8 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…
Infrared physics of QED and gravity from representation theory
Laura Donnay, Yannick Herfray
The infrared structure of QED and gravity is known to be governed by an infinite-dimensional symmetry group which extends the Poincaré group to include, respectively, large …
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…
Carrollian representation from twistor space
Laura Donnay, Laurent Freidel, Yannick Herfray
We construct an explicit realization of the action of the loop algebra on fields at null infinity. This action is directly derived by Penrose transform of the geome…
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…