Domain Walls in the early Universe and their gravitational signatures

by Fabrizio Rompineve

Wednesday 4 Jun 2025, 14:30 → 15:30 Europe/Rome

Particle physics scenarios with discrete symmetries can be probed by searching for their cosmological relics. When the symmetry is spontaneously broken in the early Universe, a network of topological defects (domain walls) is formed, that generically ends up making a large fraction of the energy budget of the Universe. While these defects are required to decay away in light species before dominating, they are efficient sources of a stochastic gravitational wave (GW) background, that can be detected at interferometers and Pulsar Timing Arrays. In this talk, after introducing the general properties of domain wall networks and of their particle physics implementations, we present results from modern simulations of domain walls in the expanding Universe, in particular focusing on the spectrum of radiated GWs. We then discuss the presence of dark matter relics from DWs, in particular primordial black holes, and their possible connection to the QCD axion scenario.