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The Cosmic Microwave Background

The Cosmic Microwave Background. Lecture 1 Elena Pierpaoli . (Cosmic Microwave Background). Brief History of time. Properties: isotropy and anisotropies. The CMB radiation is isotropic We are moving with respect to the CMB rest frame

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The Cosmic Microwave Background

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  1. The Cosmic Microwave Background Lecture 1 Elena Pierpaoli

  2. (Cosmic Microwave Background) Brief History of time

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

  4. Space Missions • PLANCK: • Smaller beam • Lower noise • Polarization • Better frequency coverage

  5. 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

  6. The power spectrum Nolta et al 08

  7. The decomposition of the CMB spectrum Challinor 04

  8. Evolution equations Photons Cold dark amtter Baryons metric Massive neutrinos Massless neutrinos

  9. Evolution of fluctuations Ma & Bertschinger 95

  10. Line of sight approach Seljak & Zaldarriaga 06

  11. Polarization Due to parity symmetry of the density field, scalar perturbations Have U=0, and hence only produce E modes.

  12. Scattering and polarization 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.

  13. Tensor modes Parity and rotation symmetry are no longer satisfied. B modes could be generated, along with T and E.

  14. The tensor modes expansion Scattering only produces E modes, B Are produced through coupling with E And free streaming.

  15. Power spectra for scalar and tensor perturbations Tensor to scalar ratio r=1

  16. Effect of parameters • Effect of various parameters on the T and P spectrum

  17. 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) 1)Neutrino mass: Physical effects on fluctuations on expansion • change the expansion rate • Change matter-radiation equivalence (but not recombination)

  18. Expan. factor a Matter dominated Radiation dominated Recombination 2) The relativistic energy density Nn 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)

  19. Neutrino species Bell, Pierpaoli, Sigurdson 06

  20. Neutrino interactions

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