Theoretical Physics Colloquium: Astrophysical probes to new physics beyond the Standard Model

This talk will explore how exciting astrophysical tools, such as gravitational-wave interferometers and the Event Horizon Telescope, can serve as powerful probes of new physics across vastly different mass scales. I will first show that data from the LIGO-Virgo-KAGRA Collaboration can help resolve a long-standing puzzle: whether the GeV gamma-ray excess at the Galactic Center originates from annihilating weakly interacting massive particles or from a population of
millisecond pulsars. Turning to lighter dark matter candidates, I will then demonstrate how the same gravitational-wave detectors enable the direct detection of ultralight bosons, including dark photons, axions, and dilatons. Finally, I will extend this search to axions by shifting to the Event Horizon Telescope, showing how polarization measurements of black-hole images can reveal the presence of axion-like particles through their effects on photon birefringence. Together, these methods illustrate how these newly developed astrophysical frontiers can be repurposed as powerful discovery tools for new physics.

Biography

Yue Zhao is a theoretical particle physicist who focuses on searching for new physics and understanding dark matter.  He joined the Physics & Astronomy Department at the University of Utah in 2018, and he moved to Hong Kong University of Science and Technology as an Associate Professor in 2025.