Ideas on first evidence of stochastic GW from PTA

The NANOGrav and EPTA collaborations have announced the first evidence of stochastic gravitational wave background (SGWB). There seems to be a slight tension between the data and the astrophysical SGWB prediction from supermassive black hole binary (SMBHB) mergers. Various cosmological sources like short-wavelength scalar perturbations produced during inflation, meta-stable cosmic strings, superstrings, phase transitions, and domain walls decaying to the SM particles are all viable explanations of the observed SGWB signal either stand-alone or together with SMBHB. We explore some of these possibilities in this workshop.

Zoom Link for joining the meeting: https://uw-edu-pl.zoom.us/j/2053143787