Gravitational Waves from Abelian Gauge Fields and Cosmic Strings at Preheating

TL;DR

This paper develops methods to analyze gravitational wave production from gauge fields and cosmic strings during preheating after hybrid inflation, revealing characteristic spectral features linked to topological defects.

Contribution

It introduces new theoretical and numerical techniques to study gravitational waves from gauge fields and cosmic strings at preheating, highlighting spectral signatures of topological structures.

Findings

Identification of new peaks in gravitational wave spectra related to mass scales.

Correlation of spectral features with string-like configurations and topological winding.

Observation of the evolution and decay of cosmic strings affecting gravitational wave signals.

Abstract

Primordial gravitational waves provide a very important stochastic background that could be detected soon with interferometric gravitational wave antennas or indirectly via the induced patterns in the polarization anisotropies of the cosmic microwave background. The detection of these waves will open a new window into the early Universe, and therefore it is important to characterize in detail all possible sources of primordial gravitational waves. In this paper we develop theoretical and numerical methods to study the production of gravitational waves from out-of-equilibrium gauge fields at preheating. We then consider models of preheating after hybrid inflation, where the symmetry breaking field is charged under a local U(1) symmetry. We analyze in detail the dynamics of the system in both momentum and configuration space, and show that gauge fields leave specific imprints in the resulting gravitational wave spectra, mainly through the appearence of new peaks at characteristic frequencies that are related to the mass scales in the problem. We also show how these new features in the spectra correlate with string-like spatial configurations in both the Higgs and gauge fields that arise due to the appearance of topological winding numbers of the Higgs around Nielsen-Olesen strings. We study in detail the time evolution of the spectrum of gauge fields and gravitational waves as these strings evolve and decay before entering a turbulent regime where the gravitational wave energy density saturates.