Two-field cosmological phase transitions and gravitational waves in the singlet Majoron model

TL;DR

This paper investigates two-field cosmological phase transitions in the singlet Majoron model, revealing new transition patterns and calculating associated gravitational wave signals, which are generally undetectable by current space-based interferometers.

Contribution

It provides a comprehensive two-dimensional analysis of cosmological phase transitions and gravitational waves in the singlet Majoron model, uncovering novel transition patterns beyond single-field approximations.

Findings

Identified new two-field phase transition patterns.

Confirmed properties of phase transitions from previous studies.

Found gravitational wave signals are below current detector sensitivities.

Abstract

In the singlet Majoron model, we study cosmological phase transitions (PTs) and their resulting gravitational waves (GWs), in the two-field phase space, without freezing any of the field directions. We first calculate the effective potential, at one loop and at finite temperature, of the Standard Model Higgs doublet together with one extra Higgs singlet. We make use of the public available Python package CosmoTransitions to simulate the two-dimensional cosmological PTs and evaluate the gravitational waves generated by first-order PTs. With the full 2D simulation, we are able not only to confirm the PTs' properties previously discussed in the literature, but also we find new patterns, such as strong first-order PTs tunneling from a vacuum located on one axis to another vacuum located on the second axis. The two-field phase space analysis presents a richer panel of cosmological PT patterns compared to analysis with a single-field approximation. The PTGW amplitudes turn out to be out of the reach for the space-borne gravitational wave interferometers such as LISA, DECIGO, BBO, TAIJI and TianQin when constraints from colliders physics are taken into account.