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03/06/2026 10:15
I will present a unified treatment for the boundary geometry of asymptotically flat spacetimes and black hole horizons. This geometric duality implies an exact inversion isometry for extremal, non-rotating horizons, which will be used to relate and derive new infinite towers of conserved quantities.
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03/06/2026 11:00
The Kerr metrics model rotating vacuum black holes, and are expected to play a central role in the long-time description of generic solutions to the Einstein vacuum equation. They present the disturbing feature that determinism breaks down inside the black hole, beyond the Cauchy horizon. Penrose's Strong Cosmic Censorship conjecture states that this behavior is however unstable and vanishes...
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03/06/2026 14:00
Tidal Love numbers quantify the deformability of compact objects under external tidal fields. They are key quantities in gravitational‑wave astronomy for accurately modeling waveforms during the final stage of an inspiral and carry information about the microphysics of the object. I will present a framework for computing tidal Love numbers beyond linear order by matching relativistic...
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03/06/2026 14:45
Black holes gradually settle into their static configuration by emitting gravitational waves, whose amplitude diminish over time according to a power-law decay at fixed spatial locations. We show that the nonlinear tails in the presence of a quadratic source, which have been recently found to potentially dominate over the linear ones, can be simply derived from the AdS_2 × S^2 spacetime...
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03/06/2026 16:00
Modelled on the Anti-de Sitter space, asymptotically Anti-de Sitter spaces can be defined as Lorentzian manifolds that possess a timelike conformal boundary. Due to their lack of global hyperbolicity, finding asymptotically Anti-de Sitter solutions to the Einstein equations (necessarily with a negative cosmological constant) through the Cauchy problem requires tackling the latter as an initial...
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03/06/2026 16:45
The space of solutions to the free equations of motion for massless fields of arbitrary integer spin in Minkowski spacetime is recovered as a smooth limit of the anti-de Sitter solution space for any even spacetime dimension. The infinite set of boundary data near null infinity that characterise solutions in Minkowski spacetime is obtained from an expansion of the anti-de Sitter source and vev...
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03/06/2026 17:10
In this talk, I plan to discuss dynamical scalar Love numbers for two types of static wormhole metrics. I will also discuss how these numbers may make it possible to distinguish not only black holes from wormholes, but also different types of wormholes that appear topologically similar, at least at first glance.
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03/06/2026 17:35
I will present a work in collaboration with P.G. LeFloch and Yue Ma on the nonlinear stability of Minkowski spacetime. We consider the massive Einstein-Dirac system and investigate the global evolution problem when the initial data are sufficiently close to those describing a spacelike, asymptotically Euclidean slice in Minkowski spacetime. We establish the existence of a globally hyperbolic...
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04/06/2026 09:00
The Kerr metric enjoys a special symmetry known as circularity, which is normally assumed when constructing rotating black hole solutions in alternative theories of gravity and when building Kerr-mimicker models. In this talk I will examine how justified this assumption is and what happens when it breaks. Working within a geometrically natural gauge, the circularity conditions are solved...
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04/06/2026 10:15
The launch of relativistic jets of plasma on astrophysical to cosmological scales is observed in a variety of astrophysical sources, from active galactic nuclei to X-ray binaries. While these jets can be reproduced by general relativistic magneto-hydrodynamics (GRMHD) and particle-in- cells (GRPIC) simulations of the dynamical Kerr magnetosphere, the development of analytic models to describe...
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04/06/2026 11:00
The seminal result by H. Friedrich on the semiglobal stability of the Minkowski spacetime shows that hyperboloidal initial data for the Einstein field equations which is suitably close to data for the Minkowski spacetime and conformally smooth gives rise to a future development which is future geodesically complete and has the same global structure as the comparable region in the Minkowski...
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04/06/2026 14:00
Initially defined in the context of General Relativity, the ADM mass is an important invariant of Riemannian asymptotically flat manifolds. Some 25 years ago, L. Habermann used it to answer a question in pure Riemannian geometry : finding a canonical metric in each conformal class of Riemannian metrics with positive scalar curvature on a compact manifold of dimension 3, 4, or 5. Despite the...
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04/06/2026 14:45
I will present recent results on positive energy theorems for the Einstein–Maxwell equations in the setting of asymptotically flat spin initial data. A spinorial approach leads to positivity results for the total energy–momentum.
We then focus on questions in the Riemannian setting. This naturally leads to the notion of charged parallel spinors, whose existence is closely tied to the...
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04/06/2026 16:00
Quantum gravity remains fragmented across scales and frameworks: in the UV, a number of alternative theories aim to describe the fundamental aspects of gravity; in the IR, EFT considerations and observations can constrain beyond GR physics in a theory-agnostic fashion.
Rather than treating these domains as separate, I will argue for a unifying approach: by extending the logic of the...
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04/06/2026 16:45
According to Strominger, Weinberg's soft graviton theorem is related to the fact that the BMS group is a symmetry of the S matrix. For this to even make sense, the BMS group must be promoted from two BMS groups acting on asymptotic states to a global BMS group. In this, spatial infinity plays a pivotal role as the link between the two. In this talk, we will introduce an extended boundary,...
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04/06/2026 17:10
I plan to discuss applications of the Gauge PDE formalism to the study of gauge field theories with asymptotic boundaries. The main ingredient is a notion of compactification for gauge field theories inspired by graded geometry, leading to a natural generalization of Penrose's idea of conformal compactification of gravity. As an application, the resulting framework gives rise to natural action...
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04/06/2026 17:35
Abstract: The large-distance behaviour of a sandwich gravitational wave by a continuous but not necessarily smooth profile provides us with an approximate analytic description of particle motion in a gravitational wave, as spelled out for the Pöschl-Teller profile. Our approximate models are consistent with the Carroll symmetry.
Authors: Q-L Zhao (Hangzhou), P.-M. Zhang (Zhuhai), M....
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05/06/2026 09:00
In this talk we describe a method for deriving exact metric solutions from a cubic worldline action in every dimensions from an amplitude computation. With this formalism one can derive the geodesic motions of a test particle in such background. The same formalism is suitable for the self-force expansion in a post Minkowskian formalism.
This is based on work with Stavros Mougiakakos and...
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05/06/2026 10:15
During the talk, I will present the results obtained in collaboration with Romain Gicquaud concerning the classical construction of initial data using the conformal method, which was originally proposed by Holst, Nagy and Tsogtgerel and later refined by Maxwell. This method transforms the usual constraint equation for initial data in general relativity into a set of two coupled nonlinear...
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05/06/2026 11:00
In this talk, I will present our recent work on post-Minkowskian EFT for scalar-tensor theories and boson stars. We first derive the analytical expressions of the scattering angle using PM-EFT techniques for both the cases, and in particular provide the first analytical treatment of boson stars as a two-body problem. We then derive the effective-one-body description of these systems. We then...
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05/06/2026 14:00
I will investigate the asymptotic symmetries of four-dimensional asymptotically flat spacetimes at spatial infinity using covariant phase space methods. I will show that novel symmetries can be realized—beyond those identified at null infinity—namely logarithmic translations and log supertranslations. The associated charges are finite and conserved, and we show that their algebra admits...
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05/06/2026 14:45
Tidal Love numbers quantify the finite-size properties of Black Holes and Neutron Stars, such as absorption, dissipation and their response to external fields. Perhaps surprisingly, even in classical general relativity, they undergo renormalization group running due to nonlinearities. In this talk I will explain some exact results about their running, which can be extracted using scattering...
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