Gravitational waves from a supercooled electroweak phase transition and their detection with pulsar timing arrays

Abstract

We investigate the properties of a stochastic gravitational wave background produced by a first-order electroweak phase transition in the regime of extreme supercooling. We study a scenario whereby the percolation temperature that signifies the completion of the transition, T p , is as low as a few MeV (nucleosynthesis temperature), while most of the true vacuum bubbles are formed much earlier at the nucleation temperature, T n ∼ 50 GeV. This implies that the gravitational wave spectrum is mainly produced by the collisions of large bubbles and characterised by a large amplitude and a peak frequency as low as f ∼ 10 −9 −10 −7 Hz. We show that such a scenario can occur in (but not limited to) a model based on a non-linear realisation of the electroweak gauge group, so that the Higgs vacuum configuration is altered by a cubic coupling. In order to carefully quantify the evolution of the phase transition of this model over such a wide temperature range we go beyond the usual fast transition approximation, taking into account the expansion of the Universe as well as the behaviour of the nucleation probability at low temperatures. Our computation shows that there exists a range of parameters for which the gravitational wave spectrum lies at the edge between the exclusion limits of current pulsar timing array experiments and the detection band of the future Square Kilometre Array observatory.

Dark, cold, and noisy: constraining secluded hidden sectors with gravitational waves

“…Strictly speaking, we should here distinguish between the temperature at which gravitational waves are emitted (usually referred to as T * ) and T nuc . The two temperatures may be different if the latent heat released during the phase transitions heats the plasma considerably compared to its initial temperature, as could be the case for instance for a phase transition happening during a vacuum-dominated epoch[5,[41][42][43][44][45][46][47][48][49][50][51][52]. However, in the following we will only consider phase transitions occurring during radiation domination, and we will therefore set T * = T nuc in the rest of this paper.…”

Gravitational wave and collider signals in complex two-Higgs doublet model with dynamical CP -violation at finite temperature

“…It is worthy noticing that the above formulae of the GW spectrum for the three sources, which is given by numerical simulation, are based on a rapid phase transition process and α < 1. Since a supercooling FOPT may induce a longer and stronger transitions [56,57], it is not clear whether these formulae are applicable to this situation.…”

Neutrino mass without lepton number violation, dark matter; and a strongly first-order phase transition

“…The deviation ∆λ hhh (≡ λ hhh − λ The strongly first-order phase transition in the early Universe can also be tested by detecting the characteristic spectrum of gravitational waves (GWs) [43][44][45][46][47][48][49] at future space based GW interferometers such as LISA [50], DECIGO [51] and BBO [52]. In particular, it has been decided that LISA will start in relatively near future [50].…”