Probing Dark Sectors with Gravitational Waves*

One of the greatest unsolved mysteries in particle physics is the nature of dark matter. So far no indisputable direct dark matter detection has been made. It might be that the dark matter particle is part of a dark sector which is secluded or extremely weakly coupled to the visible sector, in which case conventional experiments might never detect it. As I will demonstrate, gravitational waves arising from first order phase transitions in the early Universe can be used to look for signatures of such models. Focusing on particular extensions of the Standard Model with dark U(1) and dark SU(2) gauge groups, I will show how such signatures can be searched for in upcoming gravitational wave experiments, such as LISA, SKA, PPTA, EPTA, IPTA, as well as discuss how the recent NANOGrav gravitational wave signal can be accommodated in this scenario. I will also investigate connections of those models to the existing particle physics anomalies, e.g., the neutron lifetime anomaly.