12:00–1:00 pm Zoom Room (online)
Hongwan Liu, Princeton University and New York University, "Dark Photon Oscillations in our Inhomogeneous Universe"
The dark photon is a well-motivated extension of the Standard Model which can mix with the regular photon. This mixing is enhanced whenever the dark photon mass matches the primordial plasma frequency, leading to resonant conversions between photons and dark photons at specific redshifts. These conversions can produce observable cosmological signatures, including distortions to the cosmic microwave background blackbody spectrum. Until recently, constraints on the dark photon based on these effects have been derived assuming a homogeneous universe. In this talk, I will review the physics of photon/dark-photon mixing, and introduce a new analytic formalism that can account for the inhomogeneous distribution of matter in our universe. Using this formalism, we obtain new limits on the dark photon mixing parameter, significantly correcting and extending earlier results.