Vienna Theory Lunch Seminar, Winter Semester 2024

Tuesdays 12:15-13:30

held alternately at:

TU Wien (TU): Wiedner Hauptstr. 8-10, yellow area, 10th floor, seminar room DB10E11, (how to get there?)

University of Vienna (UV): Boltzmanngasse 5, 5th floor, Schrödinger Lecture Hall

We thank our kind sponsors:

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Idee: Idea:	Im Vienna Theory Lunch Seminar werden aktuelle Themen der Theoretischen Physik, die von DiplomandInnen, DoktorandInnen und PostDocs behandelt werden, aufgegriffen. Das Niveau soll so gewählt werden, dass jeder Student und jede Studentin am Beginn des Masterstudiums dem Vortrag folgen kann. BachelorstudentInnen können besonders von dem Seminar profitieren, da es ihnen ermöglicht einen Eindruck in die Forschungsarbeit beider Universitäten zu erhalten. Die Vortragenden werden dabei auch ermutigt darüber zu sprechen, warum sie ein gewisses Forschungsgebiet gewählt haben. Dabei dürfen durchaus offene Fragen und Probleme behandelt werden und es ist nicht notwendig einen Vortrag über eine "perfekte", abgeschlossene Arbeit zu halten. Damit es zu keinem "Zeitverlust" kommt, wird Mittagessen (Pizza) gratis zur Verfügung gestellt.	The focus of the Vienna Theory Lunch Seminar is on recent research in theoretical Physics done by Master students, PhDs and PostDocs. The seminar is designed for graduate students but should also be comprehensible to advanced undergraduate students. Undergraduate students are particularly encouraged to attend so that they receive an overview of research activities conducted at both universities. Speakers are also encouraged to focus on their motivation for choosing their particular topic and to present open questions. In order to avoid any "loss of time" we provide a free lunch (pizza).
Wie kann ich teilnehmen? How can I join?	Einfach erscheinen! Um per Email informiert zu werden, bitte in die Mailingliste eintragen.	Just attend! To receive informations via email register for the mailing list.

