
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 spinpolarized scanning tunneling microscopy (STM) experiments allow the determination of complex (noncollinear) surface magnetic structures in real space, like spinspirals, 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 3DWKB 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 810 
Contact:  Ao.Univ.Prof. Dr. Josef Redinger 
The Higgs boson as Inflaton 
Speaker:  Prof. Fred Jegerlehner (HumboldtUniversität 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 nonvanishing 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, ErwinSchrödingerHörsaal, Boltzmanngasse 5, 5. Stock 
Contact:  A. Hoang, H. Neufeld 
Towards Quantum Simulation with magnetic lattices 
Speaker:  Arthur La Rooij (van der WaalsZeeman Institute  University of Amsterdam) 
Abstract:  We use nanolithography 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 ebeam 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 Nonrelativistic String 
Speaker:  Charles MelbyThompson (Tokyo U., IPMU) 
Date:  Wed, 06.05.2015 
Time:  16:00 
Duration:  60 min 
Location:  SEM 136, TU Wien, Freihaus, 10th floor (Wiedner Hauptstr. 810, A1040 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 rightinvariant 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 volumepreserving 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 nonnegative 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 nonnegative 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. 810, A1040 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 HopfGalois 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. 810, A1040 Vienna) 
Contact:  Daniel Grumiller and Johanna Knapp 
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. 810, A1040 Vienna) 
Contact:  Daniel Grumiller and Johanna Knapp 
