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SUMMARY:Black-hole METRICS\, ringdown and fundamental physics - Adrian Ka-
 Wai Chung\, DAMTP
DTSTART:20260123T130000Z
DTEND:20260123T140000Z
UID:TALK243325@talks.cam.ac.uk
CONTACT:Lorenzo Gavassino
DESCRIPTION: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 gra
 dually settles into a stationary state by emitting gravitational waves. Th
 ese waves exhibit a discrete set of exponentially decaying frequencies kno
 wn as quasinormal modes. The corresponding phase\, called the ringdown\, e
 ncodes the unique fingerprint of the final black hole. Analyzing quasinorm
 al modes provides a powerful avenue to probe fundamental physics\, includi
 ng stringent tests of general relativity in the strong-field regime. Howev
 er\, obtaining the quasinormal-mode spectrum of generic black holes presen
 ts severe mathematical challenges\, as it requires solving a complex syste
 m of coupled partial differential equations. In this talk\, I will introd
 uce METRICS\, Metric pErTuRbations wIth speCtral methodS\, a spectral form
 alism that overcomes these difficulties and enables precise computation of
  quasinormal-mode spectra for general black holes. I will demonstrate how 
 METRICS can be applied to a range of modified gravity theories motivated b
 y high-energy physics\, including axi-dilaton\, dynamical Chern-Simons\, a
 nd Einstein-scalar-Gauss-Bonnet theories\, to conduct ringdown-only tests 
 of gravity. These analyses yield\, among other results\, the first observa
 tional constraints on axi-dilaton gravity. If time permits\, I will mentio
 n the results of the recent first accurate construction of nearly extremal
  black holes in modified gravity theories. I will conclude by outlining f
 uture applications of METRICS for extracting new insights into fundamental
  physics through black-hole ringdowns.
LOCATION:Potter Room / Zoom :  https://cam-ac-uk.zoom.us/j/85131795570
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