Modifications in the Spectrum of Primordial Gravitational Waves Induced by Instantonic Fluctuations

TL;DR

This paper investigates how instantonic transitions and modifications to General Relativity, like the Holst term, alter the primordial gravitational wave spectrum and its potential observational signatures.

Contribution

It introduces a new form of the gravitational wave power spectrum accounting for instantonic effects and parity violation due to the Holst term in gravity.

Findings

Instantonic transitions modify the primordial gravitational wave spectrum.

The Holst term induces parity violation in the spectrum.

Potential experimental signatures of these modifications are outlined.

Abstract

Vacuum to vacuum instantonic transitions modify the power spectrum of primordial gravitational waves. We evaluate the new form of the power spectrum for ordinary gravity as well as the parity violation induced in the spectrum by a modification of General Relativity known as Holst term and we outline the possible experimental consequences.