April 20th
when: Tuesday 20/4/2021, 12:30 (seminar starts at 12:45)
where: Zoom meeting!
speaker: Edward Hardy
Title: Observing Invisible Axions with Gravitational Waves
abstract: If the Peccei-Quinn symmetry associated to an axion has ever been restored after inflation, axion strings inevitably produce a contribution to the stochastic gravitational wave background. Combining effective field theory analysis with numerical simulations, I will show that the resulting gravitational wave spectrum has logarithmic deviations from a scale invariant foirm with an amplitude that is significantly enhanced at low frequencies. I will discuss the implications for upcoming experiments and the complementary cosmological constraints.