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Calendar of Physics Talks Vienna
| Number theoretic aspects of black hole entropy in 4d string compactification |
| Speaker: | Abhiram Kidambi (TU Wien) |
| Abstract: | In this talk, We shall look at the relation between the dyon (black hole) counting prescription in N = 4, d = 4 string theory from a macroscopic and microscopic point of view and the underlying number theoretic/algebro-geometric framework. From the macroscopic perspective for N = 4 theories, these dyonic BH degeneracies are extracted via the localization technique in N = 2 superconformal gravity while from the microscopic theory, these degeneracies are encoded in the Fourier expansion of certain automorphic forms. For the case of N = 4 in which a subset of the quarter BPS dyons are prone to wall crossing, there is a number theoretic prescription for capturing the exact dyon/BH degeneracies of those quarter BPS states that do not decay via a Jacobi-Fourier decomposition and the Hardy-Ramanujan-Rademacher circle method. However,we shall see that for an exact match of degeneracies,there ... |
| Date: | Tue, 04.12.2018 |
| Time: | 13:45 |
| Duration: | 60 min |
| Location: | Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock |
| Contact: | S. Fredenhagen, D. Grumiller |
| Fe¬3O4 (001) as a model system for single-atom catalysis |
| Speaker: | Jan Hulva (TU Wien, Institut für Angewandte Physik) |
| Abstract: | The rapidly emerging field of “single-atom catalysis” aims to drastically reduce the amount of precious metal required to catalyze chemical reactions by replacing nanoparticles with single-atom active sites. Although there are now many reports of active single-atom catalysts [1], the concept itself remains controversial because it is challenging to characterize real catalysts and determine the reaction mechanism. In our work, we study fundamental properties of supported single metal atoms using a surface science approach. We employ the Fe3O4 (001) surface as a model support, because it can stabilize dense arrays of single metal atoms to temperatures as high as 700 K [2,3].
In this talk, I will present a few examples of Me1/Fe3O4(001) systems and discuss how the coordination of the adatoms influences their adsorption properties. Next, I will focus on the reactivity of the Pt species and s |
| Date: | Tue, 04.12.2018 |
| Time: | 16:00 |
| Location: | TU Wien, Institut für Angewandte Physik, E134 1040 Wien, Wiedner Hauptstraße 8-10 Yellow Tower „B“, 5th floor, SEM.R. DB gelb 05 B |
| Contact: | Univ.Prof. Dr. Ulrike Diebold |
| Magnetic nanostructures in metastable fcc Fe thin films on Si(100) |
| Speaker: | Jonas Gloss (TU Wien, Institut für Angewandte Physik) |
| Abstract: | It has been shown that 5-10 ML thick Fe films grown on Cu(100) single crystal have an fcc structure and are nonmagnetic at room temperature [1]. Ion-beam irradiation of the fcc films causes a structural transformation from fcc to bcc, as well as a magnetic transformation from non- to ferromagnetic. To remove the 10-ML thickness limit of fcc Fe we alloyed it with 22% of nickel to form a metastable fcc Fe78Ni22 [2] and used this system for fabrication of a magnonic crystal [3].
To avoid the costly Cu single crystals, we also grew the films on H-terminated Si(100) with a Cu(100) buffer layer. The H-Si was prepared both in-situ by flashing and deposition of atomic H and ex-situ by etching in HF. The as-grown Fe78Ni22 films were corrugated yet metastable; we show they provide the opportunity to write magnetic nanostructures with a focused ion beam [4].
