Gravitational waves from the vacuum decay with LISA

TL;DR

This paper compares gravitational wave spectra from vacuum decay models with and without gravity during a first-order phase transition, highlighting how LISA can distinguish between them based on amplitude differences.

Contribution

It introduces a numerical comparison of gravitational wave spectra from scalar field models with and without gravity, emphasizing the potential of LISA to differentiate these scenarios.

Findings

LISA can detect the gravitational wave spectrum from fast first-order phase transitions.

Differences in amplitude allow distinguishing models with and without gravity.

Numerical calculation of bubble wall velocity enhances understanding of the spectra.

Abstract

We investigate the gravitational wave spectrum resulted from the cosmological first-order phase transition. We compare two models; one is a scalar field model without gravitation, while the other is a scalar field model with gravitation. Based on the sensitivity curves of the LISA space-based interferometer on the stochastic gravitational-wave background, we compare the difference between the gravitational wave spectra of the former and the latter cases resulted from the bubble collision process. Especially, we calculated the speed of the bubble wall before collision for the two models numerically. We show that the difference between the amplitudes of those spectra can clearly distinguish between the two models. We expect that the LISA with Signal to Noise Ratio =10 could observe the spectrum as the fast first-order phase transition.