Thursday, August 11th, 2022 at 2 pm. Special Seminar

Speaker: Ricardo Z. Ferreira

Title: Gravitational waves from axion physics

Abstract:

Axions are often accompanied by discrete symmetries that are spontaneously broken in the early universe and lead to the formation of a network of cosmic domain walls (DW).

In this talk, I will show that the stochastic gravitational wave (GW) background produced by the decay of such networks is within reach of current and future detectors. In particular, I will show that DWs annihilating around the QCD phase transition are a good candidate to explain the signals that have been recently observed by different Pulsar Timing Array observatories. On the other hand, the GW signal of DW networks that annihilate at earlier times can lie in the sensitivity band of LIGO and be probed in the next years.

I will finish by discussing a well motivated particle physics example where the DW network can form and generate large GWs - the heavy QCD axion - and show that in this scenario one expects correlated signals at neutron (proton) electric dipole momentum or colliders.