5 February 2026
3:30pm CET
DAVID MAXWELL
(University of Alaska, Fairbanks, United States)
Title: Einstein-Fluid Initial Data
Abstract: Fluids are a standard matter source for gravitation, going back to the early days of general relativity. Nevertheless, constructing initial data for this family of matter models is surprisingly nuanced. In this talk we describe a novel approach to building Einstein-fluid initial data based on a recently established phase-space technique for constructing non-vacuum initial data sets. Compared to prior approaches to working with fluids, the input parameters allow for more direct specification of physical quantities, such as the number of particles in any given region. We focus on perfect fluids but also touch on extensions of these ideas
to viscous models.
5 March 2026
3:30pm CET
GILBERT WEINSTEIN
(Ariel University, Israel)
Title: The mass angular momentum inequality
Abstract: In this talk,I will discuss our recent result. Either there is a counterexample to black hole uniqueness, or the following statement holds. Axisymmetric, complete, simply connected, maximal initial data sets for the Einstein equations of nonnegative energy density with ends that are either asymptotically flat or asymptotically cylindrical, admit an ADM mass lower bound given by the square root of total angular momentum. Moreover, equality is achieved only for a constant time slice of an extreme Kerr spacetime. The proof is based on a novel flow of singular harmonic maps with hyperbolic plane target, under which the renormalized harmonic energy is monotonically nonincreasing. Relevant properties of the flow are achieved through a refined asymptotic analysis of solutions to the linearized harmonic map equations.
This is joint work with Qing Han, Marcus Khuri, and Jingang Xiong.
2 April 2026
3:30pm CEST
MARIEM MAGDY
(Perimeter Institute & Fields Institute, Canada)
Title: tba
Abstract: tba