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The Cosmic Microwave Background

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The Cosmic Microwave Background

Lecture 1

Elena Pierpaoli

(Cosmic Microwave Background)

Brief History of time

- The CMB radiation is isotropic
- We are moving with respect to the CMB rest frame
- There are tiny anisotropies, imprints of matter-radiation fluctuations.

- PLANCK:
- Smaller beam
- Lower noise
- Polarization
- Better frequency coverage

Observables

Measuring the Fundamental Properties of the Universe

Radiation

Matter

SDSS slice

CMB - Cosmic Microwave Background

(Temperature and Polarization)

DT(q,f) = S al,m Yl,m (q,f)

cl = Sm |al,m|2

d (x) = dr/r (x)

d (k) = FT[d (x)]

P(k) = < |d (k)|2>

Pgal(k) = b2 P(k)

bias

Nolta et al 08

Challinor 04

Photons

Cold dark amtter

Baryons

metric

Massive neutrinos

Massless neutrinos

Ma & Bertschinger 95

Seljak & Zaldarriaga 06

Due to parity symmetry of the density field, scalar perturbations

Have U=0, and hence only produce E modes.

If there is no U mode to start with, scattering does not generate it. No B mode is generated.

Scattering sources polarization through the quadrupole.

Parity and rotation symmetry are no longer satisfied.

B modes could be generated, along with T and E.

Scattering only produces E modes, B

Are produced through coupling with E

And free streaming.

Tensor to scalar ratio r=1

- Effect of various parameters on the T and P spectrum

Fluctuation on scale enters the horizon

Derelativization

Expan. factor a

Matter dominated

Radiation dominated

Neutrinos free-stream

heavy

Neutrinos do not free-stream

(I.e. behave like Cold Dark Matter)

light

Recombination

(T=0.25 eV)

on fluctuations

on expansion

- change the expansion rate
- Change matter-radiation equivalence (but not recombination)

Expan. factor a

Matter dominated

Radiation dominated

Recombination

Nn = (rrad - rg) / r1n

3

>3

- Effects:
- change the expansion rate
- Change matter-radiation equivalence (but not the radiation temperature, I.e. not recombination)

- Model for:
- neutrino asymmetry
- other relativistic particles
- Gravitational wave contribution
- (Smith, Pierpaoli, Kamionkowski 2006)

CONSTRAINTS:

Before WMAP: N <17

After WMAP:N< 6.6

(Pierpaoli MNRAS 2003)

Bell, Pierpaoli, Sigurdson 06