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Calendar of Physics Talks Vienna
| Where Time Begins: Causal Consequences of Signature Change |
| Speaker: | Nathalie RIEGER (Yale University) |
| Abstract: | The Hartle-Hawking "no-boundary" proposal redefines spacetime by offering a new way of thinking about the origin of the universe. Mathematically, this involves signature-type changing manifolds where a Riemannian region is smoothly joined to a Lorentzian region at the transition surface where time begins.
Motivated by the "no-boundary" proposal, I present a segment of a new framework for signature-changing manifolds, characterized by a degenerate yet smooth metric. Then I adapt some Lorentzian tools and results to the signature-type changing scenario, introducing new definitions that carry unforeseen causal implications. One such noteworthy consequence is the presence of time-reversing loops through each point on the locus of signature change. |
| Date: | Tue, 17.06.2025 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Erwin-Schroedinger Lecture Hall, 1090 Vienna, Boltzmanngasse 5, 5th floor |
| Contact: | S. Fredenhagen, M. Sperling |
| Inclusive semileptonic B decays: Current status and perspectives |
| Speaker: | Thomas MANNEL (University of Siegen) |
| Abstract: | Inclusive decays of hadrons with a single heavy quark can be described using the Heavy Quark Expansion (HQE).
After a brief introduction and motivation I will discuss the current status of the calculations used to extract the CKM matrix element Vcb and will give the perspectives to further increase the precision of the HQE. |
| Date: | Tue, 17.06.2025 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | Erwin-Schroedinger Lecture Hall, 1090 Vienna, Boltzmanngasse 5, 5th floor |
| Contact: | A. Hoang, H. Neufeld, J. Pradler, M. Procura |
| Time-periodic solutions to the 1D cubic wave equation |
| Speaker: | Filip FICEK (University of Vienna) |
| Abstract: | Time-periodic solutions to nonlinear dispersive equations have been the subject of many investigations over the years. The classic works prove the existence of small amplitude solutions with frequencies belonging to nowhere dense sets.
In this talk I will show numerical evidence suggesting existence of a completely new class of solutions for one-dimensional cubic wave equation on an interval with Dirichlet boundary conditions. Solutions belonging to it are characterised by large energies, have complicated mode compositions, and form intricate fractal-like patterns. Then I will show how these numerical results can be used to rigorously construct exact solutions belonging to this new class. Finally, I will demonstrate a systematic approach to analysing complex structures formed by these solutions. |
| Date: | Wed, 18.06.2025 |
| Time: | 14:15 |
| Duration: | 60 min |
| Location: | Seminarraum A, Waehringer StraÃe 17, 1090 Vienna, 2nd floor |
| Contact: | D. Fajman |
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