Stochastic gravitational background from inflationary phase transitions

TL;DR

This paper studies how phase transitions during inflation produce gravitational waves with specific frequencies, potentially detectable by LIGO, and explores their implications for cosmic microwave background anisotropies.

Contribution

It analyzes the impact of inflationary phase transitions on gravitational wave signals and their observational signatures, linking early universe physics with current and future experiments.

Findings

Phase transitions can produce detectable gravitational wave peaks.

The epoch of phase transition influences the gravitational wave frequency.

CMB anisotropies provide insights into the parameters of inflationary models.

Abstract

We consider true vacuum bubbles generated in a first order phase transition occurring during the slow rolling era of a two field inflation: it is known that gravitational waves are produced by the collision of such bubbles. We find that the epoch of the phase transition strongly affects the characteristic peak frequency of the gravitational waves, causing an observationally interesting redshift in addition to the post-inflationary expansion. In particular it is found that a phase transition occurring typically 10$\div$20 $e-$foldings before the reheating at $kT\simeq 10^{15}$ GeV may be detected by the next Ligo gravity waves interferometers. Moreover, for recently proposed models capable of generating the observed large scale voids as remnants of the primordial bubbles (for which the characteristic wave lengths are several tens of Mpc), it is found that the level of anisotropy of the cosmic microwave background provides a deep insight upon the physical parameters of the effective Lagrangian.