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Calendar of Physics Talks Vienna
| Hidden symmetries in cosmology and black holes |
| Speaker: | Francesco Sartini (ENS Lyon) |
| Abstract: | Cosmological models and black holes belong to classes of space-time metrics defined in terms of a finite number of degrees of freedom, for which the EinsteinâHilbert action reduces to a one-dimensional mechanical model. We investigate their classical symmetries and the algebra of the corresponding Noether charges. These dynamical symmetries have a geometric interpretation, not in terms of spacetime geometry, but in terms of motion on the field space. Moreover, they interplay with the fiducial scales, introduced to regulate the homogenous model, suggesting a relationship with the boundary symmetries of the full theory.
Finally, the existence of these symmetries unravels new aspects of the physics of black holes and cosmology. It opens the way towards a rigorous group quantization of the reduced models, to the study of their holographic properties. It might have significant [...] |
| Date: | Tue, 29.11.2022 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | ZOOM: Join Zoom Meeting https://tuwien.zoom.us/j/96128515992?pwd=V2k0TkNiYXFPM0p1NkE2OW4xODhyUT09 Meeting ID: 961 2851 5992 Password: s7BX7Pvp |
| Contact: | D. Grumiller, S. Fredenhagen, E. Battista, R. Ruzziconi |
| Machine Learning backed Evolutionary Search: Atomic Structure in Surface Reconstructions |
| Speaker: | Ralf Wanzenboeck (TU Wien, Institute of Materials Chemistry) |
| Abstract: | Atomic structure determination of surface reconstructions has typically relied on structural models derived from intuition and domain knowledge. While evolutionarystrategies combined with first-principles computations based on density functional theory have proven powerful tools for structure searches, the computational cost is prohibitive, even on modern hardware. We facilitate the thorough exploration of potential energy landscapes at reasonable cost by combining the efficient covariance matrix adaptation evolution strategy (CMA-ES) with a neural-network force field (NNFF) utilizing Google JAX with just-in-time compilation and end-to-end automatic differentiation.
The first part of the presentation will cover the methodology used for exploring SrTiO3 (110) n°ø 1 overlayer structures and discuss the transferability of the NNFF and the results that were obtained, including known and new |
| Date: | Tue, 29.11.2022 |
| Time: | 16:00 |
| Location: | TU Wien, Institut für Angewandte Physik, E134 1040 Wien, Wiedner HauptstraÃe 8-10 Yellow Tower âBâ, 5th floor, SEM.R. DB gelb 05 B |
| Contact: | Univ.Prof. Dr. Ulrike Diebold |
| Mining Perturbation Theory: Resurgence-Inspired Extrapolation and Analytic Continuation |
| Speaker: | Prof. Gerald V. Dunne (University of Connecticut) |
| Abstract: | What is the best way to extract information from a finite amount of perturbative information? This is a common problem in applications.
We may only be able to compute a (small) finite number of coefficients of an expansion of a function about some special parameter point,
and we wish to learn about the behaviour near another point (possibly very distant).
I will discuss some recent work with Ovidiu Costin using resurgence ideas to address the mathematical question of optimal and near-optimal methods
of analytic continuation, and I will illustrate with several applications in quantum field theory. |
| Date: | Tue, 29.11.2022 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | via zoom https://tuwien.zoom.us/j/96505893692?pwd=TWNKUThEOW83anl1RDl5UDRaZVdNUT09 |
| Contact: | A. Hoang, M. Procura |
| The second law of black hole mechanics in effective field theory |
| Speaker: | Harvey Reall (Cambridge) |
| Abstract: | I shall discuss the second law of black hole mechanics in gravitational theories with higher derivative terms in the action.
Wall has described a method for defining an entropy that satisfies the second law to linear order in perturbations around a stationary black hole.
I shall explain how this can be extended to define an entropy that satisfies the second law to quadratic order in perturbations, provided that
one treats the higher derivative terms in the sense of effective field theory. This talk is based on work with Stefan Hollands and Aron Kovacs. |
| Date: | Thu, 01.12.2022 |
| Time: | 15:15 |
| Duration: | 60 min |
| Location: | by zoom https://tuwien.zoom.us/j/96505893692?pwd=TWNKUThEOW83anl1RDl5UDRaZVdNUT09 |
| Contact: | P. Chrusciel, D. Fajman |
| Did the original SG experiment achieve coherent splitting? |
| Speaker: | Ron Folman (Ben-Gurion University ) |
| Abstract: | The Stern-Gerlach (SG) effect, found a century ago, has become a paradigm of quantum mechanics. Unexpectedly, until recently, there has been little evidence that the original scheme with freely propagating atoms exposed to gradients from macroscopic magnets is a fully coherent quantum process. Several theoretical studies have explained why a SG interferometer (SGI) is a formidable challenge. Here, we provide a detailed account of the realization of a SGI for single atoms. I will review different applications which we have realized with the SGI such as clock interferometry, the measurement of geometrical phase, and the recent observation of a new kind of Moire pattern. This talk may be viewed as a preface to the VCQ colloquium which I will give on the 5th of December, and in which I discuss plans for a SGI for macroscopic objects doped with a single spin. Such a realization would open the |
| Date: | Fri, 02.12.2022 |
| Time: | 10:00 |
| Duration: | 45 min |
| Location: | ATI Hörsaal/https://tuwien.zoom.us/j/93672218922?pwd=dEZNQ2liVzRNNURvNmVWVE5KUWRiQT09 |
| Contact: | Jörg Schmiedmayer |
| Electroweak logarithms in inclusive cross sections |
| Speaker: | Prof. Wouter Waalewijn (University of Amsterdam) |
| Abstract: | I will present a framework to resum electroweak logarithms in inclusive processes, that enables resummation beyond leading logarithmic accuracy.
I will discuss the factorization of the cross section in terms of PDFs and fragmentation functions and, surprisingly, soft functions. They appear because
electroweak corrections to inclusive cross sections involve double logarithms, since the proton is not an electroweak singlet. I will also discuss the
renormalization group equations in some detail, which can be used to carry out the resummation. Due to the chiral nature of the weak force,
the evolution polarizes the distributions. I conclude by discussing extensions to measurements that are neither fully exclusive nor inclusive.
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| Date: | Fri, 02.12.2022 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | Fakultaet fuer Physik, Erwin Schroedinger-HS, Boltzmanngasse 5, 5. Stock |
| Contact: | A. Hoang, M. Procura |
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