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

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.

Comments: V1: 8 pages. V2: 8 pages, some points clarified, typos corrected, some references added, final result unchanged. V3: 8 pages, title changed, presentation improved, discussion of phenomenological consequences added, comments very welcome. V4: Discussion further improved, comments very very welcome