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Calendar of Physics Talks Vienna
| Topological defects and generalised orbifolds |
| Speaker: | Ingo Runkel (University of Hamburg) |
| Abstract: | Topological defects in quantum field theory can be understood
as a generalised notion of symmetry, where the operation is not required
to be invertible. Duality transformations are an important example of
this. By considering defects of various dimensions, one is naturally led
to more complicated algebraic structures than just groups. So-called
2-groups are a first instance, which arise from invertible defects of
codimension 1 and 2. Without invertibility one arrives at so-called
"fusion categories”. These structures are already visible in dimension
2, where the field theories are under much better control. I will focus
on two-dimensional conformal field theories and show how these higher
structures arise. I will explain how one can "gauge" such
non-invertible symmetries of 2d CFTs, that is, define a generalised
notion of an orbifold. Finally, time permitting, will briefly discuss
the |
| Date: | Tue, 16.11.2021 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Zoom: https://univienna.zoom.us/j/99228344965?pwd=czNhTjh2ZFNTbzRnN1Z3aG9CdnBmQT09 |
| Contact: | Romain Ruzziconi |
| New approach to (semi)inclusive DIS with QED and QCD factorization |
| Speaker: | Wally Melnitchouk (Jefferson Lab) |
| Abstract: | We present a new factorized approach to inclusive and semi-inclusive deep-inelastic scattering which treats QED and QCD radiationon equal footing,
and provides a systematically improvable approximation to the extraction of collinear and transverse momentum dependent parton distributions.
We demonstrate how the QED contributions can be well approximated by collinear factorization, and illustrate the application of the factorized approach
to QED radiation in inclusive scattering.For semi-inclusive processes, we show how radiation effects prevent a well-defined "photon-hadron" frame
and illustrate the utility of the new method by explicit application to the spin-dependent Sivers and Collins asymmetries.
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| Date: | Tue, 16.11.2021 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | ZOOM: https://univienna.zoom.us/j/93427906843?pwd=YjhSejdUVW16QjVQYUh5TVNSNFNhQT09 |
| Contact: | A. Hoang, M. Procura |
| Berry Phases and Wormholes |
| Speaker: | Moritz Dorband (University of Würzburg) |
| Abstract: | We consider Berry phases and entanglement for simple quantum mechanical models as well as for wormholes in gravity and their AdS/CFT interpretation. In both cases the Berry phases arise due to unitary transformations acting on subsystems of the considered models. In the quantum mechanical case where we use a simple model of two coupled spins, we act with a rotation on half of the system, while in the wormhole case, only one throat undergoes time evolution. Since both these transformations are unitary, the entanglement properties of the systems are not distinguishable by a local measurement. On the gravity side, we substantiate the results for the wormhole by an explicit calculation in two-dimensional gravity. We furthermore discuss how Berry phases are related to non-exact symplectic forms in parameter space. Again we consider simple quantum mechanical models and gravity wormholes. |
| Date: | Wed, 17.11.2021 |
| Time: | 13:00 |
| Duration: | 60 min |
| Location: | SEM 9th floor yellow tower, Freihaus, Wiedner Hauptstrasse 8-10, 1040 Vienna |
| Contact: | Daniel Grumiller |
| A Green's function proof of the positive mass theorem |
| Speaker: | Lorenzo Mazzieri (Trento) |
| Abstract: | In this talk we describe a new monotonicity formula holding along the level sets of the Green's function of an asymptotically flat 3-manifold
with nonnegative scalar curvature. Using such a formula, we obtain a simple proof of the celebrated positive mass theorem. In the same context,
and for 1 < p < 3, a Geroch-type calculation is performed along the level sets of p-harmonic functions, leading to a new proof of the Riemannian Penrose Inequality in some case studies.
The results are obtained in collaboration with V. Agostiniani and F. Oronzio. |
| Date: | Thu, 18.11.2021 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | ZOOM https://univienna.zoom.us/j/6540036841?pwd=SytyVkZJZzNyRG9lMm13ejlHeHRRUT09 |
| Contact: | Piotr Chrusciel, David Fajman |
| Symmetry Resolved Entanglement in AdS3/CFT2 |
| Speaker: | Suting Zhao (Würzburg) |
| Abstract: | For a QFT with U(1) global symmetry, a resolution of the reduced density matrix via the U(1) subregion-charge defined on the entangled region is allowed. This indicates the existence of a refinement of the usual entanglement entropy, which is the so-called "Symmetry-resolved entanglement entropy(SREE)". In this talk, I will discuss the symmetry-resolved entanglement in the context of AdS3/CFT2. I will start from a toy holographic model: Three-dimensional U(1) Chern-Simons Einstein gravity. The calculations of the SREE rely on the CFT charged moments. I will show that the holographic dual of the CFT charged moments can be simpily realized by inserting a U(1) Wilson line inside the bulk, with its holonomy being identified with the monodromy generated by the boundary vertex operators. The resulting U(1) SREE exhibits a universal equipartition behavior of the entanglement. [...] |
| Date: | Thu, 18.11.2021 |
| Time: | 16:30 |
| Duration: | 60 min |
| Location: | Seminar room 10th floor (yellow tower) |
| Contact: | Daniel Grumiller, Laura Donnay |
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