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Calendar of Physics Talks Vienna
| Conformal Carrollian Field Theories on null Manifolds |
| Speaker: | Poulami Nandi (TU Wien, IIT Kanpur) |
| Abstract: | Conformal Carrollian groups are known to be isomorphic to Bondi-Metzner-Sachs (BMS) groups that arise as the symmetries of the field theories defined on null manifolds. We construct explicit examples of Conformal Carrollian field theories (CCFTs) as Ultra Relativistic limits of relativistic conformal theories where even in dimensions d = 4, there is an infinite enhancement of the underlying symmetry structure. Then, we propose an action for a simple interacting CCFT viz. Carrollian scalar electrodynamics using the Helmholtz conditions. This action is the first example for an interacting CCFT. We show that the proposed action respects the finite and infinite conformal Carrollian symmetries in d = 4. The Poisson brackets for the corresponding conserved charges confirm that infinite Carrollian conformal algebra is satisfied even at the level of charges. |
| Date: | Tue, 14.01.2020 |
| Time: | 13:45 |
| Duration: | 60 min |
| Location: | TU Wien - Wiedner Hauptstraße 8 - Red Area, 7th floor, Seminar Room (DC 07 A15) |
| Contact: | S. Fredenhagen, D. Grumiller |
| Shedding Light on Isobars |
| Speaker: | Prof. Robin Golser (University of Vienna, Faculty of Physics, Isotope Physics) |
| Abstract: | Accelerator Mass Spectrometry (AMS) is an extremely sensitive method to measure minute amounts of matter. Abundance sensitivities can be as low as 1E-16 even in the presence of an enormous background many orders of magnitude more intense. Measuring at such low levels makes most sense for unstable isotopes since their presence can only be due to ongoing production processes. An electrostatic accelerator of the Tandem type is utilized to break-up interfering molecules and to provide sufficient energy to identify the isotopes of interest by their nuclear charge at MeV energies. Stable isobars, i.e. stable isotopes with almost the same mass as the radio-isotope of interest, are the challenge in (A)MS. Exploiting electronic properties of the isobaric anions at eV kinetic energies is becoming a breakthrough for isobar suppression... [complete abstract https://indico.smi.oeaw.ac.at/event/354/] |
| Date: | Wed, 15.01.2020 |
| Time: | 17:00 |
| Duration: | 60 min |
| Location: | Stefan-Meyer-Institut, Boltzmanngasse 3, 1090 Wien, Seminarraum 3-2-08 (2. Stock) |
| Contact: | Prof. Dr. Eberhard Widmann, Dr. Martin Simon |
| Marginally trapped surfaces |
| Speaker: | Walter Simon (Vienna) |
| Abstract: | A marginally trapped surface (MTS) is a compact two-surface in spacetime such that
(at least) one of the two families of orthogonally emanating null geodesics has vanishing expansion. Compared to related concepts like trapped surface, apparent horizon, etc.,
a MTS is the least restrictive key ingredient in results on black hole formation and -merger, as well as for singularity formation in General Relativity.
The mathematical analysis of MTSs involves differential geometry, bifurcation analysis, and elliptic theory applied to quasilinear equations, in particular Jang’s equation.
We give simple examples of spacetimes with and without MTS, quote mathematical results, prove a few simple ones, expose their role in black hole physics mentioned above, and compare with recent numerical simulations.
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| Date: | Thu, 16.01.2020 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Arbeitsgruppe Gravitation, Währinger Strasse 17, Raum 218, 2. Stock, 1090 Wien |
| Contact: | P.T. Chrusciel, D. Fajman |
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