0 v 1 1 0 M ar 1 99 8 Cosmology in a nutshell + an argument against Ω Λ = 0 based on the inconsistency of the CMB and supernovae results

I present several simple figures to illustrate cosmology and structure formation in a nutshell. Then I discuss the following argument: if we assume that ΩΛ = 0 then the CMB results favor high Ωm while the supernova results favor low Ωm. This large inconsistency is strong evidence for the incorrectness of the ΩΛ = 0 assumption. Finally I discuss recent CMB results on the slope and normalization of the primordial power spectrum. 1 Cosmology in a nutshell The Big Bang model became the standard cosmological model soon after the discovery of the cosmic microwave background (CMB). The Big Bang model has a hot, dense early epoch (see Figure 1) when nucleosynthesis occurred. It also has an opaque surface that can naturally produce the Planckian spectrum of the CMB. The Steady State universe was not hotter in the past, has no epoch of Steady State Nucleosynthesis and has no opaque surface to produce the CMB. Gravitational collapse is the leading model of structure formation (Figure 2). Slight over-densities are gravitationally unstable and collapse under their own self-gravity. In an alternative family of models, structure forms from topological defects. In gravitational collapse models CMB anisotropies larger than ∼ 1 degree are acausal and rely on inflation to explain their existence. In defect models these large anisotropies are close by, causal and sub-horizon sized. 2 Charles H. Lineweaver Figure 1. Big Bang vs Steady State. Expanding horizon volumes in the Big Bang (A) and Steady State (B) models. The dots represent the density of the Universe. At early times only the Big Bang model was dense and hot providing an oven for nucleosynthesis and later an opaque surface of last scattering which naturally produces the Planckian spectrum of the CMB. . .. . . . . . . . .. . . . . .. . . . .. . . . . . . . . . . . . . . . . . .. . . . . . . . .. . . . . .. . . . .. . . . . . . . . . . . . . .