Sound velocity effects on the phase transition gravitational wave spectrum in the sound shell model

Abstract

A cosmological first-order phase transition gravitational wave could provide a novel approach to studying the early Universe. In most cases, the acoustic gravitational wave from the sound wave mechanism is dominant. Considering different sound velocities in symmetric and broken phases, we study sound velocity effects on the acoustic phase transition gravitational wave spectra in the sound shell model. We demonstrate that different sound velocities could obviously modify the peak frequency and peak amplitude of the gravitational wave power spectra. Therefore, taking more realistic sound velocities might provide more accurate predictions for various gravitational wave experiments.