Fundamental Physics Seminar Series - Dynamics and Phenomenology of Ultralight Bosons Around Compact Objects

Abstract

Ultralight bosons in the vicinity of compact objects can form gravitationally bound states, some of which undergo exponential growth by extracting rotational energy from black holes or through relaxation from ambient waves. These bound states can attain field amplitudes approaching the Planck scale, giving rise to phenomena analogous to those in early-universe cosmology and to observational signatures far stronger than those expected from local dark matter detection, ranging from electromagnetic features accessible through black hole imaging to gravitational wave imprints of the surrounding environment. In the case of accreting axion clouds, the field can accumulate into approximately spherical configurations with amplitudes near the decay constant, exhibiting either Bosenova collapse or saturation depending on the growth rate and axion mass. The resulting emission flux exhibits discrete spectral features determined by the axion potential, opening the possibility of probing ultraviolet axion models through terrestrial detection of these fluxes.


About the Speaker

Prof. CHEN Yifan is a Tenure-track Fellow at Tsung-Dao Lee Institute, Shanghai Jiao Tong University. He received his bachelor’s degree from the University of Science and Technology of China, his master’s degree from École Polytechnique and Université Paris-Saclay (France), and his PhD from Sorbonne University (France). He subsequently held postdoctoral positions at the Institute of Theoretical Physics, Chinese Academy of Sciences, and at Niels Bohr Institute, the University of Copenhagen (Denmark). His research spans particle physics, gravitational waves and black holes, as well as terrestrial experiments probing fundamental physics.


About the Center for Fundamental Physics

For more information, please refer to https://cfp.hkust.edu.hk/.


For Attendees' Attention

Seating is on a first come, first served basis.