1、Cosmic Microwave Background,Carlo Baccigalupi, SISSACMB lectures at TRR33, see the complete program at darkuniverse.uni-hd.de/view/Main/WinterSchoolLecture5These lectures are available in pdf format at people.sissa.it/bacci/work/lectures,CMB observables,Outline,Generalities and historical remarksCos
2、mological fossilsTotal intensity and polarization: T, E, BAngular power spectraStatus of the CMB observationsSuggested lectures,Generalities and historical remarks,Expanding universe CMB,compression in the early stages of an expanding universe causes lots of radiation arising from thermonuclear expl
3、osionsReactions are rapid enough to achieve thermalization and a black body spectrumIt is possible to compute the rarefaction caused by the expansion since that epochThe relic radiation is predicted to peak in microwaves, temperature of a few Kelvin, known today as the Cosmic Microwave Background (C
4、MB, Gamow et al. 1948),George Gamow, three years old in Odessa, Ukraine, 1907,Discovery,CMB: where and when?,Opacity: = (neT)-1 horizonDecoupling: horizonFree streaming: horizonCosmological expansion, Thomson cross section and electron abundance conspire to activate decoupling about 300000 years aft
5、er the Big Bang, at about 3000 K CMB photon temperature,A postcard from the big bang,From the Stephan Boltzmann law, regions at high temperature should carry high densityThe latter is activated by perturbations which are intrinsic of the fluid as well as of spacetimeThus, the maps of the CMB tempera
6、ture is a kind of snapshot of primordial cosmological perturbations,Animation from the NASA WMAP team,COsmic Background Explorer,From COBE to the Wilkinson Microwave Anisotropy Probe,About 20 years of insight into one of the most important observables in physicsLots of experiments, from ground as we
7、ll as the stratosphereA fantastic technological and data analysis progress, in parallel to theorylambda.gfsc.nasa.gov,Animation from the NASA WMAP team,Cosmological fossils,CMB physics: Boltzmann equation,d photons = metric + Compton scattering dt,d baryons+leptons = metric + Compton scattering dt,C
8、MB physics: Boltzmann equation,d neutrinos = metric + weak interaction dt,d dark matter = metric + weak interaction (?) dt,metric = photons + neutrinos + baryons + leptons + dark matter,CMB physics: metric,CMB Physics: Compton scattering,Compton scattering is anisotropicAn anisotropic incident inten
9、sity determines a linear polarization in the outgoing radiationAt decoupling that happens due to the finite width of last scattering and the cosmological local quadrupole,CMB anisotropy: total intensity,+,+,CMB anisotropy: polarization,+,+,+,Gradient (E):,Curl (B):,CMB anisotropy: reionization,e-,e-
10、,e-,CMB anisotropy: lensing,Last scattering,Forming structures - lenses,E,B,CMB anisotropy: lensing,Seljak & Zaldarriaga 1998,Forming structures - lenses,E,B,CMB anisotropy: lensing,acceleration,Last scattering,Anisotropies,T(,), Q(,), U(,), V(,),X=T,E,B,X(,)=lm almX Yslm(,),spherical harmonics,s=0
11、for T, 2 for Q and U,E and B modes have opposite parity,Angular power spectrum,T(,), Q(,), U(,), V(,),aXlm, X=T,E,B,Cl=m (almX)(almY)*/(2l+1),spherical harmonics,informationcompression,Status of the CMB observations and future experimental probes,CMB angular power spectrum,Angle 200/l degrees,CMB an
12、gular power spectrum,Angle 200/l degrees,Primordial power,Gravity waves,Acoustic oscillations,Reionization,Lensing,WMAP first year,Angle 200/l degrees,WMAP third year,Angle 200/l degrees,CMB angular power spectrum,boomerang,dasi,WMAP,Cosmological concordance model,Cosmological concordance model,Cosm
13、ological concordance model,CMB anisotropy statistics: unknown, probably still hidden by systematics,Evidence for North south asymmetry (Hansen et al. 2005)Evidence for Bianchi models (Jaffe et al. 2006)Poor constraints on inflation, the error is about 100 times the predicted deviations from Gaussian
14、ity (Komatsu et al. 2003)Lensing detection out of reach,Other cosmological backgrounds?,Neutrinos: abundance comparable to photons , decoupling at MeV , cold as photons , weak interaction Gravity waves: decoupling at Planck energy , abundance unknown , gravitational interaction Morale: insist with t
15、he CMB, still for many yearsthats the best we have for longSee lambda.gfsc.nasa.gov,Suggested reading,Modern Cosmology textbook from Scott DodelsonMy lecture notes from the course at SISSA, people.sissa.it/bacci/lectures/Cosmological inflation and large scale structure, textbook from Andrew R. Liddle and David H. LythThese lectures are available in pdf format at people.sissa.it/bacci/work/lectures/,
