Structure Formation in the Opaque Universe

Abstract

In the next two chapters we shall proceed down the other side of the cosmic loop and consider the history of perturbations down to the formation of the large-scale structure in the universe. We have convinced ourselves that the fluctuations of interest are residue of inflation. During inflation, all pre-inflationary inhomogeneities are suppressed except for the zero-point fluctuations. It is the zero-point fluctuations of the inflaton field that generate density perturbations, and the zero-point fluctuations of the metric field that generate primordial gravitational waves. In verifying that the structures seeded during inflation determine the fluctuations in the microwave background and the correlations in the distribution of galaxies and clusters of galaxies, we close the cosmic loop, and the story of inflation acquires a second leg to stand on.