Gravitational waves from first order phase transitions in the early universe

We present the results of large-scale 3D simulations of first order phase transitions in the early universe. The fluid is included for the first time, allowing us to tune the wall velocity. The transition proceeds by the nucleation, growth, and collision of bubbles of the new phase in the coupled scalar field-fluid system. The resulting gravitational wave and fluid power spectra are calculated for a variety of detonations and deflagrations. In these preliminary results, we already see departures from the widely used "envelope approximation". For sufficiently large latent heat, the techniques are applicable to first-order phase transitions occurring in QCD-like extensions of the weak sector.