Model Discrimination in Gravitational Wave spectra from Dark Phase Transitions

In anticipation of upcoming gravitational wave experiments, we provide a comprehensive overview of the spectra predicted by phase transitions triggered by states from a dark sector. Such spectra are functions of the quantum numbers and (self-) couplings of the scalar that triggers the dark phase transition. We show how the phase transition can be described in terms of four thermal parameters, which enter into the broken power-law gravitational wave spectrum. We then characterize scenarios in which a measurement of a new source of gravitational waves could allow us to pin down specific models of new physics.