# Current seminars

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

Currently (unless indicated otherwise) all seminars are held via ZOOM.

The Mathematical Physics Seminars take place on Tuesdays at 13.45.

The Particle Physics Seminars take place on Tuesdays at 16.15.

- Thursday,
**May 5th, 15:00 online via ZOOM**

Lavinia Heisenberg (ETH Zurich): The geometrical manifestation of gravity

Abstract: General Relativity and the Cosmological Principle are the fundamental pillars of Cosmology. After introducing them and their underlying properties I will discuss the successes and challenges of the Standard Model of Big Bang Cosmology. I will then discuss how we can test General Relativity using different cosmological observations, from its geometrical properties down to testing the involved propagating degrees of freedom. This analysis will also help us to classify the attempts of going beyond General Relativity together with their explicit implications.

- Thursday,
**May 12th, 15:00 Seminarraum A**

Patryk Mach (Cracow): Collisionless Vlasov gas around black holes

Abstract: I will discuss accretion of collisionless Vlasov gas onto a Schwarzschild black hole. An equivalent of the Bondi flow (steady spherically symmetric accretion) has been developed by Paola Rioseco and Olivier Sarbach in 2017. In this case, the gas is assumed to be at rest at infinity, where it is described by the Maxwell-Juttner distribution. Last year, together with Andrzej Odrzywołek, we computed an equivalent of the so-called Bondi-Hoyle model (accretion onto a moving black hole). I will discuss some details of this model and compare them to the results obtained in the ballistic approximation. If time permits, I will comment on possible generalizations to the Kerr geometry

- Tuesday,
**May 17th, 13:00 Lunch Seminar**

Thomas Spanner (Vienna): Response of an interferometer mounted on an elastic quadratic plate to gravitational waves

Abstract: LIGO uses kilometre long tunnels and freely suspended mirrors as an interferometer to detect gravitational waves. I discuss what would happen if the interferometer were placed on an elastic plate in a laboratory instead. The behaviour of the plate under the influence of a gravitational wave is described by the relativistic Theory of Elasticity as formulated by Beig and Schmidt. To solve the equations of motion for the deformation a spectral approach is developed, which considers the discontinuities at the boundaries, which appear when using a Fourier Series to express nonperiodic functions and their derivatives.

- Thursday,
**May 19th, 15:00 Seminarraum A**

Christian Spreitzer (Vienna): Spin interaction of neutrons with an intensive laser pulse

Abstract: We study the Dirac equation for neutral particles with a magnetic moment in the field of an ultrashort electromagnetic pulse. The pulse is modeled as a delta-distribution, concentrated on a null (i.e. lightlike) hyperplane. We show that the solutions can be obtained by "gluing" free solutions along the pulse and derive corresponding matching conditions. For the special case of a homogeneous electromagnetic pulse, i.e. constant field strength, we explicitly calculate the change in the spin orientation. This is joint work with Peter C. Aichelburg and Herbert Balasin.

- Thursday,
**June 9th, 15:00 Seminarraum A**

Anton Rebhan (TU Wien): Gauge/gravity duality and the anomalous magnetic moment of the muon

Abstract: Currently there is a discrepancy between the Standard Model prediction for the anomalous magnetic moment of the muon and the experimental value above 4 standard deviations according to the Muon g-2 Theory Initiative White Paper. With further experimental improvements expected in the near future, it is imperative to further sharpen the theoretical prediction which is limited by uncertainties of QCD contributions. I describe the recent progress made in using gauge/gravity duality ("holographic QCD") to study hadronic contributions to the anomalous magnetic moment of the muon, in particular the hadronic light-by-light scattering contribution, where the short-distance constraints associated with the axial anomaly are notoriously difficult to satisfy in hadronic models but are implemented naturally in simple ("bottom-up") holographic QCD models.

- Friday,
**June 24th, 13:00 Seminarraum A**

Herbert Balasin (TU Wien):

Abstract: