Gravitational waves from the electroweak phase transition
  We study the generation of gravitational waves in the electroweak phase
transition. We consider a few extensions of the Standard Model, namely, the
addition of scalar singlets, the minimal supersymmetric extension, and the
addition of TeV fermions. For each model we consider the complete dynamics of
the phase transition. In particular, we estimate the friction force acting on
bubble walls, and we take into account the fact that they can propagate either
as detonations or as deflagrations preceded by shock fronts, or they can run
away. We compute the peak frequency and peak intensity of the gravitational
radiation generated by bubble collisions and turbulence. We discuss the
detectability by proposed spaceborne detectors. For the models we considered,
runaway walls require significant fine tuning of the parameters, and the
gravitational wave signal from bubble collisions is generally much weaker than
that from turbulence. Although the predicted signal is in most cases rather low
for the sensitivity of LISA, models with strongly coupled extra scalars reach
this sensitivity for frequencies $f\sim 10^{-4}\,\mathrm{Hz}$, and give
intensities as high as $h^2\Omega_{\mathrm{GW}}\sim 10^{-8}$.
