The Future of the CMB

1. The Future of the CMB Marc Kamionkowski (Caltech) AIU ’08, Tsukuba, 13 March 2008

2. CMB that we see originates from edge of observable Universe as it was ~400,000 years after the big bang,~14 billion years ago You are here 14 billion light-years Causally connected region

3. Observe: • CMB smooth to 1st approximation • Has small fluctuations • BBN accounts for light-element abundances • Can infer: • Primordial density perturbations exist • Have small amplitude on largest scales • Have small amplitude on smallest scales • Have spectrum (in wavenumber k) no steeper than scale invariant

7. Slow-roll parameters

8. Inflationary perturbations:

10. (open) (flat) First test of inflation: Is the Universe flat? CMB determination of the geometry (MK, Spergel, and Sugiyama, 1994) T(n)=Σ almYlm(n) Cl=<|alm|2>

11. YES! 30 mK

12. BOOMERanG (2002)

13. Now even more precise from WMAP

14. Cosmological-parameter determination (Jungman, MK, Kosowsky, Spergel 1996)

16. WMAP-3: even better than we expected!!

17. WHAT NEXT???

18. STRUCTURE FORMATION GEOMETRY SMOOTHNESS INFLATION What is Einfl? STOCHASTIC GRAVITATIONAL WAVE BACKGROUND with amplitudeEinfl2

19. Detection of ultra-long-wavelength GWs from inflation: use plasma at CMB surface of last scatter as sphere of test masses.

20. Temperature pattern produced by one gravitational wave oriented in z direction z

21. No Gravity Waves

22. Gravity Waves

23. Detection of gravitational waves with CMB polarization (MK, Kosowsky, Stebbins, 1996; Seljak & Zaldarriaga 1996) “E Mode” Temperature map: Polarization Map: “B mode” Density perturbations have no handedness” so they cannot produce a polarization with a curl Gravitational waves do have a handedness, so they can (and do) produce a curl Model-independent probe of gravitational waves!

24. “Curl-free” polarization patterns “curl” patterns

25. Recall, GW amplitude is Einfl2l2 GWs T And from COBE, Einfl<3x1016 GeV GWs unique polarization pattern. Is it detectable? If E<<1015 GeV (e.g., if inflation from PQSB), then polarization far too small to ever be detected. But, if E~1015-16 GeV (i.e., if inflation has something to do with GUTs), then polarization signal is conceivably detectable by Planck or realistic post-Planck experiment!!!

26. Big news: If ns=0.95, and ε~η (and no weird cancellation), then ε~0.01, V~(2x1016 GeV)4, and r=T/S~0.1. I.e., GW background ~ “optimistic” estimates (e.g., Smith, Cooray,MK, arXiv:0802:1530)

27. WMAP BICEP QUIET1 QUEST (QUaD) Planck QUIET2 synchrotron 100 GHz synchrotron 100 GHz dust 100 GHz dust 100 GHz SPIDER Hivon

28. (Kesden, Cooray, MK 2002; Knox, Song 2002) If GW amplitude small, may need high-resolution T/P maps to disentangle cosmic-shear contribution to curl component from that due to inflationary gravitational waves.

31. Lensing shifts position on sky: Where the projected grav potential is

32. and so lensing induces a curl even if there was no primordial curl, withpower spectrum

34. How can we correct for it? T also lensed. In absence of lensing, but with lensing,

35. We can therefore reconstruct the deflectionangle….

38. Another possibility to correct for cosmic shear(Sigurdson, Cooray 2005) • Use 21-cm probes of hydrogen distribution to map mass distribution between here and z=1100

39. The CMB: What else is it good for?

40. WMAP-5: fraction of CMB photonsthat re-scattered after recombination (z~1100) is τ~0.1. If electrons that re-scattered these CMBCMB photons were ionized by radiationfrom the first stars, then the first starsformed at z=10

41. Probes of parity violation in CMB(Lue, Wang, MK 1999) Might new physics responsible for inflation be parity violating? TC and TG correlations in CMB are parity violating. Can be driven, e.g., by terms of form during inflation or since recombination WMAP search: Feng et al., astro-ph/0601095 Komsatsu et al. (WMAP-5)

42. GWs are tensor modes of perturbations. “Conventional” way to probe GWs: 1) low-l plateau versus peaks 2) B mode polarization High-frequency gravitational waves and the CMB New approach: Small scale GW behave as massless particles. They contribute to the energy density of the Universe.

43. Limits on gravitational-wave energy density Smith, Pierpaoli, MK (PRL, 2006)

44. Particle Decays and the CMBXuelei Chen and MK, PRD 70, 043502 (2004)L. Zhang et al., PRD 76, 061301 (2007)also, Kasuya, Kawasaki, Sugiyama (2004)and Pierpaoli (2004) • Can we constrain dark-matter decay channels and lifetimes from the CMB and elsewhere?

45. Photons absorbed by IGM Transparency window

46. IGM optical depth,temperature,and ionizationfor decaying particle

47. Ionization induced by particle Decays affects CMB power spectra

49. What Else?? Inflation predicts distribution of primordial density perturbations is Gaussian (e.g., Wang &MK, 2000). But how do we tell if primordial perturbations were Gaussian?? 

50. In single-field slow-roll inflation, nongaussianity parameter (e.g., Wang-MK 1999): fNL ~ ε (δρ/ρ) ~ 0.01 x 10-5 Will be small!! WMAP now at fNL ~50; Planck to getto fNL ~O(1). So simplest models not to be tested,but alternatives may produce largerfNL . Gaussian random field Φ=φ+fNL (φ2-<φ2>) Gravitational potential