On the properties of the transition matrix in bouncing cosmologies

TL;DR

This paper analyzes how cosmological fluctuations evolve through a bounce, demonstrating their description via transmission, reflection, and an S-matrix, emphasizing time reversal invariance for a more robust understanding.

Contribution

It provides a new perspective on fluctuation evolution in bouncing cosmologies using S-matrix formalism and highlights their time reversal invariance.

Findings

Evolution described by transmission and reflection coefficients

Fluctuations behave in a time reversal invariant manner

Results are interpreted with a firmer theoretical basis

Abstract

We elaborate further on the evolution properties of cosmological fluctuations through a bounce. We show this evolution to be describable either by ``transmission'' and ``reflection'' coefficients or by an effective unitary S-matrix. We also show that they behave in a time reversal invariant way. Therefore, earlier results are now interpreted in a different perspective and put on a firmer basis.