Gravitational waves from deflagration bubbles in first-order phase transitions

Abstract

The walls of bubbles in a first-order phase transition can propagate either as detonations, with a velocity larger than the speed of sound, or deflagrations, which are subsonic. We calculate the gravitational radiation that is produced by turbulence during a phase transition which develops via deflagration bubbles. We take into account the fact that a deflagration wall is preceded by a shock front which distributes the latent heat throughout space and influences other bubbles. We show that turbulence can induce peak values of ${\ensuremath{\Omega}}_{\mathrm{GW}}$ as high as $\ensuremath{\sim}{10}^{\ensuremath{-}9}$. We discuss the possibility of detecting at LISA (Laser Interferometer Space Antennae) gravitational waves produced in the electroweak phase transition with wall velocities ${v}_{w}\ensuremath{\lesssim}{10}^{\ensuremath{-}1}$, which favor electroweak baryogenesis.