Entanglement entropy of cosmological perturbations for S-brane Ekpyrosis

TL;DR

This paper computes the entanglement entropy of scalar perturbations in a specific ekpyrotic cosmological model with an S-brane bounce, deriving bounds on the bounce energy scale based on entropy considerations.

Contribution

It introduces a calculation of entanglement entropy in a recent improved ekpyrosis model with an S-brane bounce, linking quantum information measures to cosmological parameters.

Findings

Entanglement entropy remains subdominant to thermal entropy during reheating.

Provides an upper bound on the bounce energy scale based on entropy constraints.

Demonstrates the role of gravitational non-linearities in cosmological perturbations.

Abstract

We calculate the entanglement entropy of scalar perturbations due to gravitational non-linearities present in any model of canonically-coupled, single-field ekpyrosis. Specifically, we focus on a recent model of improved ekpyrosis which is able to generate a scale-invariant power spectrum of curvature perturbations and gravitational waves as well as have a non-singular bounce due to an S-brane at the end of ekpyrotic contraction. By requiring that the entanglement entropy remians subdominant to the thermal entropy produced during reheating, we get an upper bound on the energy scale of the bounce.