 W k -1 / 2 sin( W k

S( x)  
x
 W -1 / 2 sinh( W
k
 k
sound horizon
rSH  H 0
-1


dz 
S c s 
zd E ( z ) 


 SH 
R SH
 1 deg
RD
 SH 

 SH
R SH
H  H 0 E(z)
1/ 2
x)
k 1
k 0
1/ 2
x)
k  -1
 SH
RD
Acoustic peaks
Data: Boomerang 1999
Contemporary CMB
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Processes along the line-of-sight:
SZ effect: inverse Compton scattering
(cluster masses)
stochastic lensing ( mass fluctuation
power)
reionization ( epoch of first light)
Weak Lensing in CMB
Temperature field
Lensed temperature field
Hu 2002
How is polarization generated?
Thomson Scattering
Density pert.
&
Gravity Waves
Gravity
Waves
CMB
in 1999…
…2001
…2003
Sensitivity
Now
Map, 2003
Planck, 2007
Hu, 2002
The geometric effect
The kinematic effect
r(z)  
dz'
H ( z' )