Fundamental Physics Seminar Series - Extracting Fundamental Physics through Black-Hole Gravitational-Wave Ringdown Signals
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Abstract
Most gravitational-wave signals detected by the LIGO–Virgo–KAGRA network originate from binary black-hole coalescences. The newly formed black hole is highly distorted immediately after the merger and gradually settles into a stationary state by emitting gravitational waves. These waves exhibit a discrete set of exponentially decaying frequencies known as quasinormal modes. The corresponding phase, called the ringdown, encodes the unique fingerprint of the final black hole. Analyzing quasinormal modes provides a powerful avenue to probe fundamental physics, including stringent tests of general relativity in the strong-field regime. However, obtaining the quasinormal-mode spectrum of generic black holes presents severe mathematical challenges, as it requires solving a complex system of coupled partial differential equations. In this talk, the speaker will introduce METRICS, Metric pErTuRbations wIth speCtral methodS, a spectral formalism that overcomes these difficulties and enables precise computation of quasinormal-mode spectra for general black holes. He will demonstrate how METRICS can be applied to a range of modified gravity theories motivated by high-energy physics, including axi-dilaton, dynamical Chern–Simons, and Einstein–scalar–Gauss–Bonnet theories, to conduct ringdown-only tests of gravity. These analyses yield, among other results, the first observational constraints on axi-dilaton gravity. The speaker will conclude by outlining future applications of METRICS for extracting new insights into fundamental physics through black-hole ringdowns.
About the Speaker
Dr. Adrian Ka-Wai CHUNG is a Herchel Smith Fellow at the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge. An astrophysicist, his research focuses on analysing gravitational waves, ripples in the fabric of space-time that can be produced by the collisions of black holes and neutron stars, to probe fundamental physics, including the limits of Einstein’s general relativity, the nature of dark matter, and the expansion rate of the Universe. Dr. Chung earned his BSc and MPhil in Physics from The Chinese University of Hong Kong. He completed his PhD in Physics at King’s College London in 2022, and subsequently held a postdoctoral position at the University of Illinois Urbana-Champaign from 2022 to 2025 before joining Cambridge.
About the Center for Fundamental Physics
For more information, please refer to https://cfp.hkust.edu.hk/.
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