Oct 1, 2024	NO SEMINAR
Oct 8, 2024	NO SEMINAR
Oct 15, 2024	NO SEMINAR
Oct 22, 2024 TU 12:30 - 13:45	Andreas Irmler TU Wien	Computational Solutions to the Many-Body Schrödinger Equation Using High-Performance Computing Despite being studied for over a decade solving the electronic Schroedinger equation exactly for systems with more than a few electrons remains a significant challenge. In this presentation, I will discuss why obtaining sufficiently accurate solutions is inherently complex and why such solutions are still urgently needed. To address this, I will introduce the Coupled Cluster method, a powerful approach that reformulates the problem into an algebraic framework. Additionally, I will demonstrate how the resulting equations can be efficiently solved using supercomputing techniques.
Oct 29, 2024	NO SEMINAR
Nov 5, 2024 TU	Daniel Wieser TU Wien	Single-boson exchange decomposition for the extended Hubbard model with application to the optical conductivity In order to fully capture the effects of strong correlations on condensed matter, it is in principle necessary to solve the many-body Schrödinger equation. Because this is practically impossible for systems larger than a few electrons, numerous methods and approximations have been developed to date. After a short introduction to the Matsubara formalism, I will present two of them, namely the parquet- and the newly developed single-boson exchange decomposition. Subsequently, both approaches are applied to the extended Hubbard model in exact diagonalization to analyze the influence of vertex corrections on the optical conductivity.
Nov 12, 2024 UV	Lin-Qing Chen IQOQI & Uni Wien	Probing Quantum Aspects of Gravitational Fields Recent progress in table-top experiments offers the opportunity to show for the first time that gravity is not compatible with a classical description. However, in all current experimental proposals, such as the generation of gravitationally induced entanglement between two quantum sources of gravity, gravitational effects can be explained with the Newton potential. This is a limitation to the conclusions on the nature of gravity that can be drawn from these experiments. Here, I will introduce a theoretical framework that is suitable for this experimental regime, and we identify two effects that overcome the above-mentioned limitation. First, we show that the phase arising from the interaction between two generic quantum sources of gravity, cannot be reproduced with the Newton potential nor with any limit of (classical) general relativity. Second, we show that the quantum commutator between the gravitational field and its canonically conjugate momentum appears as an additional term in the relative phase of a generic quantum source interacting with a moving test particle. Observing this term in the phase would be a test of the gravitational field as a quantum mediator.
Nov 19, 2024 TU	Ruma Maity TU Wien	Successful training of a triangular swimmer: a genetic algorithm approach Natural microswimmers use various swimming gaits to propel under low Reynolds number conditions in their fluid surrounding for various reasons: search for nutrition, escape from predators or search for prey. A very common strategy for propulsion is the non-reciprocal deformation of the shape of the swimmer in an effort to realize its motion through the medium. In recent times efforts have been made to design artificial swimmers that can successfully mimic their natural counterparts and are thus able to perform specific tasks, such as targeted drug delivery in the case of nanomedical applications. In this work, we train a two-dimensional, triangular swimmer to move in a desired direction and to detect in an efficient manner nutrition sources.
Nov 26, 2024	NO SEMINAR
Dez 3, 2024 TU	Helmut Hörner TU Wien	Python Library for Simulating Optical Systems, Cavities and Ring Cavities In my talk I present a Python library I’ve developed that facilitates the simulation of optical light propagation, optical cavities, and optical ring cavities (in the classical domain). The software tool is designed to enhance the ability to model and analyze these systems with great efficiency and minimal effort on your personal PC as well as on the VSC cluster. It offers a wide range of “components” out of the box, including partially and totally reflective plane and curved mirrors, lenses, apertures, absorbers, beam-splitters, and various light sources.
Dez 10, 2024 UV	Garance Lankester and Stefan Daniel Nellen Mondragon University of Vienna, ÖAW	Dark Matter Signal from Atomic to Galactic Scales Despite extensive observational evidence, the true nature of Dark Matter (DM) remains one of the most persistent mysteries in modern physics. A key challenge lies in DM's weak interaction with ordinary matter, which results in subtle and difficult-to-detect signals. This talk will provide a comprehensive overview of the current understanding of DM, from its historical foundations to the latest advancements in both direct and indirect detection methods. At the galactic scale, we will focus on the implications of Self-Interacting Dark Matter (SIDM) in addressing the small-scale structure problem. Additionally, we will explore how phenomena intrinsic to matter, such as the Migdal effect, can significantly enhance the sensitivity of direct detection experiments, potentially unlocking new avenues for observing DM.
Dez 17, 2024 TU	Max Riegler	An Introduction to Quantum Key Distribution and Numerical Security Proofs Quantum Key Distribution (QKD) offers a novel approach to secure communication, leveraging the laws of quantum mechanics. This talk will introduce the fundamental principles behind QKD and highlight its unique advantages. We will explore how numerical methods are used to rigorously certify the security of QKD systems, even in the presence of practical imperfections in hardware and implementation. By combining concepts from physics, information theory, and optimization, these security proofs bridge the gap between theory and real-world applications.
Dez 24, 2024	NO SEMINAR
Dez 31, 2024	NO SEMINAR
Jan 7, 2025	NO SEMINAR
Jan 14, 2025 TU	Philipp Neckam TU Wien	Higher-Spin Gravity in Three-Dimensional Flat Space Theories of interacting massless fields of spin larger than two naturally emerge in the high-energy limit of string theory. When including gravity, these theories also serve as toy models to investigate the holographic AdS/CFT correspondence in a more controlled setting. While it has long been known that the existence of such theories is strongly restricted by various no go theorems, in three dimensions none of these results apply, thus providing an ideal setting to study higher-spin gravity. Even so, the investigation of three-dimensional metric-like higher-spin gravity theories has been initiated only recently in 2018, and the work discussed here is a continuation of these efforts. The Noether-procedure is generalized to three dimensions, taking into account the influence of dimension-dependent-identities. Starting from cubic interaction vertices, the induced deformations of the gauge transformations as well as the resulting gauge brackets are then determined at first order. The consistency of these methods is demonstrated for the example of spin-3-gravity by verifying the Jacobi-identity as well as the closure of the gauge algebra. The coupling of matter to the higher-spin fields is also investigated.
Jan 21, 2025 UV	Robert Tiefenbacher University of Vienna	Family of Weyl-algebras and the Carrollian limit Carrollian field theories arise from the idea of letting c go to 0. The interest in such bizarre field theories comes first of all from the fact that the result is not nonsensical and the connection to flat space holography and tachyons. We show a different approach to Carroll theories, where we scale a regular complex scalar field in such a way as to reproduce a Carroll theory in the limit. This allows us to construct a family of Weyl-algebras associated to the scaled complex fields and "limit" algebra.
Jan 28, 2025	TBA

Vienna Theory Lunch Seminar

Tuesdays 12:15-13:30

Google Calender for the Seminar