Features of Cosmological Gravitational Wave Backgrounds

• Fabrizio Rompineve

New Physics in the early Universe may feature sources of gravitational waves (GWs), that can be searched for at interferometers and Pulsar Timing Arrays (PTAs). In this talk, we provide an overview of general properties of such cosmological GWs, that can help in distinguishing them from astrophysical signals. We then focus on cosmic topological defects (specifically, domain walls) as a well-motivated and interesting possible early Universe source of GWs. We present recent progress in the description of their cosmological evolution and their GW signal, as well as on the possibility to produce primordial black holes from their collapse.