CPT

Calendar of Physics Talks Vienna

Infinite derivative gravity in 2+1 spacetime dimensions
Speaker:Georg Stettinger (Univ. of Groningen, NL)
Abstract:I we will consider the most general quadratic curvature action of massless gravity in 3 space time dimensions which is parity invariant, torsion free and contains the same off-shell degrees of freedom as the Einstein-Hilbert action in general relativity. In the ultraviolet, with an appropriate choice of the propagator given by the exponential of an entire function, the point-like curvature singularity can be smoothened by a Gaussian distribution, while in the infrared the theory reduces to that of the predictions of general relativity. I will also show how to embed new massive gravity in ghost free infinite derivative gravity in Minkowski background as one of the infrared limits. Finally, I will provide the perturbative unitarity conditions for infinite derivative gravity in presence of a cosmological constant in deSitter and Anti-deSitter space times in 3 spacetime dimensions.
Date: Tue, 08.01.2019
Time: 13:45
Duration: 60 min
Location:TU Wien, Getreidemarkt 9, Maschinenbaugebäude, 1. Stock, HS Kleiner Schiffbau
Contact:S. Fredenhagen, D. Grumiller, J. Knapp

Renormalons, R-evoultion and Renormalon Sum Rule
Speaker:Christoph Regner (Univ. Wien)
Abstract:Perturbation series in QCD are generally known to be divergent and can at best be considered asymptotic.The asymptotic behaviour is caused by contributions from small and large loop momenta in perturbative calculations and manifests itself in poles of the corresponding Borel transform.These poles are usually referred to as renormalons and lead to ambiguities in the definition of perturbative series.In this talk we discuss the implications of these ambiguities and investigate how well renormalon ambiguities can be quantified.Furthermore it will be shown how the introduction of a new scale R can be used to improve the poor convergence behaviour of perturbative series suffering from renormalon ambiguities. From the solution of renormalization group equations with respect to the scale R (R-evolution),one can deduce an analytic all-order expression for the Borel transform of perturbative ....
Date: Tue, 08.01.2019
Time: 16:15
Duration: 60 min
Location:Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:A. Hoang, S. Plätzer, M. Procura

Emergence of non-Abelian magnetic monopoles and Anyonic statistics in quantum impurity problems
Speaker:Enderalp Yakaboylu (Institute of Science of Technology Austria)
Abstract:By virtue of emergent gauge fields in quantum impurity problems, we demonstrate that in experimentally realized regime the angulon, a quantum rotor dressed by bosonic excitations, can be seen as a point charge on a two-sphere interacting with a gauge field of a non-Abelian monopole. We find a topological transition associated with making the monopole Abelian, which takes place in the vicinity of the previously reported angulon instabilities. Furthermore, we show that identical impurities interacting with a two-dimensional many-particle environment obey anyonic statistics. In particular, we find that the bath manifests itself as an external magnetic flux tube with respect to the impurities, and hence the time-reversal symmetry is broken for the effective Hamiltonian describing the impurities. The emerging flux tube acts as a statistical gauge field after a certain critical coupling …
Date: Wed, 09.01.2019
Time: 14:15
Location:Seminar room FH gelb 10, Institute for Theoretical Physics – Vienna University of Technology, Wiedner Hauptstraße 8 – 10, 10th floor, B (yellow tower)
Contact:Joachim Burgdörfer

The waxing and waning of Alpine glaciers throughout the last 10,000 years
Speaker:Prof. Walter Kutschera (Vienna Environmental Research Accelerator (VERA), Faculty of Physics – Isotope Physics, University of Vienna)
Abstract:It is well known that the Holocene, i.e. the geological time period of the last 11,000 years following the end of the Ice Age, enjoyed relatively stable temperatures. But glaciers are sensitive to even small temperature and/or climate changes, and the globally observed retreat of Alpine glaciers and polar ice sheets since 1850 AD (the end of the so-called Little Ice Age) has been linked to the temperature rise caused by the ever increasing release of CO2 and other greenhouse gases by human activities. On the other hand, it is now evident that considerable glacial fluctuations occurred already at much earlier times when the human impact was negligible. In a way, the interest in Alpine glaciers of the past started with the accidental discovery of the famous Iceman Ötzi in 1991, a naturally mummified body which ... [full abstract available here: https://indico.smi.oeaw.ac.at/event/305/]
Date: Wed, 09.01.2019
Time: 17:00
Duration: 60 min
Location:Stefan-Meyer-Institut, Boltzmanngasse 3, 1090 Wien, Seminarraum 3-2-08 (2. Stock)
Contact:Prof. Dr. Eberhard Widmann, Dr. Martin Simon

De Donder-Weyl Hamiltonian theory and precanonical quantization: an untrodden path to quantization of fields and gravity
Speaker: Igor Kanatchikov (Univ. of St. Andrews, UK)
Abstract:I will discuss(I)the De Donder-Weyl (DW) Hamiltonian and Hamilton-Jacobi formulation of classical fields and the underlying mathematical structures which can be used for quantization (the polysymplectic structure and the Poisson-Gerstenhaber brackets),(II)a field quantization based on those structures (precanonical quantization) which leads to a hypercomplex rather than infinite-dimensional generalization of quantum theory as a description of quantum fields,(III)examples of precanonical quantization of a nonlinear scalar field on flat and curved background, and the pure Yang-Mills field, (IV) the consistency of precanonical quantization with the Ehrenfest theorem,(V)the relation to the standard QFT in the functional Schrödinger representation, which appears as a singular limiting case,(VI)precanonical quantization of general relativity in vielbein Palatini formulation and the .....
Date: Thu, 10.01.2019
Time: 14:00
Duration: 60 min
Location:Arbeitsgruppe Gravitation, Währinger Strasse 17, Raum 218, 2. Stock, 1090 Wien
Contact:P.T. Chrusciel, D. Fajman

Open quantum dynamics induced by light scalar fields
Speaker:Christian Käding (U. Nottingham & TU Wien)
Abstract:Light scalar fields have been interesting subjects for modifications of the standard model or general relativity in recent years. For example, a commonly employed alteration of Einstein‘s theory of gravity is achieved by conformally coupling a scalar field to the metric tensor. Light conformally coupling scalar fields are expected to cause a gravity-like fifth force of Nature and some have successfully been constrained in quantum experiments like atom interferometry. In this context it is important to understand open quantum dynamical effects like decoherence which can be induced by the presence of scalar fluctuations. I will illustrate how a robust and practicable formalism based on the influence functional can be used to derive a single particle momentum subspace master equation which describes the open quantum dynamics induced by conformally coupled scalar fields.
Date: Thu, 10.01.2019
Time: 16:00
Location:Institute for Theoretical Physics, TU Wien, Seminar room 10th floor (yellow area), Wiedner Haupstr. 8-10, 1040
Contact:Anton Rebhan