Gravitational waves at aLIGO and vacuum stability with a scalar singlet extension of the Standard Model

TL;DR

This paper explores how a scalar singlet extension of the Standard Model can induce a first-order phase transition producing gravitational waves detectable by aLIGO, while also stabilizing the electroweak vacuum at high energy scales.

Contribution

It identifies parameter regions where a scalar singlet causes a first-order phase transition at high energies, producing observable gravitational waves and stabilizing the vacuum.

Findings

Gravitational waves from the phase transition may be detectable by aLIGO (O5).

The scalar singlet stabilizes the electroweak vacuum up to high scales.

Benchmark points show phase transition characteristics consistent with GW detection.

Abstract

A new gauge singlet scalar field can undergo a strongly first-order phase transition (PT) leading to gravitational waves (GW) potentially observable at aLIGO and simultaneously stabilize the electroweak vacuum. aLIGO (O5) is potentially sensitive to cosmological PTs at $10^7$-$10^8$ GeV, which coincides with the requirement that the singlet scale is less than the Standard Model (SM) vacuum instability scale, which is between $10^8$ GeV and $10^{14}$ GeV. After sampling its parameter space, we identify three benchmark points with a PT at about $T\approx 10^7$ GeV in a gauge singlet extension of the SM. We calculate the nucleation temperature, order parameter, characteristic timescale, and peak amplitude and frequency of GW from bubble collisions during the PT for the benchmarks and find that, in an optimistic scenario, GW from such a PT may be in reach of aLIGO (O5). We confirm that the singlet stabilizes the electroweak vacuum whilst remaining consistent with zero-temperature phenomenology as well. Thus, this scenario presents an intriguing possibility that aLIGO may detect traces of fundamental physics motivated by vacuum stability at an energy scale that is well above the reach of any other experiment.