21. January 2022 - 11:30
Chris Byrnes (University of Sussex)
Abstract: Although black holes can be the remnants of dead stars, some could be primordial. Such primordial black holes are the unique dark matter candidate which is not a new type of particle, and they could also explain some of the unexpected properties of the black hole mergers that LIGO and Virgo have detected. I will summarise the evidence and (fine-tuning) challenges behind this claim. There is a coincidence of scales between the LIGO-Virgo events, the Chandrasekhar limit and the horizon mass during the QCD transition in the early universe, and the wavelength of gravitational waves on which NANOGrav may (potentially) have detected a stochastic gravitational wave background.