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Calendar of Physics Talks Vienna
| Scaling properties of RNA as a branched polymer |
| Speaker: | Anze Bosic (Department of Theoretical Physics, Josef Stefan Institute, Ljubljana, Slovenia) |
| Abstract: | Formation of base pairs between the nucleotides of an RNA sequence gives rise to a complex and often highly branched RNA structure. While numerous studies demonstrated the functional importance of the high degree of RNA branching - for instance, for its spatial compactness or interaction with other biological macromolecules - RNA branching topology remains largely unexplored. We use the theory of randomly branching polymers to explore the scaling properties of RNAs by mapping their secondary structures onto planar tree graphs. Focusing on random RNA sequences of varying lengths, we determine the two scaling exponents related to their topology of branching. By understanding the scaling properties of RNA related to its branching structure we aim to improve our understanding of the underlying principles and open up the possibility to design RNA sequences with desired topological properties. |
| Date: | Tue, 20.06.2023 |
| Time: | 10:00 |
| Duration: | 45 min |
| Location: | Seminarraum DB gelb 03 |
| Contact: | Emanuela Bianchi |
| Modifying General Relativity using Topological Terms |
| Speaker: | Francesco Bajardi (Scuola Superiore Meridionale) |
| Abstract: | Despite the success and the formal elegance, general relativity suffers from shortcomings at any scale of energy. For this reason, several alternatives have been proposed over the years, with the aim to address issues provided by Einstein's gravity. Within the plethora of modified theories of gravity, particular interest is gained by modifications including topological invariants, such as the Gauss-Bonnet term. Extending the gravitational action with the Gauss-Bonnet invariant leads to interesting dynamics in cosmological and spherically symmetric backgrounds. Specifically, the early and late-time Universe bahaviours can be predicted without invoking any Dark Energy, which is thus mimicked by geometric contributions.Moreover,considering the Gauss-Bonnet term into the action can settle theoretical issues, currently faced by General Relativity. After selecting the form of the action . . . |
| Date: | Tue, 20.06.2023 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | TU Wien, Sem.R. DA gruen 05 (Freihaus, TU Wien, Wiedner Hauptstrasse 8) |
| Contact: | S. Fredenhagen, D. Grumiller, E. Battista, R. Ruzziconi |
| IBP Reduction with Groebner bases |
| Speaker: | Robin Brueser (Universitaet Freiburg) |
| Abstract: | In this talk we investigate how Groebner bases theory can be used to perform integration-by-parts (IBP) reductions of loop integrals.
The first part of the talk serves as brief introduction to IBP reduction and Groebner bases.
In the second part we discuss the main idea on the example of one-loop bubble and one-loop box integrals.
We see that the IBP relations form a left ideal in a rational double-shift algebra.
The IBP reduction of loop integrals then amounts to computing normal forms of shift operators of the rational double-shift algebra
with respect to a Groebner basis of the left ideal.
Finally, in the last part we discuss an ansatz based on linear algebra to simulate the computation of normal forms.
This approach can be used for complicated problems, when obtaining the Groebner basis is computationally too expensive. |
| Date: | Tue, 20.06.2023 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | Fakultaet fuer Physik, Erwin Schroedinger-HS, Boltzmanngasse 5, 5. Stock |
| Contact: | A. Hoang, M. Procura |
| The conformally invariant wave equation near the cylinder at spacelike infinity on a Schwarzschild background |
| Speaker: | Joerg Hennig (TU Clausthal) |
| Abstract: | We study the scalar, conformally invariant wave equation on a Schwarzschild background, which can be considered as a toy model for the conformal field equations for spacetimes with black holes. Even though the wave equation is a much simpler equation,it already mirrors important mathematical properties and difficulties of the general problem. Our main interest is in a suitable treatment of spatial infinity, which is represented as a cylinder. Firstly we consider the Cauchy problem for the wave equation. We study a family of equations intrinsic to the cylinder, where the solutions turn out to have, in general,logarithmic singularities at infinitely many expansion orders.
We derive regularity conditions that may be imposed on the initial data, in order to avoid the first singular terms. We then demonstrate that a fully pseudospectral time evolution scheme can be applied to solve the ... |
| Date: | Thu, 22.06.2023 |
| Time: | 10:00 |
| Duration: | 60 min |
| Location: | via ZOOM Meeting ID: 654 003 6841 Passcode: Gs4brS https://univienna.zoom.us/j/6540036841?pwd=SytyVkZJZzNyRG9lMm13ejlHeHRRUT09 |
| Contact: | P. Chrusciel, D. Fajman |
| Horizons are Watching You |
| Speaker: | Daine Danielson (University of Chicago) |
| Abstract: | We show that if a massive (or charged) body is put in a quantum superposition of spatially separated states in the vicinity of a black hole or cosmological horizon, the mere presence of the horizon will eventually decohere the superposition. In effect, the long-range fields sourced by the superposition register on the horizon, forcing emission of entangling âsoft gravitons/photonsâ through the horizon. In this way the horizon harvests âwhich pathâ information about the superposition. We estimate the decoherence time for such quantum superpositions in the presence of (Killing) horizons. Finally, we compute the quantum information content (viz. fidelity) of the superposed graviton/photon field in the black hole interior, relating the information accessible by any optimal observer(s) in the interior and the decoherence of the superposition in the exterior. (Based on arXiv:2301.00026, etc.) |
| Date: | Thu, 22.06.2023 |
| Time: | 15:00 |
| Duration: | 60 min |
| Location: | TU Wien, Freihaus, Seminar room 10th floor |
| Contact: | Romain Ruzziconi, Iva Lovrekovic |
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