COSMIC MICROWAVE BACKGROUND OVERVIEW

The goal of cosmic microwave background (CMB) and large scale structur e (LSS) research is to determine the cosmological parameters that defi ne how structure arose in the universe. These include: early universe parameters associated with fluctuation generation, such as their stati stics, the amplitude and shape of primordial power spectra, and the to pology of space to the extent that this is accessible; the densities o f the various species present, baryons, cold and hot dark matter, the vacuum, as well as the overall mean curvature of space. Current CMB an d LSS data provide strong support for the gravitational instability th eory, rule out cosmic explosions as a dominant source of LSS,suggest t hat there was a long period in which hydrogen was recombined between t he redshift of photon decoupling and re-ionization associated with ear ly object formation, and are consistent with inflation-based expectati ons. For example, for inflation-based Gaussian fluctuations in a tilte d Lambda CDM sequence, the slope of the initial spectrum is within abo ut 5% of the (preferred) scale invariant form both when just the CMB d ata are used, and when it is combined with LSS data; with both, a nonz ero value of Omega(Lambda) is strongly preferred. The corresponding oC DM tilted open sequence prefers Omega(tot) < 1, but is overall less li kely than the flat Omega(Lambda) not equal 0 sequence. Forecasts of fu ture balloon and satellite experiments predict percent-level accuracy will be attainable among a large fraction of the 10 + parameters chara cterizing the cosmic structure formation theory.