Updated predictions for gravitational waves produced in a strongly supercooled phase transition

TL;DR

This paper updates predictions for gravitational wave signals from a strongly supercooled phase transition in a specific particle physics model, considering new factors like bubble wall friction and matter-dominated eras, with implications for detection by various observatories.

Contribution

It introduces revised estimates for GW signals from a conformal U(1)$_{B-L}$ model, including effects of bubble wall friction and matter domination, expanding the understanding of detectable signatures.

Findings

Strong bubble collision signals in parameter space

Characteristic tilted 'plateau' in GW spectrum due to matter era

Detectability of signals by LISA, AION/MAGIS, AEDGE, LIGO, and ET

Abstract

We update predictions for the gravitational wave (GW) signal from a strongly supercooled phase transition in an illustrative classically conformal U(1)$_{B-L}$ model. We implement $\propto \gamma^2$ scaling of the friction on the bubble wall and update the estimates for the efficiency factors for GW production from bubble collisions and plasma-related sources. We take into account the fact that a small decay rate of the symmetry-breaking field may lead to brief matter-dominated era after the transition, as the field oscillates around its minimum before decaying. We find that a strong bubble collision signal occurs in a significant part of the parameter space, and that the modified redshift of the modes that re-enter the horizon during the matter-dominated period generates a characteristic tilted `plateau' in the spectrum. The GW spectrum in this model would be detectable in the low-frequency range, e.g., by LISA, and in the mid-frequency range, e.g., by AION/MAGIS and AEDGE, and in the high-frequency range by LIGO and ET. The peak frequency of the signal is limited from below by collider constraints on the mass of the U(1)$_{B-L}$ gauge boson, while at high frequencies the slow decay of the scalar field and the resulting matter-dominated era diminishes the GW signal.