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Calendar of Physics Talks Vienna
| Higher-form symmetries and how to gauge them |
| Speaker: | Benjamin Haake (University of Edinburgh) |
| Abstract: | I will give a general introduction to higher-form symmetries and their gauging and discuss both of these in the context of defect TQFTs.
Following the insight that ordinary, group-like global symmetries can be described by topological codimension 1 defects, higher-form symmetries are the generalization to arbitrary codimension. A natural question is how to gauge (higher-form) symmetries from this perspective. I will briefly motivate the orbifold construction as a tool for gauging and present a new construction that produces a candidate orbifold datum from 2-group symmetries in 3d. Lastly, I will use this construction to recover a known class of orbifold data from a 0-form symmetry and show how its gauging can be undone by the gauging of an emergent 1-form symmetry.
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| Date: | Tue, 08.04.2025 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Erwin-Schroedinger-HS, Boltzmanngasse 5, 1090 Wien, 5.Stock |
| Contact: | S. Fredenhagen, M. Sperling |
| ViPErLEED and Parameter Tree Based Tensor-LEED |
| Speaker: | Alexander Imre (TU Wien, IAP, FB Oberflächenphysik) |
| Abstract: | Quantitative Low-Energy Electron Diffraction [LEED-I(V)] is a powerful technique for determining atomic-scale surface structures, crucial for understanding surface chemistry, catalysis, and material properties. In LEED-I(V), diffraction intensities measured as a function of incident electron energy are compared directly and quantitatively to theoretical calculations.
Over recent years, we have developed ViPErLEED, a comprehensive and user-friendly software package designed to streamline LEED-I(V) analyses. ViPErLEED integrates experimental-data processing, robust theoretical modeling, and advanced optimization routines into a single accessible environment. Here, we provide an overview of ViPErLEEDâs key features and typical use cases, followed by a discussion of ongoing developments.
A primary focus of our current efforts is improving structural optimization methods, the computational bo |
| Date: | Tue, 08.04.2025 |
| 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 zoom-link: https://tuwien.zoom.us/j/94889135245?pwd=OEYxYi96L2hRL0lp |
| Contact: | Prof. G. Parkinsom |
| Silver iodide â surface structure and ice nucleation investigated by noncontact AFM |
| Speaker: | Johanna Hütner (TU Wien, IAP, FB Oberflächenphysik) |
| Abstract: | Silver iodide (AgI) is used as an efficient cloud seeding agent due to its good lattice match with hexagonal ice. However, the basal AgI surfaces are polar and thus inherently unstable. The mechanism for polarity compensation requires surface modifications, which may disrupt the epitaxial relationship with hexagonal ice.
Atomically resolved noncontact atomic force microscopy (NC-AFM) images reveal that AgI basal planes undergo surface reconstuctions to compensate polarity. The Ag-terminated surface forms a (2 Ã 2) reconstruction with hexagonal symmetry, whereas the I-terminated surface adopts a complex reconstruction with rectangular symmetry. Upon exposure to water vapor at 100 K in UHV, ice growth occurs in different modes on the two terminations. An epitaxial ice layer forms only on the Ag-terminated surface, whereas the reconstruction of the I-terminated surface prevents epitaxial ic |
| Date: | Tue, 08.04.2025 |
| 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 zoom-link: https://tuwien.zoom.us/j/94889135245?pwd=OEYxYi96L2hRL0lp |
| Contact: | Prof. G. Parkinsom |
| Walking in the Hidden Valley: Exploring dark parton showers in the conformal window |
| Speaker: | Joshua Lockyer (University of Graz) |
| Abstract: | Dark-showers offer a compelling collider signature for Hidden Valley models featuring a confining dark sector. Our work extends these investigations to models with many more dark quark flavours where such theories enter the âconformal window''. Here, existing running coupling approximations in current event generators break down and so we must implement the exact two-loop RGE solution. This, alongside the two-loop Sudakov factor that employs this coupling, allows us to present the first phenomenological results of the parton showers of such near-conformal dark sectors. |
| Date: | Tue, 08.04.2025 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | Erwin-Schroedinger-HS, Boltzmanngasse 5, 1090 Wien, 5.Stock |
| Contact: | A. Hoang, M. Procura |
| Global critical points of the Standard Model on expanding spacetimes |
| Speaker: | Marko Sobak (University of Vienna) |
| Abstract: | The Standard Model (SM) is one of the greatest successes of modern theoretical physics. Despite this, mathematical references studying the full SM (rather than just its sectors in isolation) on curved spacetimes are somewhat scarce, even though it seems important to understand the theory at a classical level in a more geometric setting. In my talk, I will first briefly review the mathematical structure of the SM Lagrangian, the corresponding Euler-Lagrange equations, and some of their basic properties, particularly related to conformality. Then, I will present a global existence result for the SM equations on four-dimensional spacetimes of expanding type. The talk is focused on a geometrically intrinsic approach to the theory, and the main ingredient for the proof is a gauge-invariant energy estimate.
This is joint work with Volker Branding.
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| Date: | Wed, 09.04.2025 |
| Time: | 14:15 |
| Duration: | 60 min |
| Location: | Seminar Room A, Waehringer Str. 17, 1090 Wien, 2nd floor |
| Contact: | D. Fajman |
| Optical excitation and stabilization of ultracold field-linked tetratomic molecules |
| Speaker: | Bijit Mukherjee (University of Warsaw) |
| Abstract: | Trapped samples of ultracold molecules often short-lived because close collisions between them result in trap loss. To mitigate such loss, shielding methods [1, 2] have been extensively developed and have recently been successfully implemented [3-5]. Shielding is achieved by external static electric fields or near-resonant microwaves. The external field responsible for shielding also allows creation of weakly bound ultracold tetratomic molecules (âtetramersâ). Recently, such tetramers have been realized from pairs of ultracold alkali-metal diatoms using an external microwave field [6]. These tetramers are termed field-linked (FL) molecules as an external field is necessary to create them.
The motivation of this work is to develop a methodology to create deeper bound tetramers starting from the loosely bound FL tetramers. We envisage extending the tools for photoassociation of ultracold |
| Date: | Wed, 09.04.2025 |
| Time: | 16:15 |
| Duration: | 45 min |
| Location: | Helmut Rauch Hörsaal ATI |
| Contact: | Maximilian Prüfer |
| Harnessing complexity to manipulate quantum light in space and time |
| Speaker: | Mehul Malik (Henriot Watt University) |
| Abstract: | High-dimensional quantum states of light, such as photons entangled in their spatial or temporal structure, can carry significantly more information than qubits. Also known as âqudits,â such states offer the potential for noise-robust and high-capacity quantum communication networks [1]. A central challenge in the realisation of such networks is the ability to precisely control and measure photonic qudits. In this talk, I will show how we can harness complex scattering processes inside a commercial multi-mode fiber to program arbitrary quantum circuits and measurements for photonic qudits encoded in space and time. First, I will present our âtop-downâ approach where a smaller unitary transformation is embedded inside the larger modal space of the fiber, with the auxiliary modes serving as an additional resource. I will demonstrate how this capability allows us to turn the multi-mode fibr |
| Date: | Fri, 11.04.2025 |
| Time: | 10:00 |
| Duration: | 45 min |
| Location: | Helmut Rauch Hörsaal ATI |
| Contact: | Marcus Huber |
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