Vienna Theory Lunch Seminarby Iva Lovrekovic (VUT), Jakob Salzer (VUT), Tuesdays 12:1513:30
held alternately at:
We thank our kind sponsors: 
Idee: 
Wie auf vielen Universitäten praktiziert wollen wir ein LunchSeminar etablieren, das aktuelle Themen der Theoretischen Physik, die von DiplomandInnen, DoktorandInnen und PostDocs behandelt werden, aufgreift.

We want to establish a lunch seminar as practiced at other universities. The focus is on recent theoretical research done by Master students, PhDs and PostDocs.

Wie kann ich teilnehmen? 
Einfach erscheinen! Um per Email informiert zu werden, bitte in die Mailingliste eintragen. 
Just attend! To receive informations via email register for the Mailinglist. 
Oct 7 2014 
Stefan Prohazka 
Higher spins and Lifshitz holography with isotropic scale invariance Abstract: I will give an overview on higher spin theories in three and four dimensions and present interesting open questions. Furthermore I will answer the question if it is possible for an anisotropic Lifshitz critical point to exhibit isotropic conformal invariance by showing a concrete holographic realization. 
Oct 14 2014 
Bahman Dehnadi 
Charm and Bottom mass determinations from relativistic QCD sum rules at four loops Abstract: In this talk I will present our recent results on charm and bottom mass determinations based on perturbative QCD with a thorough analysis of theoretical uncertainties. 
Oct 21 2014 
Christian Ecker 
Numerical Holography Abstract: In recent years numerical holography (numerical relativity + AdS/CFT) has developed to a powerful tool for studying the dynamics of strongly coupled systems. I will review applications of this method to the nonequilibrium dynamics of heavy ion collisions and to the computation of entanglement entropy. 
Oct 28 2014 
Magdalena Zych 
Gravitational time dilation in quantum mechanics — for feasible tests of the quantumandgravity interplay Abstract: Quantum mechanics and general relativity have been extensively confirmed in many experiments but still all tests of the influence of gravity on quantum systems remain fully consistent with the nonrelativistic, Newtonian gravity. Rapidly developing quantum technologies allow for quantum experiments with increasingly complex systems. The regime where general relativity affects internal dynamics of such systems is just becoming available for experimental exploration and is likely to allow for first feasible tests of the interplay between quantum mechanics and general relativity. This talk will give an overview of new physical effects in this regime, in particular, resulting from the time dilation. These include new effects in interference of composite quantum systems and a universal decoherence mechanism affecting center of mass of all composite systems (with an internal energy spread). Moreover, in order to verify whether the phenomenon of gravity is indeed tantamount to space time geometry, in this regime novel experiments are necessary. For a geometric picture of gravity to hold, there must be a strict equivalence between the rest massenergy of the system, the massenergy that constitutes its inertia, and that constitutes its weight. In quantum mechanics internal energy of the system is given by a Hamiltonian operator and therefore this equivalence has to be satisfied by the entire rest, inertial and gravitational massenergy operators. In classical physics, the equivalence is only required between the massenergy values. Thus, validity of the geometric picture of gravity in classical physics does not guarantee its validity in quantum mechanics, which thus requires an independent verification. I will introduce an effective (lowenergy) testtheory, suitable to incorporate the above quantum formulation of the equivalence conditions, discuss new and sketch how it can be tested. 
Nov 4 2014 
Wout Merbis 
Massive Gravity and Holography in Three Dimensions Abstract: Modifications of General relativity (GR) have been a longstanding research problem. Motivated by cosmological observations, one specific modification of GR deals with assigning a small mass to the graviton, the force carrier of gravity. The resulting theory of massive gravity must be constructed in a careful way to avoid unphysical propagating degrees of freedom. Beside giving a general overview on this problem, the topic of this talk is to discuss the construction of a general class of three dimensional massive gravity models which steers clear of many pathologies found in previous models, in particular in relation to the holographic duality. 
Nov 11 2014 
Georg Wachter 
Ultrafast electron dynamics in condensed matter Abstract: Control of electron motion by external electric fields or voltages lies at the heart of modern electronics. While transistors operate on timescales in the picosecond regime, the fastest electronic processes in solids can be many orders of magnitude faster on the (sub)femtosecond time scale. In recent years, the ability of modern laser technology to customtailor strong timedependent optical electric fields has enabled unprecedented observation and control of electron motion in solids on the ultrafast time scale. Such strong field interaction with condensed matter promises lightfield electronics devices operating on the femtosecond time and nanometer length scale. Its theoretical exploration faces the challenge to simulate the timedependent manyelectron problem. We will briefly introduce the goals and building blocks of ultrafast physics. We then illustrate recent progress in the description of ultrafast electron dynamics in condensed matter with the help of two examples. Metal nanotips illuminated by fewcycle laser pulses become ultrafast electron emitters and the laser pulse steers the electron motion near the nanostructure. In large bandgap dielectrics such as quartz glass (SiO2), intense optical laser pulses can induce electron tunneling between neighboring atoms, leading to the efficient generation of quasifree carriers and a femtosecond transition from an insulator to a metal. Abinitio simulations based on timedependent density functional theory are found in good agreement to first experimental data and allow us to see and understand the electron motion on the atomic length and time scales. 
