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Calendar of Physics Talks Vienna
| A proof of the constancy of surface gravity for non-degenerate compact horizons |
| Speaker: | Ettore Minguzzi (Firenze) |
| Abstract: | Smooth compact totally geodesic null hypersurfaces (horizons) arise naturally as Cauchy horizons for partial Cauchy hypersurfaces. Here I outline a recent proof that if they admit an incomplete generator (non-degenerate) then the surface gravity can be normalized to a non-zero constant. The proof is, in its most technical part, independent of the approach of Isenberg-Moncrief and Bustamante-Reiris. Also the result holds just under the dominant energy condition, i.e. no vacuum assumption is required. If time permits, I shall also outline the proof that they are actually Cauchy horizons bounded on one-side by a region of chronology violation. (This is joint work with Sebastian Gurriaran, ENS Paris-Saclay) |
| Date: | Thu, 28.10.2021 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | ZOOM https://univienna.zoom.us/j/6540036841?pwd=SytyVkZJZzNyRG9lMm13ejlHeHRRUT09 |
| Contact: | Piotr Chrusciel, David Fajman |
| Black-Hole Scattering, Eikonal Exponentiation and Gravitational Waves |
| Speaker: | Carlo Heissenberg (Nordita & Uppsala) |
| Abstract: | The eikonal exponentiation of gravity amplitudes is a non-perturbative resummation whereby certain high-energy divergent terms, which would naively violate unitarity bounds, combine into a harmless phase factor. Eikonal techniques also offer a natural strategy to calculate classical gravitational observables directly from the loop-expansion of scattering amplitudes. In this talk, I will discuss how the eikonal can be applied to obtain the deflection angle for the collision of two non-spinning black holes with generic center-of-mass energies, up to order O(G^3). This calculation captures both conservative and dissipative “radiation-reaction” effects, and yields a deflection angle with a smooth behavior at high energies, where it agrees with the universal massless result. [...] |
| Date: | Thu, 28.10.2021 |
| Time: | 16:30 |
| Duration: | 60 min |
| Location: | Seminar room, 10th floor, Yellow building |
| Contact: | Laura Donnay |
| Is the Chiral Magnetic Effect fast enough? |
| Speaker: | Karl Landsteiner (Univ. Autonoma Madrid) |
| Abstract: | It depends!
The Chiral Magnetic Effect (CME) is the generation of an electric current in a magnetic field due to a chirality imbalance. It is supposed to occur in non-central heavy ion collisions. We develop a holographic model to address the question how fast the CME builds up in an out-of-equilibrium setup.
Our findings indicate that there is a significant time delay. In the context of heavy ion collisions with a short lifetime of the magnetic field the model leads to the conclusion that the CME is not fast enough at the LHC but might well be observable at RHIC. Along the the way I will also try to briefly review the experimental efforts to measure CME and especially highlight the recent results from the isobar run at RHIC.
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| Date: | Fri, 29.10.2021 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Hybrid: TU Wien, conference room 9th floor (green), Wiedner Haupstr. 8-10 and https://tuwien.zoom.us/j/91735458787?pwd=cjBqK3ZCWHRZaFJXSS82dXFvWVNLZz09 |
| Contact: | Anton Rebhan (TU Wien) |
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