Gravitational waves from vacuum first-order phase transitions: From the envelope to the lattice

Abstract

We conduct large scale numerical simulations of gravitational wave production at a first-order vacuum phase transition. We find a power law for the gravitational wave power spectrum at high wavenumber which falls off as k −1.5 rather than the k −1 produced by the envelope approximation. The peak of the power spectrum is shifted to slightly lower wave numbers from that of the envelope approximation. The envelope approximation reproduces our results for the peak power less well, agreeing only to within an order of magnitude. After the bubbles finish colliding the scalar field oscillates around the true vacuum. An additional feature is produced in the UV of the gravitational wave power spectrum, and this continues to grow linearly until the end of our simulation. The additional feature peaks at a length scale close to the bubble wall thickness and is shown to have a negligible contribution to the energy in gravitational waves, providing the scalar field mass is much smaller than the Planck mass.

Detecting gravitational waves from cosmological phase transitions with LISA: an update

“…For the observed value of the Higgs mass, x > 0.11 in the SM and the methods described above predict a smooth cross-over. However, in certain regions of parameter space, scenarios beyond the SM can be matched on to the 3D effective theory described by (46). One can thereby extract information about the phase structure in BSM theories from existing SM lattice studies.…”

“…In order for (46) to be an accurate description of the long distance physics, the new degrees of freedom introduced in the model should be heavy at the PT (so that they can be integrated out), new contributions to higher-dimensionalal operators induced by integrating out the new fields should be small enough to neglect, and couplings should be small enough so that the perturbative matching procedure of DR accurately described the underlying theory. This matching onto the theory described by (46) has been performed for the singlet, doublet and triplet models (discussed further below) and existing lattice results used to study the phase structure in certain regions of parameter space. In each case, these studies [88,89,[115][116][117] have found phenomenologically viable regions of the parameter space predicting a first-order PT.…”

“…The 3D theory described by (46) can only go so far in describing BSM scenarios. As emphasized in e.g.…”

“…To date very few 3D theories besides (46) have been studied nonperturbatively. Examples include the 2HDM, which introduces an additional SU (2) Higgs doublet field to (46), and the MSSM, for which the 3D theory includes two SU (2) Higgs doublets and one SU (3) triplet, corresponding to the right-handed stop field. In the 2HDM, [67] confirmed that there are phenomenologically viable parameter space points predicting a relatively strong first-order PT.…”

Quantum transport and the phase space structure of the Wightman functions

“…1 This is encouraging for the application of semiclassical methods in the related problem of electroweak phase baryogenesis with very strong electroweak phase transitions. These typically create sharp transition walls and are often encountered in the context of models producing large, observable gravitational wave signals [13][14][15][16][17][18].…”