# Current seminars

In addition to the Vienna relativity seminars, the calendar above sometimes contains other events of interest to members of the relativity group. The seminars of the Vienna relativity group are listed below.

Location (unless indicated otherwise): Währinger Str. 17

- Room 218 on the 2nd floor for **standard seminars**, and

- Common room, first floor, for **lunch seminars**.

The Mathematical Physics Seminars take place on Tuesdays at 13.45.

The Particle Physics Seminars take place on Tuesdays at 16.15.

- Thursday, March 7th, 14:00, Seminarraum A

Piotr Chrusciel (Vienna):*Positivity of hyperbolic mass*

Abstract: I will present the proof of positivity of hyperbolic mass in all dimensions for asymptotically hyperbolic manifolds with spherical conformal infinity. Based on joint work with Erwann Delay arXiv:1901.05263

- Thursday, March 14th, 14:00, Seminarraum A

Piotr Bizon (Krakov):*A nonrelativistic limit of AdS perturbations*

Abstract: I will discuss dynamics of small amplitude solutions of the Schroedinger-Newton system with an external harmonic potential. This system arises in a nonrelativistic limit from the Einstein-Klein-Gordon equations with a negative cosmological constant. The main goal is to understand the resonant transfer of energy to small spatial scales.

- Friday, March 15th, 13:00, Lunch Seminar

Tim Paetz (Vienna):*On the choice of a conformal Gauss gauge near the cylinder representing spatial infinity*

Abstract: A convenient approach to analyze spatial infinity is to use a cylinder representation and impose a gauge based on a congruence of conformal geodesics. This so-called conformal Gauss gauge comes along with the freedom to specify initial data for the conformal geodesics. Such a gauge has been constructed from an ordinary Cauchy surface and from past null infinity, respectively. In this talk we compare these gauges near the critical set, where the cylinder "touches" past null infinity, as it turns out that they are related in a somewhat unexpected intricate way.

- Monday, March 18th, 13:00, Lunch Seminar Seminarraum A

Gernot Heißel (Vienna):*Kantowski-Sachs cosmology with Vlasov matter*

Abstract: We analyse the Kantowski-Sachs cosmologies with Vlasov matter of massive and massless particles using dynamical systems analysis. We show that generic solutions are past and future asymptotic to the non-flat locally rotationally symmetric Kasner vacuum solution. Furthermore, we establish that solutions with massive Vlasov matter behave like solutions with massless Vlasov matter towards the singularities.

- Thursday, March 21th (as part of the joint relativity-geometric analysis seminar), 14:00, ESI

Marc Henneaux (Bruxelles):*Asymptotic symmetries of electromagnetism and gravity: a Hamiltonian study*

Abstract: The asymptotic symmetries of gravity and electromagnetism are remarkably rich. The talk will explain the asymptotic structure of gravity and electromagnetism in the asymptotically flat case by making central use of the Hamiltonian formalism. In particular, how the relevant infinite-dimensional asymptotic symmetry groups emerge at spatial infinity, and the extension to higher spacetime dimensions, will be discussed.

- Thursday, March 28th (as part of the joint relativity-geometric analysis seminar), 13:30, Seminarraum A

Simon Raulot (Rouen):*Yamabe invariants and Cheeger constant on Poincaré-Einstein manifolds*

Abstract: In the first part of this talk, we present an elementary proof of the rigidity of the hyperbolic space as the unique Poincaré-Einstein manifold whose boundary at infinity is the conformal round sphere. The proof relies on an inequality which relates the Yamabe invariant of the boundary with the one of a compactification of the bulk manifold. In a second part, we relate the Cheeger constant of such manifolds with the conformal type of the boundary at infinity . More precisely, we prove that this constant is exactly the dimension of the interior of the Poincaré-Einstein manifold if and only if the Yamabe invariant of the boundary is non negative. Several applications are then discussed.

- Thursday, April 4th, 14:00, Seminarraum A

Mikolaj Korzynski (Warsaw):*Probing the spacetime curvature using geometric optics*

Abstract: In general relativity light propagation is affected by gravity, leading to the well-known effects of light bending, Shapiro delays and gravitational redshift. On top of that the results of observation of light by an observer are also affected by the special relativistic phenomena like the aberration or time dilation. All these effects influence the measurements of shape, parallax, redshift and position drift (proper motion) of distant objects. We show that all results of those measurements can be understood as functions of the curvature along the line of sight. This opens up the possibility to probe the spacetime curvature directly using only optical observations.

- Thursday, April 11th, 14:00, Seminarraum A

Thomas Schuecker (Marseille):*(tba)*

Abstract:

- Thursday, May 9th, 14:00, Seminarraum A

Leo Bigorgne (Orsay):*(tba)*

Abstract:

- Thursday, May 16th (as part of the joint relativity-mathematical seminar), 14:00, Seminarraum A

Stefan Fredenhagen (Vienna):*(tba)*

Abstract:

- Thursday, May 23th, 14:00, Seminarraum A

Daniel Grumiller (TU Wien):*(tba)*

Abstract:

- Thursday, May 30th (as part of the joint theory seminar), 14:00, Seminarraum A

Robert Brandenberger (McGill):*(tba)*

Abstract: