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.

Unless explicitly stated otherwise, the regular (not-lunch) relativity seminars
take place in Room 218
**2nd floor, Währingerstrasse 17.**

The Mathematical Physics Seminars take place on Tuesdays at 14.15.

The Particle Physics Seminars take place on Tuesdays at 16.15.

- Thursday,
**March 23**, 14:00, Andrzej Rostworowski (Cracow):*Higher order perturbations of Anti-de Sitter space and time-periodic solutions of vacuum Einstein equations*

Abstract:
Motivated by the problem of stability of Anti-de Sitter (AdS) spacetime, I will discuss nonlinear gravitational perturbations of maximally symmetric solutions of vacuum Einstein equations in general and the case of AdS in particular. I will present the evidence that, similarly to the self-gravitating scalar field at spherical symmetry, the negative cosmological constant allows for the existence of globally regular, asymptotically AdS, time-periodic solutions of vacuum Einstein equations that bifurcate from linear eigenfrequencies of AdS. Interestingly, preliminary results indicate that the number of time-periodic solutions bifurcating from a given eigenfrequency equals the multiplicity of
this eigenfrequency. The talk will be based on the recent preprint
https://arxiv.org/abs/1701.07804

- Wednesday,
**March 29**, lunch seminar, 13:00, Elik Olami (Jerusalem):*Continuum dynamics on manifolds: Applications to Elasticity of Residually-Stressed Bodies*

Abstract:
In this talk we discuss the dynamics of continua on differentiable
manifolds. We present a covariant derivation of equations of motion, viewing
motion as a curve in the infinite-dimensional Banach manifold of embeddings
of a body manifold in a space manifold. Our main application is the motion
of residually-stressed elastic bodies; residual stress results from a
geometric incompatibility between body and space manifolds. We then study a
particular example of elastic vibrations of a two- dimensional curved
annulus embedded in a sphere. Based on a joint work with Raz Kupferman and
Reuven Segev.

- Thursday
**March 30**, 14:00, Sari Ghanem (Potsdam):*The decay of SU(2) Yang-Mills fields on the Schwarzschild black hole with spherically symmetric small energy initial data*

Abstract:
First, I will present the Yang-Mills equations on arbitrary fixed curved space-times, valued in the Lie algebra associated to any arbitrary Lie group. Thereafter, I will expose recent results with Dietrich Häfner concerning the Yang-Mills fields valued in the Lie algebra su(2) associated to the Lie group SU(2), propagating on the Schwarzschild black hole. We assume that the initial data are spherically symmetric, satisfying a certain Ansatz and have small energy, which excludes the stationary solutions which do not decay. We then prove uniform decay estimates in the entire exterior region of the black hole, including the event horizon, for gauge invariant norms on the Yang-Mills curvature generated from such initial data, including the $ L^\infty $ norm of the so-called middle components. This is done by proving in this setting, a Morawetz type estimate that is stronger than the one assumed in previous work, without passing through the scalar wave equation on the Yang-Mills curvature, using the Yang-Mills equations
directly.

- Thursday,
**April 6**, 14:00, Juan Valiente-Kroon (Queen Mary):*Non-peeling spacetimes*

Abstract:
In this talk I will give an overview of Friedrich’s construction of a regular asymptotic initial value problem at spatial infinity and the open questions related to it. In particular, I will show how this framework can be used to identify initial data sets for the vacuum Einstein field equations which should lead to spacetimes not satisfying the peeling behaviour. This is research in collaboration with Edgar
Gasperin.

- Thursday,
**April 27**, 14:00, Dennis Raetzel (Vienna):*TBA*

Abstract:
TBA

- Thursday,
**May 4**, 14:00, joint relativity - mathematical physics seminar, Robert Seiringer (ISTA):*The excitation spectrum in a Bose fluid*

Abstract: Of particular relevance for an understanding of the low-temperature properties of a quantum system is the excitation spectrum. With the exception of exactly solvable models in one dimension, rigorous results on its structure are lacking and one has to resort to adhoc approximations to make predictions. We present recent progress on this question for bosonic many-body quantum systems with weak two-body interactions. Such systems are currently of great interest, due to their experimental realization in ultra-cold atomic gases. We investigate the accuracy of the Bogoliubov approximations, which predicts that the low-energy spectrum is made up of sums of elementary excitations, with linear dispersion law at low momentum. The latter property is crucial for the superfluid behavior of the
system.

- Thursday,
**May 11**, 14:00, Katharina Radermacher (Stockholm):*TBA*

Abstract:
TBA

- Thursday,
**May 18**, 14:00, Stefan Hollands (Leipzig):*TBA*

Abstract:
TBA

- Thursday,
**June 22**, 14:00, Carla Cederbaum (Tuebingen):*On extensions of CMC-Bartnik data*

Abstract:
Bartnik data are a Riemannian 2-sphere of positive Gaussian curvature equipped with a non-negative function H to be thought of as its mean curvature in an ambient Riemannian 3-manifold. Mantoulidis and Schoen suggested a construction of asymptotically flat Riemannian 3-manifolds of non-negative scalar curvature which allow to isometrically embed given Bartnik data of vanishing mean curvature, i.e. H=0. They use their construction to explore — and disprove — stability of the Riemannian Penrose inequality. We adapt their construction to constant mean curvature (CMC) Bartnik data, i.e. H=const.>0. I will present the construction as well as the motivation for such a construction which is related to Bartnik’s quasi-local capacity/mass functional and its minimizing
properties.

- Thursday,
**TBA**, 14:00, Michael Eichmair (Vienna):*TBA*

Abstract:
TBA

Location (unless indicated otherwise): Währinger Str. 17

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

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

Gravitational Physics

Faculty of Physics

University of Vienna

Boltzmanngasse 5

1090 Wien

T: +43-1-4277-51501

F: +43-1-4277-9515

Faculty of Physics

University of Vienna

Boltzmanngasse 5

1090 Wien

T: +43-1-4277-51501

F: +43-1-4277-9515