Implications of Nano-Hertz Gravitational Waves on Electroweak Phase Transition in the Singlet Dark Matter Model

TL;DR

This paper investigates how nano-Hertz gravitational waves suggest a supercooled electroweak phase transition in a singlet dark matter model, impacting dark matter relic density and experimental constraints.

Contribution

It demonstrates that adjusting model parameters can lower the percolation temperature to 1 GeV, linking gravitational wave signals to dark matter and phase transition dynamics.

Findings

Percolation temperature can be lowered to 1 GeV.

Dark matter freeze-out can occur before the electroweak transition.

Entropy from the transition affects dark matter relic density.

Abstract

Inspired by the recent evidences of nano-Hertz stochastic gravitational waves observed by the pulsar timing array collaborations, we explore their implied supercooled electroweak phase transition in the singlet extension of the Standard Model. Our findings reveal that by adjusting the model parameter at per milli level, the corresponding percolation temperature can be continuously lowered to 1 GeV. With such a low percolation temperature, the singlet dark matter may freeze out before the electroweak phase transition, and, consequently, the entropy generated during the transition can significantly affect the dark matter relic density. It alleviates the tension between the requirement of a strong electroweak phase transition and the constraints imposed by dark matter direct detection, and can be tested in future experiments.