Jonas Matuszak (KIT)

Probing Dark Matter with Pulsar Timing Arrays

The latest data release of pulsar timing array (PTA) observatories has provided decisive evidence for a stochastic gravitational wave (GW) signal at nano-Hertz frequencies. Future analysis are expected to confirm this signal with discovery-level significance. While the standard astrophysical explanation of the signal is the merging of black hole binaries, it can be improved by introducing an additional cosmological source of a stochastic GW signal. An intriguing possibility is that a dark sector contributes to the signal through a cosmological first order phase transition. I will present a model which gives rise to a stochastic GW signal through the spontaneous breaking of a classical conformal symmetry and additionally sources the mass of a fermionic sub-GeV dark matter candidate. The dark matter relic abundance is achieved via the thermal freeze-out mechanism. I will discuss the phenomenological implications, such as testability though collider experiments and cosmological observations. Finally, I will present TransitionListener, a computational tool developed in this analysis to compute the GW signal of dark sector phase transitions, which will be publicly released in the near future.