No-go theorem for inflation in Ricci-inverse gravity

TL;DR

This paper investigates Ricci-inverse gravity, a novel fourth-order gravity theory, finding that while inflationary solutions exist without singularities, they are unstable, leading to a no-go theorem for inflation in this model.

Contribution

It provides the first analysis of inflationary solutions in Ricci-inverse gravity and demonstrates their instability, establishing a no-go theorem for inflation in this framework.

Findings

Inflationary solutions are free from singularities.

Both isotropic and anisotropic inflation are unstable.

A no-go theorem for inflation in Ricci-inverse gravity is established.

Abstract

We study a recent proposed Ricci-inverse gravity, which is a very novel type of fourth-order gravity. In particular, we are able to figure out both isotropically and anisotropically inflating universes to this model. More interestingly, these solutions are free from a singularity problem. However, stability analysis based on the dynamical system method shows that both isotropic and anisotropic inflation of this model turn out to be unstable against field perturbations. This result implies a no-go theorem for both isotropic and anisotropic inflation in the Ricci-inverse gravity.