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Calendar of Physics Talks Vienna
| Gravitational memory effects for particles and wave packets (Vienna Theory Lunch Seminar) |
| Speaker: | Marius Oancea (Universität Wien) |
| Abstract: |
Gravitational waves can generally influence the dynamics of test objects with which they interact. Changes in the relative dynamics of test objects can persist even after the gravitational wave has passed and spacetime is again flat. These are generally referred to as gravitational memory effects, since the properties of the passing gravitational wave remain encoded in the relative dynamics of test objects. In this talk, I will discuss gravitational memory effects in plane wave spacetimes for different classes of test objects: particles following geodesics, spinning particles with non-geodesic motion, and test scalar fields. For all these objects, memory effects are encoded into a set of four memory tensors that depend on the gravitational wave profile. Joint work with Abraham Harte, Thomas Mieling, and Florian Steininger.
[[part of https://lunch-seminar.univie.ac.at ]] |
| Date: | Tue, 07.05.2024 |
| Time: | 12:30 |
| Duration: | 75 min |
| Location: | TU Wien: Wiedner Hauptstr. 8-10, yellow area, 10th floor, seminar room DB10E11 |
| Contact: | Florian Lindenbauer |
| Higgs Branch RG-flows â Decay and Fission of Magnetic Quivers |
| Speaker: | Marcus Sperling (University of Vienna) |
| Abstract: | Supersymmetric theories with 8 supercharges in dimensions 3 through 6 have a large moduli space of vacua, and the Higgs branches are one of the most significant parts of this space. These (singular) hyper-Kahler spaces can be characterised by a combinatorial object known as the magnetic quiver. By using this technique, we can fully encode the Higgs branch geometry for both the low energy effective description and the strongly coupled conformal fixed point.
Here, I present the decay and fission algorithm for unitary magnetic quivers. It efficiently derives complete phase diagrams (Hasse diagrams) through convex linear algebra.It allows magnetic quivers to undergo decay or fission, reflecting Higgs branch RG-flows in the theory.
In this talk, I will discuss this construction in the context of 5d and 6d theories.
Based on arXiv:2312.05304 and 2401.08757 with A. Bourget and Z. Zhong. |
| Date: | Tue, 07.05.2024 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Erwin-Schrödinger-Hoersaal, 1090 Vienna, Boltzmanngasse 5, 5th floor |
| Contact: | S. Fredenhagen |
| Electron emission studies and surface technologies for particle accelerators |
| Speaker: | Marcel Himmerlich (Cern/Switzerland) |
| Abstract: | The maximum achievable intensity in a particle accelerator such as the Large Hadron Collider (LHC) is strongly dependent on a resonant phenomenon called electron cloud formation, which is linked to the generation of secondary electrons at the material surfaces that are directly facing the proton beam. The High-Luminosity LHC project has the goal to increase the luminosity of the collider by a factor of 10 compared to its original design from 2029 onward. To achieve this goal, many different technical solutions are currently being developed at CERN and at partner institutions, including technologies to mitigate electron cloud formation in critical components of the machine. Two main ingredients are relevant for pushing the limits of the surface technology for large-scale vacuum systems: 1. the development of methods that modify the surface properties and that can be either applied in alre |
| Date: | Tue, 07.05.2024 |
| Time: | 16:00 |
| Duration: | 40 min |
| 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: | Prof. Dr. wolfgang Werner |
| Cosmic rays in jets of Active Galactic Nuclei |
| Speaker: | Anita Reimer (University of Innsbruck) |
| Abstract: | Gamma rays, high-energy neutrinos and cosmic rays impinging on Earth signal the existence of environments in the Universe that allow acceleration of particle populations into the extremely energetic regime. Jets of Active Galactic Nuclei (AGN) - powerful relativistic matter streams emanating from the core of distant galaxies that host supermassive black holes - are among the most numerous persistent source populations in the high-energy gamma-ray sky, and are considered prime candidate sources of the ultra-high-energy cosmic rays (UHECRs) observed on Earth.
