The rise of a tensor instability in Eddington-inspired gravity

TL;DR

This paper investigates tensor perturbations in an extended Eddington-inspired gravity model, revealing a linear instability in the tensor modes during the early universe, which significantly alters Einstein gravity predictions.

Contribution

It introduces an extension to Eddington's gravitational action and analyzes the resulting tensor instabilities in a cosmological setting.

Findings

Tensor modes are linearly unstable in the Eddington regime.

The instability leads to significant modifications to Einstein gravity.

The work highlights potential implications for early universe cosmology.

Abstract

In this work an extension to Eddington's gravitational action is analyzed. We consider the tensor perturbations of a FLRW space-time in the Eddington regime in where the tensor mode is linearly unstable deep and the resulting modifications to Einstein regime are quite strong.