Nov 18 2014 
Peter Poier 
Effective Interactions for Colloids and Polymers in Soft Matter systems Abstract: In Soft Matter Physics we work with macromolecules like colloids or polymer chains. Instead of an atomistic description we often use a coarsegrained approach where the state of these large particles is described with an effective model that involves much less degrees of freedom. The main advantage of effective models is that they are computationally cheaper and in addition they facilitate an intuitive understanding of the Physics described. Another nice property of Soft Matter Systems is that the interactions in the effective model can be tuned easily by changing only the properties of the solvent (e.g. by adding salt). I will give some examples for interesting effective models in Soft Matter Physics. In particular I will introduce an effective model that leads to so called Cluster Crystals, which are a novel and interesting state of matter. I will explain how this effective model is related to a system of semiflexible ring polymers. In addition I will show recent results of simulations in which we monitor the localization probability of knots on polymer chains with heterogeneous rigidity under tension. 
Nov 25 2014 
Philip Schäffer 
How to get from the metric tensor to an EinsteinVlasov System in 45 minutes Abstract: A short introduction on some basic notions in GR like the metric tensor and topology of manifolds will be given. Furthermore an example for a cosmology will be given and its properties will be discussed. 
Dec 2 2014 
James Whitfield 
TDDFT: Vrepresentability on lattices Abstract: I will explain time dependent density functional theory and sketch our previous result concerning the computational complexity of solving the Vrepresentability problem. I will talk about some more recent results concerning a numerical implementation of our scheme. The talk will only require familiarity with linear algebra. 
Dec 9 2014 
Franz Kerschbaum 
Onboard intelligence for space telescopes Abstract: Space telescopes with their more and more complex instrumentation require specialized onboard IT systems. This is to cope with both highly specialized and demanding operational modes as well as the enormous volumes of data produced. Severe computational, power, mass and volume constraints together with limited communication rates and autonomous operation make such space IT systems and the respective onboard SW quite demanding and often mission critical. Over the last 1.5 decades the Department of Astrophysics at the University of Vienna built up extensive expertise in this very field of onboard data processing and more general onboard instrument software. Together with national and international partners past, current and future space missions are provided with our systems, e.g. Herschel, BriteConstellation, Cheops, Plato or Athena. Besides the technical aspects of our participations also a few astrophysical results and aims will be presented. 
Dec 16 2014 
Liang Si 
The ferromagnetic metal to nonmagnetic insulator phase transition in SrRuO3 ultrathin films Abstract: Using densityfunctional theory plus dynamic mean field theory (DFT+DMFT) method, we investigated the correlation effects in ultathin films of 4d transitionmetal oxide ferromagnetic metal SrRuO3. We found an intrinsic thickness limitation for preserving the ferromagnetism and metallicity: Single unit cell layer SrRuO3 becomes a robust insulator without ferromagnetism. Current experimental efforts such as strain and capping are hopeless towards the ferromagnetic ultrathin (singlelayer) SrRuO3; they could effectively tune the crystalfield splitting between Ru t2g orbitals, but drive a transition only between distinct paramagnetic and antiferromagnetic insulating states. 
Jan 13 2015 
Andreas Schmitt 
Neutron stars as a laboratory for fundamental physics Abstract: I will review general aspects and latest developments of how neutron stars can constrain properties of dense nuclear and quark matter. I will discuss theoretical challenges in dense QCD matter, but mainly focus on astrophysical signals and how they can be related to fundamental physics. 
Jan 20 2015 
Elena Ginina 
Lightest MSSM Higgs boson decay into a charm quarks pair at full one loop level with flavour violation Abstract: We study lightest neutral Higgs decay to a pair of charm quarks in the MSSM at full oneloop level with nonminimal quark flavour violation (QFV). In the numerical analysis we consider mixing between the second and the third squark generations and the relevant constraints from B meson data are taken into account. It is shown that the full oneloop corrected decay width can be quite sensitive to the MSSM QFV parameters due to large scharmstop mixing and large trilinear couplings. We summarise the theoretical and experimental errors and discuss the measurability of these SUSY QFV effects at the ILC. 
Jan 27 2015 
David Müller 
Superfluid density in a relativistic fermionic superfluid Abstract: In my talk I will discuss a fieldtheoretical model to describe a relativistic fermionic superfluid. Such superfluids are likely to be found in the cold dense matter inside neutron stars. I will talk about the meanfield approximation of the model and how to go beyond this approximation by introducing bosonic fluctuations. In particular I will show how to calculate the superfluid density in terms of Feynman diagrams. 
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