NPA Zoom Seminar, Devin Walker, Dartmouth College, “Two Stories at the Intersection of Particle Physics and Gravitational Waves”

First Story:
A primordial spectrum of gravitational waves serves as a backlight to the relativistic degrees of freedom of the cosmological fluid. Any change in the particle physics content, due to a change of phase or freeze-out of a species, will leave a characteristic imprint on an otherwise featureless primordial spectrum of gravitational waves and indicate its early-Universe provenance. We show that a gravitational wave detector such as the Laser Interferometer Space Antenna (LISA) would be sensitive to physics near 100 TeV in the presence of a sufficiently strong primordial spectrum. Such a detection could complement searches at newly proposed 100 km circumference accelerators such as the Future Circular Collider at CERN and the Super Proton-Proton Collider in China, thereby providing insight into a host of beyond standard model issues, including the hierarchy problem, dark matter, and baryogenesis.
Second Story:
We describe bosonic mixing in curved spacetime in the presence of external, backgrounds field. We focus on axions and axion-like particles and describe the mixing with electromagnetic and gravitational waves. We describe the modified oscillation probabilities and (time-permitting) some of the observational consequences.
Zoom Info: https://yale.zoom.us/j/93903961284?pwd=empxRWhzdkY5SXpuQ2U2NmR1aWlpZz09