Friedmann equations and cosmic bounce in a modified cosmological scenario

TL;DR

This paper derives modified cosmological equations from a quantum gravity-inspired thermodynamic model, proposing a universe that undergoes a bounce instead of a Big Bang singularity, with implications for early universe evolution.

Contribution

It introduces a phenomenological quantum gravity model leading to modified Friedmann equations and demonstrates a non-singular cosmic bounce.

Findings

Replaces Big Bang singularity with a regular bounce

Derives modified Raychaudhuri and Friedmann equations from thermodynamics

Suggests early universe evolution differs from standard cosmology

Abstract

In this work we present a derivation of modified Raychaudhuri and Friedmann equations from a phenomenological model of quantum gravity based on the thermodynamics of spacetime. Starting from general gravitational equations of motion which encode low-energy quantum gravity effects, we found its particular solution for homogenous and isotropic universes with standard matter content, obtaining a modified Raychaudhuri equation. Then, we imposed local energy conservation and used a perturbative treatment to derive a modified Friedmann equation. The modified evolution in the early universe we obtained suggests a replacement of the Big Bang singularity by a regular bounce. Lastly, we also briefly discuss the range of validity of the perturbative approach and its results.