Observable Primordial Gravitational Waves from Cosmic Inflation

TL;DR

This paper reviews how inflation can produce primordial gravitational waves and explores scenarios like stiff periods after inflation that could amplify these waves to observable levels.

Contribution

It introduces mechanisms such as stiff periods and hyperkination that enhance primordial GWs, providing new pathways for their potential detection.

Findings

Primordial GWs can be amplified by stiff post-inflation periods.

Hybrid inflation with α-attractors can generate observable GWs.

Hyperkination in Palatini gravity enhances GW signals.

Abstract

I will review briefly how inflation is expected to generate a stochastic background of primordial gravitational waves (GWs). Then, I will discuss how such GWs can be enhanced by a stiff period following inflation, enough to be observable. I will present examples of this in the context of hybrid inflation with $\alpha$-attractors, or a period of hyperkination in Palatini gravity.