[1] A.Biedermann, et al., Phys. Rev. |
| Date: | Tue, 04.12.2018 |
| Time: | 16:00 |
| Location: | TU Wien, Institut für Angewandte Physik, E134 1040 Wien, Wiedner Hauptstraße 8-10 Yellow Tower „B“, 5th floor, SEM.R. DB gelb 05 B |
| Contact: | Univ.Prof. Dr. Ulrike Diebold |
| Invariants for QCD algebra |
| Speaker: | Malin Sjödahl (Univ. Lund, Schweden) |
| Abstract: | im Rahmen des Teilchenphysikseminars: Calculations involving the SU(3) structure of QCD are typically performed using so-called trace bases or color flow bases for decomposing color structure. While these spanning sets have some simplifying properties, the fact that they are overcomplete and non-orthogonal becomes a major obstacle for calculations involving many partons. In this talk I will describe how to use group invariants to perform color space calculations instead, and I will argue that this --- once a sufficient set of invariants and an efficient implementation is at hand --- may well be superior. |
| Date: | Tue, 04.12.2018 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock |
| Contact: | A. Hoang, S. Plätzer, M. Procura |
| Extension of the J-PARC Hardron experimental facility - summary report |
| Speaker: | Prof. Hiroaki Ohnishi (Research Center for Electron Photon Science (ELPH), Tohoku University) |
| Abstract: | Dynamics of elementary particles, such as quarks and gluons, are well described by the theory of the strong interaction, i.e. Quark Chromodynamics (QCD). In our universe, many varieties of matters are created by strong interaction, e.g. proton, neutron, nucleus and even neutron stars which has supper high density matter in it. However, due to the non-perturbative nature of the QCD at low energy regime, it is very hard to construct those matters directly from QCD itself. To date, lattice QCD succeeded to construct ground state baryon masses at the point where quark mass is very close to physical point, however excited hadrons are not. Thus Hadron spectroscopy and investigation of hadron-hadron interaction will be a way to reveal the information of nature in low energy QCD. One of the keys... [full abstract available here: https://indico.smi.oeaw.ac.at/event/304/] |
| Date: | Wed, 05.12.2018 |
| 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 |
| Optimal transport and the Einstein equations |
| Speaker: | Stefan Suhr (Ruhr-Uni Bochum) |
| Abstract: | Im Rahmen des Literaturseminars für Gravitationsphysik: The Ricci curvature is the basic ingredient in the Einstein equations of general relativity.
In recent years the interpretation of Ricci curvature in Riemannian geometry has changed fundamentally via its characterization in terms of convexity properties of e.g. the Shannon-Bolzmann entropy of optimal transportation. In my talk I will explain the recent development of an analogous characterization of Ricci curvature in Lorentzian geometry.
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| Date: | Thu, 06.12.2018 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Arbeitsgruppe Gravitation, Währinger Strasse 17, Raum 218, 2. Stock, 1090 Wien |
| Contact: | P.T. Chrusciel, D. Fajman |
| Erwin Schrödinger Lecture: Dynamic Graph Algorithms: A Survey |
| Speaker: | Monika Henzinger (University of Vienna) |
| Abstract: | Real-world graphs are huge and many of them change dynamically. Thus to compute properties of these graphs we need dynamic graph algorithms that efficiently maintain properties of dynamically changing graphs. We present the state-of-the-art in dynamic graph algorithms and explain some of the techniques that they use as well as recent progress in giving lower bounds for their running time.
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| Date: | Thu, 06.12.2018 |
| Time: | 17:00 |
| Duration: | 60 min |
| Location: | ESI, Boltzmanngasse 9, 1090 Wien, Top Floor, Boltzmann Lecture Hall |
| Contact: | ESI, secr@esi.ac.at |
| Matter wave interferometry for inertial sensing and tests of fundamental physics |
| Speaker: | Dennis Schlippert (Universität Hannover) |
| Abstract: | Today's state-of-the-art atom inertial sensors require improvements in stability and accuracy in order to fully exploit their potential with large scale factors on very long baselines on ground and in space, as well as in dynamic environments, e.g. for inertial navigation. We report on recent developments concerning the commissioning of the Very Long Baseline Atom Interferometry test stand. Stretching over 15m, the facility with its high-performance magnetic shield, Rb-Yb atom sources, and a low-frequency seismic attenuation system, will allow us to take on the competition with the stability of superconducting gravimeters with absolute measurements. By operating in a differential mode, we anticipate tests of the Universality of Free Fall at levels of parts in 10^13 and below.
We will furthermore report on matter wave sensors enhanced with opto-mechanical resonators as well as fully guided interferometry and discuss the potential of such systems in inertial sensing and fundamental physics.
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| Date: | Fri, 07.12.2018 |
| Time: | 15:30 |
| Location: | Atominstitut, Hörsaal, Stadionallee 2, Wien 2 |
| Contact: | P. Haslinger |
| Unravelling the mystery of dark matter in the light of experimental results |
| Speaker: | Suchita Kulkarni (HEPHY Wien) |
| Abstract: | im Rahmen des Teilchenphysikseminars |
| Date: | Fri, 07.12.2018 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock |
| Contact: | A. Hoang, S. Plätzer |
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