Stable bounce and inflation in non-local higher derivative cosmology

TL;DR

This paper explores how non-local higher-derivative gravity models can resolve the Big Bang singularity with a non-singular bounce, ensuring stable inflationary evolution and perturbations free from pathologies.

Contribution

It demonstrates that ghost-free non-local gravity models provide a UV-complete inflationary scenario with a non-singular bounce and stable perturbations.

Findings

Non-local gravity models resolve the Big Bang singularity.

Inflationary trajectories are UV-complete and non-singular.

Perturbations remain stable without pathologies.

Abstract

One of the greatest problems of primordial inflation is that the inflationary space-time is past-incomplete. This is mainly because Einstein's GR suffers from a space-like Big Bang singularity. It has recently been shown that ghost-free, non-local higher-derivative ultra-violet modifications of Einstein's gravity may be able to resolve the cosmological Big Bang singularity via a non-singular bounce. Within the framework of such non-local cosmological models, we are going to study both sub- and super-Hubble perturbations around an inflationary trajectory which is preceded by the Big Bounce in the past, and demonstrate that the inflationary trajectory has an ultra-violet completion and that perturbations do not suffer from any pathologies.