Gravitational waves from electroweak phase transitions

Gravitational waves are generated during first-order phase transitions, either by turbulence or by bubble collisions. If the transition takes place at temperatures of the order of the electroweak scale, the frequency of these gravitational waves is today just within the band of the planned space interferometer LISA. We present a detailed analysis of the production of gravitational waves during an electroweak phase transition in different supersymmetric models where, contrary to the case of the Standard Model, the transition can be first order. We find that the stochastic background of gravitational waves generated by bubble nucleation can reach a maximum value of h(0)(2)Omega(gw) of order (10(-10)-10(-11)), which is within the reach of the planned sensitivity of LISA, while turbulence can even produce signals at the level h(0)(2)Omega(gw) similar to 10(-9). These values of h(0)(2)Omega(gw) are obtained in the regions of the parameter space which can account for the generation of the baryon asymmetry at the electroweak scale. (C) 2002 Elsevier Science B.V. All rights reserved.