The Higgs in the Sky: production of gravitational waves during a first-order phase transition

Abstract

If there was a first order phase transition in the early universe, there should be an associated stochastic background of gravitational waves. The characteristic frequency of the spectrum due to phase transitions which took place at the weak scale is precisely in the window that will be probed by LISA. Taking into account the astrophysical foreground, we determine the type of phase transitions which could be detected either at LISA, LIGO or BBO (Big Bang Observer, the 2nd generation of space interferometers), in terms of the amount of supercooling and the duration of the phase transition that are needed. Those two quantities can be calculated for any given effective scalar potential describing the phase transition. In particular, the new models of electroweak symmetry breaking which have been proposed in the last few years typically have a different Higgs potential from the Standard Model. They could lead to a gravitational wave signature in the milli‐Hertz frequency, which is precisely the peak sensitivity of LISA. Talk given by C. Grojean at Quarks 2006, Repino, Russia and at SUSY’06, Irvine, USA. Based on Ref. [1].