In this presentation I will discuss aspects of the survival, workings, possible signatures and role of UHECRs in various environments that jets of AGN offer. |
| Date: | Tue, 07.05.2024 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | Erwin-Schroedinger-Hoersaal, Boltzmanngasse 5, 5. Stock |
| Contact: | S. Plaetzer |
| Entering the metal age: Towards high thermoelectric performance via interband scattering |
| Speaker: | Fabian Garmroudi (TU Wien, Institute of Solid State Physics) |
| Abstract: | Thermoelectric (TE) materials hold high hopes for various important applications such as converting waste heat into electricity or targeted and efficient cooling. Although historically, the TE effect was first discovered in simple metals more than 200 years ago, researchers nowadays focus on highly complex semiconductors. Here, the primary focus lies on reducing the lattice thermal conductivity κ_l down to the amorphous limit via different approaches. However, as a downside, crystallographic and chemical features yielding ultralow κ_l often go hand in hand with poor structural, mechanical and thermal stability.
The stringent requirement to reduce κ_l does not apply to good metallic conductors (like Cu) which often show electron-dominated instead of lattice-dominated heat transport. In such systems, the dimensionless figure of merit zT, which determines the efficiency of TE devices, sole |
| Date: | Tue, 07.05.2024 |
| Time: | 16:40 |
| Duration: | 15 min |
| 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. Markus Valtiner |
| Erwin Schrödinger Lecture: Ice clouds over the Asian monsoon and their role in the global climate/ CANCELLED 6.5.24 |
| Speaker: | Martina Krämer (University of Mainz) (CANCELLED 06.05.2024) |
| Abstract: | The Asian Summer Monsoon is the most pronounced atmospheric weather system during boreal summer, consisting of a large-scale anticyclone extending from Asia to the Middle East. Moist air masses are transported via strong convection or general tropical upwelling to altitudes where the coldest temperatures in the atmosphere are found. The ice clouds over the Asian monsoon can have either a warming or a cooling effect. Also, they affect the amount of water vapour in the tropical upper troposphere. Understanding the overall effect of ice clouds on this chain of processes is a focus of recent research. Here, unique aircraft-based observations of ice clouds and water vapour over the Asian monsoon are presented. In particular, ice cloud properties, formation and evolution will be shown and investigated based on simulations. |
| Date: | Tue, 07.05.2024 |
| Time: | 17:00 |
| Duration: | 60 min |
| Location: | Erwin Schrödinger Institute, Boltzmann Lecture Hall, Boltzmanngasse 9, 1090 Wien |
| Contact: | Erwin Schrödinger Institute, University of Vienna |
| Initial data sets with vanishing mass are contained in pp-waves. |
| Speaker: | Seven Hirsch (IAS) |
| Abstract: | Abstract: Isolated gravitational systems such as stars, galaxies and black holes are modeled by asymptotically flat initial data sets. In 1981 Schoen-Yau and Witten showed that such initial data sets with vanishing energy must be contained in Minkowski space. We show that if such initial data sets have vanishing mass, they must be contained in pp-wave spacetimes. This is based upon joint work with Yiyue Zhang from UCI. |
| Date: | Wed, 08.05.2024 |
| Time: | 13:45 |
| Duration: | 60 min |
| Location: | via zoom |
| Contact: | Piotr T. Chrusciel |
| Autonomous Quantum Processing Unit: Constructing a thermodynamically self-contained model of quantum computation |
| Speaker: | Florian Meier (TU Wien, Atominstitut) |
| Abstract: | In this seminar, we investigate the question: "Can we build a physical model for quantum computation that is fully autonomous?", by envisaging a quantum machine where the program to be executed as well as the control are both quantum. We do so by developing a framework that we dub the autonomous Quantum Processing Unit (aQPU). This machine, consisting of a timekeeping mechanism, instruction register and computational system allows an agent to input their problem and receive the solution as an output, autonomously. Using the theory of open quantum systems and results from the field of quantum clocks we can model the thermodynamic cost of computation, including the contributions coming from the control. We find that inputting only finite thermodynamic resources leads to imperfect computation, and that perfect precision for the computation requires divergent thermodynamic resources.
Prepri |
| Date: | Wed, 08.05.2024 |
| Time: | 16:15 |
| Duration: | 45 min |
| Location: | Helmut Rauch Hörsaal ATI |
| Contact: | Maximilian Prüfer |
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