Gravitational Waves as a Window on Conformal Neutrino-Mass Models

Covering a broad frequency range — from millihertz space interferometers up to the kilohertz band of ground-based detectors — this talk discusses how primordial gravitational waves can probe High-Energy Physics beyond the Standard Model.

Focusing on supercooled first-order phase transitions in (classically) conformal U(1)′ extensions that account for neutrino masses via the type-I seesaw (Majoron-like realizations), I show how the predicted stochastic GW background becomes tightly linked to the symmetry-breaking scale, couplings, and the heavy-neutrino sector, with present LVK data already constraining parts of parameter space and future LISA/ET observations offering decisive tests.

Building on this, I highlight how sufficiently strong and long-lasting transitions can simultaneously source primordial black holes and primordial magnetic fields, enabling multi-messenger correlations with microlensing and gamma-ray probes.