Speaker
Description
The nanohertz gravitational-wave (GW) signal observed by pulsar timing arrays may originate from a cosmological first-order phase transition (FOPT) at temperatures of order 100 MeV. This coincidence raises a fundamental question: why this scale? We show that such a PT naturally arises in scenarios where the baryon asymmetry is generated from a dark asymmetry via resonant neutron-dark matter (DM) oscillations.
We demonstrate that the same PT can produce a GW signal compatible with NANOGrav observations while satisfying all current experimental and cosmological constraints. The framework predicts DM self-interactions close to observational bounds and a reduced maximum mass for neutron stars. It also offers complementary probes through missing-energy searches at the LHC and neutron decay experiments.
Consistency with big-bang nucleosynthesis is ensured by introducing O (10-100) MeV scale heavy neutral leptons, which simultaneously account for neutrino masses and provide additional experimental signatures.