Theory Colloquia at the Physics Department of Torino

Pulsar Timing Array Searches for Gravitational Waves from the Big Bang

In summer 2023, pulsar timing array (PTA) collaborations around the globe announced compelling evidence for a nanohertz gravitational-wave background (GWB)---a breakthrough achievement with important implications for astrophysics and particle physics. The most common interpretation of the new signal is that it originates from a cosmic population of supermassive black-hole binaries. At present, it is, however, also conceivable that it represents a gravitational-wave echo of the Big Bang. In my talk, I will focus on the latter possibility and illustrate how PTA data can be used to probe new particle physics in the early Universe. I will conclude with a brief outlook and explain how future PTA data will help in discriminating between a GWB signal of astrophysical origin and a GWB signal from the Big Bang.

Friday, 21st March 2025, 14:30, Sala Wataghin