Inflation with a Weyl term, or ghosts at work

TL;DR

This paper investigates how adding a Weyl term to the inflationary action affects cosmological perturbations, revealing that vector modes become significant and scalar modes exhibit divergence in certain gauges, impacting ghost-related cosmology.

Contribution

It demonstrates the importance of vector perturbations and gauge-dependent behavior of scalar modes in inflation with a Weyl term, highlighting ghost effects in cosmology.

Findings

Vector perturbations become significant during inflation with a Weyl term.

Scalar modes diverge in the Newtonian gauge but are bounded in the comoving slicing.

The study emphasizes the role of ghosts in cosmological perturbation evolution.

Abstract

In order to assess the role of ghosts in cosmology, we study the evolution of linear cosmological perturbations during inflation when a Weyl term is added to the action. Our main result is that vector perturbations can no longer be ignored and that scalar modes diverge in the newtonian gauge but remain bounded in the comoving slicing.