Speaker
Description
I will discuss some of the directions in which a Gravitational Wave (GW) background can shed light on fundamental physics and cosmology.
Model-independent information can be extracted from the low-frequency tail of the spectrum, which is dictated by causality for any primordial GW source active for a finite time (as a phase transition). The causality tail allows to probe the Hubble rate and the equation-of-state of the Universe around the GW production time, and the presence of free-streaming particles at primordial epochs. I will comment on the discrimination of this signal from astrophysical backgrounds, and on the implication for Pulsar Timing Arrays, where the QCD crossover of the SM unavoidably affects a primordial GW signal.
I will then discuss some interesting connections between the detection of a primordial GW background and the preferred parameter space for dark matter searches, or its implications for the gauge-group structure of SM extensions, with a particular focus on flavour models.