Quasi-matter domination parameters in bouncing cosmologies

TL;DR

This paper introduces quasi-matter domination parameters for bouncing cosmologies, showing their role in describing perturbations and their duality with inflationary regimes, and compares theoretical predictions with PLANCK data.

Contribution

It defines new parameters for bouncing cosmologies that parallel slow-roll parameters in inflation, and demonstrates their effectiveness in matching observational data.

Findings

Spectral index and running parameter expressed in terms of the new parameters.

Duality between contracting matter-dominated and expanding quasi de Sitter phases.

Bouncing models fit well with PLANCK observational data.

Abstract

For bouncing cosmologies, a fine set of parameters is introduced in order to describe the nearly matter dominated phase, and which play the same role that the usual slow-roll parameters play in inflationary cosmology. It is shown that, as in the inflation case, the spectral index and the running parameter for scalar perturbations in bouncing cosmologies can be best expressed in terms of these small parameters. Further, they explicitly exhibit the duality which exists between a nearly matter dominated Universe in its contracting phase and the quasi de Sitter regime in the expanding one. The results obtained also confirm and extend the known evidence that the spectral index for a matter dominated Universe in the contracting phase is, in fact, the same as the spectral index for an exact Sitter regime in the expanding phase. Finally, in both the inflationary and the matter bounce scenarios, the theoretical values of the spectral index and of the running parameter are compared with their experimental counterparts, obtained from the most recent PLANCK data, with the result that the bouncing models here discussed do fit well accurate astronomical observations.