The Cosmic Microwave Background & Inflation, Then & Now

Abstract

Boomerang, Maxima, DASI, CBI and VSA significantly increase the case for accelerated expansion in the early universe (the inflationary paradigm) and at the current epoch (dark energy dominance), especially when combined with data on high redshift supernovae (SN1) and large scale structure (LSS). There are ``7 pillars of Inflation'' that can be shown with the CMB probe, and at least 5, and possibly 6, of these have already been demonstrated in the CMB data: (1) a large scale gravitational potential; (2) acoustic peaks/dips; (3) damping due to shear viscosity; (4) a Gaussian (maximally random) distribution; (5) secondary anisotropies; (6) polarization. A 7th pillar, anisotropies induced by gravity wave quantum noise, could be too small. A minimal inflation parameter set, ω_b,ω_{cdm}, Ω_{tot}, Ω_Q,w_Q,n_s,τ_C, σ_8}, is used to illustrate the power of the current data. We find the CMB+LSS+SN1 data give Ω_{tot} =1.00^{+.07}_{-.03}, consistent with (non-baroque) inflation theory. Restricting to Ω_{tot}=1, we find a nearly scale invariant spectrum, n_s =0.97^{+.08}_{-.05}. The CDM density, Ω_{cdm}{\rm h}^2 =.12^{+.01}_{-.01}, and baryon density, Ω_b {\rm h}^2 = >.022^{+.003}_{-.002}, are in the expected range. (The Big Bang nucleosynthesis estimate is 0.019\pm 0.002.) Substantial dark (unclustered) energy is inferred, Ω_Q \approx 0.68 \pm 0.05, and CMB+LSS Ω_Q values are compatible with the independent SN1 estimates. The dark energy equation of state, crudely parameterized by a quintessence-field pressure-to-density ratio w_Q, is not well determined by CMB+LSS (w_Q < -0.4 at 95% CL), but when combined with SN1 the resulting w_Q < -0.7 limit is quite consistent with the w_Q=-1 cosmological constant case.

20 pages, 8 figures, in Theoretical Physics, MRST 2002: A Tribute to George Libbrandt (AIP), eds. V. Elias, R. Epp, R. Myers