CPT

Calendar of Physics Talks Vienna

Complex magnetic structures at surfaces and their imaging with STM from first principles
Speaker:Krisztián Palotás (Budapest University of Technology and Economics, Department of Theoretical Physics, Budapest/Hungary)
Abstract:During Recent advances in spin-polarized scanning tunneling microscopy (STM) experiments allow the determination of complex (non-collinear) surface magnetic structures in real space, like spin-spirals, skyrmions. Motivated by these advancements, there is a strong need for theoretical understanding of the observed magnetic structures. In the first part of the talk I present recent theoretical results on a diversity of complex magnetic structures in thin magnetic films at surfaces obtained by a combination of ab initio and spin dynamics calculations. Understanding STM image contrast is of crucial importance in surface science and related technologies. In the second part of the talk I present different tip effects on the STM contrast for a number of technologically relevant surfaces resulting from a combination of first principles calculations and 3D-WKB tunneling theory. Examples include a
Date: Tue, 05.05.2015
Time: 16:00
Location:Technische Universität Wien, Institut für Angewandte Physik, E134 yellow tower „B“, 5th floor, Seminarraum 134A (room number DB05L03) 1040 Wien, Wiedner Hauptstraße 8-10
Contact:Ao.Univ.Prof. Dr. Josef Redinger

The Higgs boson as Inflaton
Speaker:Prof. Fred Jegerlehner (Humboldt-Universität zu Berlin)
Abstract:The Higgs has been discovered to have a very peculiar mass value, which, depending on some technical details in calculating MSbar parameters in terms of physical ones, allows the Standard Model to work up to the Planckscale. This requires the Higgs potential to remain stable. If so, it turns out that the bare Higgs mass square changes sign at some value below the Planck scale. Assuming that the SM is a low energy effective theory ofsome cutoff system residing at the Planck scale, the bare parameters arethe ones relevant at very high energies as they existed in the early universe after the Big Bang. The change of sign of the bare Higgs mass square triggers the Higgs mechanism. The broken phase characterized by a non-vanishing Higgs vacuum expectation value is realized below the Higgstransition temperature, while in the very early universe the SM is in the symmetric phase, .....
Date: Tue, 05.05.2015
Time: 16:15
Duration: 60 min
Location:Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:A. Hoang, H. Neufeld

Towards Quantum Simulation with magnetic lattices
Speaker:Arthur La Rooij (van der Waals-Zeeman Institute - University of Amsterdam)
Abstract:We use nano-lithography techniques to create lattice potentials in permanent magnetic films at atom chips. These lattices can be created over a large range of length scales and are used to trap mesoscopic clouds of ultracold atoms. In our current experiments we use a 10 micron lattice spacing to study Rydberg physics with clouds up to 400 atoms. In parallel, we are downscaling the lattice spacing for a new series of experiments. On these new atom chips we created lattices with lattice spacing varying from 250nm up to 5um on the same chip. I will discuss but the current experiments and the fabrication of these new magnetic potentials. These chips were then patterned by e-beam lithography and etched with an Ar plasma to obtain structures with a 20nm resolution. This technique can extend the range of length scales of optical lattices to both smaller and larger sizes, and can be used to study degenerate gases in new regimes and environments. Also geometrical interfaces have been constructed to study the role of disorder, frustration and dimensionality for atoms on a lattice. Recently we developed new magnetic Rectangular, Kagome and Hexagonal potentials that we will use in our quantum simulation experiments.
Date: Wed, 06.05.2015
Time: 14:00
Location:Atominstitut, Seminarraum, Stadionallee 2, Wien 2
Contact:J. Schmiedmayer

Double Field Theory and the Non-relativistic String
Speaker:Charles Melby-Thompson (Tokyo U., IPMU)
Date: Wed, 06.05.2015
Time: 16:00
Duration: 60 min
Location:SEM 136, TU Wien, Freihaus, 10th floor (Wiedner Hauptstr. 8-10, A-1040 Vienna)
Contact:Daniel Grumiller and Johanna Knapp

Riemannian geometry of the diffeomorphism group
Speaker:Martin Bruveris (Brunel University London)
Abstract:Seminars in Geometric Analysis and Physics (GAP Seminar): This talk will survey the relationship between right-invariant Riemannian metrics on the diffeomorphism group and PDEs. We will concentrate in particular on Euler's equations for incompressible fluids, which correspond to geodesics on the volume-preserving diffeomorphism group. Afterwards we will concentrate on some mathematical result about the Riemannian geometry of diffeomorphism groups with Sobolev metrics, in particular completeness results.
Date: Thu, 07.05.2015
Time: 11:00
Duration: 60 min
Location:Arbeitsgruppe Gravitation, Währinger Strasse 17, Seminarraum Kernphysik, 5. Stock, 1090 Wien
Contact:M. Bauer (Fak. Math, U.V.), V. Branding (Fak. Math, T.U.), D. Fajman (Fak. Phys, U.V.), J. Joudioux (Fak. Phys, U.V.)

Minimal surfaces, isoperimetry, and non-negative scalar curvature in asymptotically flat manifolds
Speaker:Michael Eichmair (Vienna)
Abstract:im Rahmen des Literaturseminars: It is a classical observation that geodesic balls at points of positive scalar curvature contain more volume than a round ball in Euclidean space with the same surface area. In this talk, I will discuss the global effect of non-negative scalar curvature on isoperimetry in asymptotically flat manifolds.
Date: Thu, 07.05.2015
Time: 14:00
Duration: 60 min
Location:Arbeitsgruppe Gravitation, Währinger Strasse 17, Seminarraum A, 2. Stock, 1090 Wien
Contact:P.T. Chrusciel

BMS symmetries in three dimensions
Speaker:Blagojevic Oblak (Brussels U.)
Date: Thu, 07.05.2015
Time: 14:15
Duration: 60 min
Location:SEM 136, TU Wien, Freihaus, 10th floor (Wiedner Hauptstr. 8-10, A-1040 Vienna)
Contact:Daniel Grumiller and Johanna Knapp

BiGalois objects and the Brauer Picard group
Speaker:Simon Lentner (Uni Hamburg)
Abstract:I will explain the notion of a Hopf-Galois and -BiGalois object, which can be used to describe monoidal autoequivalences of representations categories of Hopf algebras. As an example I will show some curious occurrences in the category of representations of a finite group. Then I will talk about my recent work on trying to determine the group of braided autoequivalences for the Drinfel'd double of a finite group and hence the Brauer Picard group. This work should have applications in Dijkgraaf Witten type Topological Field Theories.
Date: Thu, 07.05.2015
Time: 14:15
Duration: 60 min
Location:ESI (kleiner Hörsaal)
Contact:Nils Carqueville

Holographic Superconductors in Helical Backgrounds and Homes' Law
Speaker:Rene Meyer (Tokyo U., IPMU)
Date: Thu, 07.05.2015
Time: 16:15
Duration: 60 min
Location:SEM 136, TU Wien, Freihaus, 10th floor (Wiedner Hauptstr. 8-10, A-1040 Vienna)
Contact:Daniel Grumiller and Johanna Knapp

Non-relativistic Gravity
Speaker:Eric Bergshoeff (Groningen U.)
Date: Fri, 08.05.2015
Time: 10:00
Duration: 60 min
Location:SEM, TU Wien, Freihaus, yellow tower, 3rd floor (Wiedner Hauptstr. 8-10, A-1040 Vienna)
Contact:Daniel Grumiller and Johanna Knapp