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SUMMARY:David Pereniguez Rodriguez "Gravitational Duality at the Lightring
 \, QNM isospectrality\, and Ringdown Nonlinearities from Penrose Limits"
DTSTART:20260304T113000Z
DTEND:20260304T133000Z
DTSTAMP:20260502T084300Z
UID:indico-event-51245@agenda.infn.it
CONTACT:dpereni1@jh.edu
DESCRIPTION:At high frequencies\, the physics near a black hole’s lightr
 ing can be captured by Penrose-limit plane waves adapted to the photon sph
 ere. In this talk\, I will solve exactly the equations for gravitational p
 erturbations in this limit using Penrose’s 2-spinor formalism\, and I wi
 ll show that the resulting solutions correspond to quasinormal modes (QNMs
 ) in the eikonal regime. I will then prove that gravitational electric–
 magnetic duality holds on-shell for perturbations at the lightring. This s
 ymmetry has long been understood to hold on-shell only for perturbations a
 bout flat spacetime. The lightring therefore provides a distinct setting i
 n which it reemerges. In addition\, QNM isospectrality follows as an immed
 iate consequence. I will next extend the analysis to nonlinear gravitatio
 nal fluctuations\, where the duality is broken\, and compute the excitatio
 n of quadratic QNMs\, which are particularly relevant given recent prospec
 ts for their detection. I will conclude by discussing further directions i
 n which Penrose limits can be used to sharpen our understanding of lightri
 ng physics.\n\nhttps://agenda.infn.it/event/51245/
LOCATION:Sala Lauree (Marconi Building) (La Sapienza)
URL:https://agenda.infn.it/event/51245/
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