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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:1
UID:UW-Physics-Event-8012
DTSTART:20221122T200000Z
DTEND:20221122T210000Z
DTSTAMP:20260414T152658Z
LAST-MODIFIED:20221117T230409Z
LOCATION:https://berkeley.zoom.us/j/91230714547
SUMMARY:Constraining modifications of black hole perturbation potentia
 ls near the light ring with quasinormal modes\, Network in Neutrinos\,
  Nuclear Astrophysics\, and Symmetries (N3AS) Seminar\, Nicola Franchi
 ni \, APC\, Paris/CPB\, Berkeley
DESCRIPTION:In modified theories of gravity\, the potentials appearing
  in the Schrodinger-like equations that describe perturbations of nonr
 otating black holes are also modified. Can these modifications be cons
 trained with high-precision gravitational-wave measurements of the bla
 ck hole's quasinormal mode frequencies? By assuming the modifications 
 to be proportional to a small perturbation parameter\, and parametrize
 d by a Taylor expansion in M/r\, we compute the quasinormal modes of t
 he modified potential up to quadratic order in the perturbative parame
 ter. Either through a principal component analysis or via Markov-chain
 -Monte-Carlo methods we try to recover the Taylor coefficients in the 
 M/r. In both cases\, even if the overall reconstruction is good\, we f
 ind that the bounds on the individual parameters are not robust. Becau
 se quasinormal mode frequencies are related to the behaviour of the pe
 rturbation potential near the light ring\, we propose a different stra
 tegy. We map the Taylor expansion to the value of the potential and it
 s derivatives at the peak by using Wentzel–Kramers–Brillouin theor
 y\, and we demonstrate that the value of the potential and its second 
 derivative at the light ring can be robustly constrained. These constr
 aints allow for a more direct comparison between tests based on black 
 hole spectroscopy and observations of black hole ``shadows'' by the Ev
 ent Horizon Telescope and future instruments.
URL:https://www.physics.wisc.edu/events/?id=8012
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