The spectrum of gravitational waves in an f(R) model with a bounce

TL;DR

This paper explores a cosmological model with a bounce and modified gravity, analyzing its unique gravitational wave spectrum features, especially oscillations at low frequencies, using Bogoliubov coefficients.

Contribution

It introduces a bounce-inflation model within f(R) gravity and analyzes its gravitational wave spectrum, highlighting distinctive low-frequency oscillatory signals.

Findings

Distinctive oscillatory signals in the gravitational wave spectrum at low frequencies

Modified gravity influences only the early universe stages

Potential observational signatures of the bounce scenario

Abstract

We present an inflationary model preceded by a bounce in a metric $f(R)$ theory. In this model, modified gravity affects only the early stages of the universe. We analyse the predicted spectrum of the gravitational waves in this scenario using the method of the Bogoliubov coefficients. We show that there are distinctive (oscillatory) signals on the spectrum for very low frequencies; i.e., corresponding to modes that are currently entering the horizon.