7 papers
Taming the Aretakis instability: extremal black holes with multi-degenerate horizons
Shreyansh Agrawal, Panagiotis Charalambous, Laura Donnay +2
Stationary black hole geometries with non-degenerate Cauchy horizons are classically unstable due to mass inflation. At extremality, mass inflation is absent, but a different dynam…
Null infinity as an inverted extremal horizon: Matching an infinite set of conserved quantities for gravitational perturbations
Shreyansh Agrawal, Panagiotis Charalambous, Laura Donnay
Every spacetime that is asymptotically flat near null infinity can be conformally mapped via a spatial inversion onto the geometry around an extremal, non-rotating and non-expandin…
Generalized Couch--Torrence inversions
Panagiotis Charalambous, Laura Donnay, Alexandru Lupsasca
The Laplace equation on Euclidean flat space admits a discrete radial inversion symmetry. In 1983, Couch and Torrence (CT) found -- surprisingly -- that the massless wave equation…
Celestial algebra in Einstein-Yang-Mills theory
Shreyansh Agrawal, Panagiotis Charalambous, Laura Donnay
From a study of the subleading structure of the asymptotic equations of motion in Einstein-Yang-Mills theory, we construct charges that are conserved up to quadratic order in non-r…
Love numbers of black p-branes: fine tuning, Love symmetries, and their geometrization
Panagiotis Charalambous, Sergei Dubovsky, Mikhail M. Ivanov
We compute scalar static response coefficients (Love numbers) of non-dilatonic black -brane solutions in higher dimensional supergravity. This calculation revels a fine-tuning b…
Magic zeroes in the black hole response problem and a Love symmetry resolution
Panagiotis Charalambous
In this thesis, we present the emergence of an ("Love") symmetry in the suitably defined near-zone region, relevant for studying the black hole response problem. This sym…