Density and Graviton Perturbations in the Cosmic Microwave Background

Abstract

This paper evaluates and compares the gravitational wave and density perturbation contributions to the cosmic microwave background radiation, on the basis of the same power law inflationary model. The inflation to radiation transition is treated as instantaneous, but a model is constructed to allow for a smooth transition from the radiation to the matter dominated eras. The equations are numerically investigated and integrated, without any basic approximations being made. Use is made of the synchronous gauge, with appropriate gauge invariant variables, thus eliminating any confusion arising from unphysical gauge modes. We find a non- negligible gravitational wave contribution, which becomes dominant for a power law expansion with exponent $q < 13$. We also explore the dependence of our results with the main characteristic of the transition region, its length.