Gravitational waves from cosmological phase transitions

Understand

I discuss the generation of a stochastic background of gravitational waves during a first order phase transition.

• I present simple general arguments which explain the main features of the gravitational wave spectrum like the $k^3$ power law growth on large scales and a estimate for the peak amplitude.
• In the second part I concentrate on the electroweak phase transition and argue that the nucleosynthesis bound on its gravitational wave background seriously limits seed magnetic fields which may have been generated during this transition.