On the Transfer of Adiabatic Fluctuations through a Nonsingular Cosmological Bounce

TL;DR

This paper investigates how cosmological perturbations transfer through a nonsingular bounce, finding that the growing mode persists across the bounce, which differs from previous singular matching approaches, impacting Ekpyrotic cosmology.

Contribution

It provides an exact calculation of fluctuation transfer through a nonsingular bounce, showing the continuity of the growing mode across the bounce.

Findings

Growing mode in contracting phase continues as growing mode in expanding phase.

Results differ from singular hypersurface matching methods.

Implications for Ekpyrotic cosmology when fluid equation of state is large.

Abstract

We study the transfer of cosmological perturbations through a nonsingular cosmological bounce in a special model in which the parameters of the bounce and the equation of state of matter are chosen such as to allow for an exact calculation of the evolution of the fluctuations. We find that the growing mode of the metric fluctuations in the contracting phase goes over into the growing mode in the expanding phase, a result which is different from what is obtained in analyses in which fluctuations are matched at a singular hypersurface. Consequences for Ekpyrotic cosmology are discussed in a limit when the equation of state of a fluid becomes large.