Probing the Gravitational Wave Signature from Cosmic Phase Transitions at Different Scales

TL;DR

This paper proposes a method to distinguish gravitational waves from cosmic phase transitions and inflation by comparing signals in future gravitational wave detectors and the CMB, clarifying mode evolution calculations.

Contribution

It introduces a new signature based on the relative magnitude of gravitational wave spectra at different scales, enhancing the ability to identify their cosmic origin.

Findings

Identifies a distinguishable flat spectrum signature at direct detection frequencies.

Clarifies the impact of post-horizon-crossing evolution on mode calculations.

Provides a framework for discriminating gravitational wave sources in future observations.

Abstract

We present a new signature by which to one could potentially discriminate between a spectrum of gravitational radiation generated by a self-ordering scalar field vs that of inflation, specifically a comparison of the magnitude of a flat spectrum at frequencies probed by future direct detection experiments to the magnitude of a possible polarization signal in the Cosmic Microwave Background (CMB) radiation. In the process we clarify several issues related to the proper calculation of such modes, focusing on the effect of post-horizon-crossing evolution.