cosmic microwave background observables.pdf - The Dark Universe ...

Cosmic MicrowaveBackgroundCarlo Baccigalupi, , SISSACMB lectures at TRR33, see the complete program atdarkuniverse.uni-hd.de/view/Main/WinterSchoolLecture5These lectures are available in pdf format atpeople.sissa.it/~bacci/work/lectures

CMB observables

Outline‣ Generalities and historical remarks‣ Cosmological fossils‣ Total intensity and polarization: T, E, B‣ Angular power spectra‣ Status of the CMB observations‣ Suggested lectures

Generalities andhistorical remarks

A postcard from the big bang‣ From the StephanBoltzmann law, regions athigh temperature shouldcarry high density‣ The latter is activated byperturbations which areintrinsic of the fluid aswell as of spacetime‣ Thus, the maps of theCMB temperature is akind of snapshot ofprimordialcosmologicalperturbationsAnimation from the NASA WMAP team

COsmic Background Explorer

From COBE to the WilkinsonMicrowave Anisotropy Probe‣ About 20 years of insightinto one of the mostimportant observables inphysics‣ Lots of experiments,from ground as well asthe stratosphere‣ A fantastic technologicaland data analysisprogress, in parallel totheory‣ lambda.gfsc.nasa.govAnimation from the NASA WMAP team

Cosmological fossils

CMB physics: Boltzmann equationd photonsdt= metric + Compton scatteringd baryons+leptonsdt= metric + Compton scattering

CMB physics: metric

CMB Physics: Compton scattering‣ Compton scattering isanisotropic‣ An anisotropic incidentintensity determines alinear polarization in theoutgoing radiation‣ At decoupling thathappens due to the finitewidth of last scatteringand the cosmologicallocal quadrupolee -

CMB anisotropy: reionizatione - e -e -

CMB anisotropy: lensingE BForming structures - lensesLast scatteringSeljak & Zaldarriaga 1998

CMB anisotropy: lensingE BForming structures - lensesaccelerationLast scattering

AnisotropiesT(θ,φ), Q(θ,φ), U(θ,φ), V(θ,φ)sphericalharmonicsX(θ,φ)=Σ lm a lmX Y s lm (θ,φ)X=T,E,Bs=0 for T, 2 for Q and UE and B modes have opposite parity

Angular power spectrumT(θ,φ), Q(θ,φ), U(θ,φ), V(θ,φ)sphericalharmonicsa X lm , X=T,E,BinformationcompressionC l =Σ m [(a lmX )(a lmY )*]/(2l+1)

Status of the CMB observationsand future experimental probes

CMB angular power spectrumAngle ≈ 200/l degrees

CMB angular power spectrumAcoustic oscillationsPrimordial powerReionizationLensingAngle ≈ 200/l degreesGravity waves

WMAP first yearAngle ≈ 200/l degrees

WMAP third yearAngle ≈ 200/l degrees

CMB angular power spectrumboomerangWMAPdasi

Cosmological concordance model

Cosmological concordance model

Cosmological concordance model

CMB anisotropy statistics: unknown,probably still hidden by systematics‣ Evidence for North southasymmetry (Hansen et al.2005)‣ Evidence for Bianchimodels (Jaffe et al. 2006)‣ Poor constraints oninflation, the error isabout 100 times thepredicted deviations fromGaussianity (Komatsu etal. 2003)‣ Lensing detection out ofreach

Other cosmological backgrounds?‣ Neutrinos: abundance comparable tophotons ☺, , decoupling at MeV ☺, , cold asphotons , weak interaction ‣ Gravity waves: decoupling at Planckenergy ☺, , abundance unknown ,gravitational interaction ‣ Morale: insist with the CMB, still for manyyears…thatthat’s s the best we have for long…‣ See lambda.gfsc.nasa.gov

Suggested reading‣ Modern Cosmology textbook from ScottDodelson‣ My lecture notes from the course atSISSA, people.sissa.it/~bacci/lectures/‣ Cosmological inflation and large scalestructure, textbook from Andrew R. Liddleand David H. Lyth‣ These lectures are available in pdf formatat people.sissa.it/~bacci/work/lectures/