Speaker
Description
Scalar induced gravitational waves (SIGW) are a powerful probe of dynamics in the Standard Model and BSM models in the early Universe. In particular, the equation of state and sound speed have a non-trivial time dependence during phase transitions, which will impact the spectrum of induced GWs. In this talk, I will present a detailed calculation of SIGW in a general time-dependent thermal bath. We derive general initial conditions for metric perturbations in the superhorizon limit, and explain special features of the GW spectrum associated with phase transitions. I will show that the QCD crossover can leave observable features in the Pulsar Timing Array window, while BSM phase transitions, such as in composite Higgs models, can be probed by LISA, Taiji and TianQin.
