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September 17, 2025 By GeometryAdmin

Klaus Kröncke to speak in geometry seminar 06/10/2025

Klaus Kröncke (Stockholm) will give the geometry seminar on 06/10. The talk will take place at 2pm in the Salle des Profs (9th floor of building NO). Klaus’s title is “On the volume-renormalized mass” and his abstract is below.

We give an overview on results about a new mass-like quantity on asymptotically hyperbolic manifolds, which was recently introduced by Dahl, McCormick and me. The volume-renormalized mass is essentially a linear combination of the ADM mass surface integral and a renormalization of the volume. It is well-defined and diffeomorphism invariant under weaker fall-off conditions than required to ensure that the renormalized volume and the ADM mass surface integral are well-defined separately. We show that our quantity can be deduced from a reduced Hamiltonian perspective and that it is nonincreasing along CMC foliations of asymptotically Milne-like vacuum spacetimes. We prove a positive mass theorem for orientable three-manifolds which don’t contain non-separating spheres. In addition, we demonstrate that a Poincaré–Einstein manifold is dynamically stable under the Ricci flow if and only if it is a local minimizer of the mass. This talk is based on collaborations with Mattias Dahl, Stephen McCormick, Francesca Oronzio, Alan Pinoy and Louis Yudowitz.

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Address

Département de mathématiques
Université libre de Bruxelles CP 218
Boulevard du Triomphe, Bruxelles 1050,
Belgium

Getting here

The department of mathematics is in building NO, on the Campus de la Plaine, of the Université libre de Bruxelles. The geometry group is on the 7th floor. This page has a map of the campus as well as information on how to reach it via public transport. See the STIB website for more information on public transport in Brussels.

Image credits

Polished ammonite fossil, by Kara Stenberg, Creative Commons licence CC BY-NC 2.0.

Model of 3D projection of a 120-cell, by Edmund Harriss.

The root system of the exceptional Lie algebra E8. By Jared Tarbell, Creative Commons Licence CC BY 2.0.

Getting here

The department of mathematics is in building NO, on the Campus de la Plaine, of the Université libre de Bruxelles. The geometry group is on the 7th floor. This map shows NO, as well as the metro station Delta and entrance 2, which is right by the stop for the number 71 and 72 buses. The number 95 also stops a short walk from the department. See the STIB website for more information on public transport in Brussels.

Image credits

Polished ammonite fossil, by Kara Stenberg, Creative Commons licence CC BY-NC 2.0.

Model of 3D projection of a 120-cell, by Edmund Harriss.

The root system of the exceptional Lie algebra E8. By Jared Tarbell, Creative Commons Licence CC BY 2.0.

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