
Vienna Theory Lunch Seminar
by Frederic Brünner, Sebastian Frank, Philipp Köhler, Albert Georg Passegger and Stephan Stetina
Tuesdays 12:1513:30 held alternatively
at: TU Wien ( Wiedner Hauptstr. 810, yellow area,
10th floor, seminar
room E136 ) Uni Wien ( Boltzmanngasse 5, 5th floor, Schrödinger Lecture Hall / large seminar room ) We thank our kind
sponsors:

Idee: Idea: 
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. Das Niveau soll so gewählt
werden, dass jeder Student und jede Studentin am Ende des Studiums dem
Vortrag folgen kann. Die Vortragenden werden ermutigt keinen
"perfekten" Vortrag zu halten, und sollen hauptsächlich Ihre
Motivation, warum sie dieses Thema gewählt haben, wiedergeben. Dabei dürfen
durchaus offene Fragen und Probleme behandelt werden. Damit es zu keinem "Zeitverlust" kommt, wird Mittagessen (Pizza, Sushi) gratis zur Verfügung gestellt. 
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. The seminar
is designed for graduate students but should also be comprehensible to advanced undergraduate
students. Prediploma students are particularly encouraged to attend so that they receive
an overview of research activities conducted at both universities. Speakers are also encouraged to focus on their
motivation for choosing their particular topic and to present
open questions. In order to avoid any "loss of time" we provide a free lunch (pizza, sushi). 
Wie kann ich teilnehmen? How can I join? 
Einfach erscheinen! Um per Email informiert zu werden, bitte in die Mailinglist eintragen oder Mail an stetina at hep.itp.tuwien.ac.at oder an philipp.martin.koehler at univie.ac.at 
Just attend! To receive informations via email go to the Mailinglist or drop an email to stetina at hep.itp.tuwien.ac.at or philipp.martin.koehler at univie.ac.at 
Mar 5 2013 TU Wien 
S. Kumar Mallavarapu 
Superfluid and semisuperfluid strings Abstract: Recent literature mentions the formation of semisuperfluid strings in dense quark matter. The goal of the talk is to introduce these objects. The talk shall begin with a mention of fundamental ideas about strings. Relevant geometrical and topological ideas about gauge fields will also be discussed

Mar 12 2013 Uni Wien 
Bruno Mintz 
Phase diagram and surface tension in the threeflavor Polyakovquarkmeson model Abstract: We obtain the inmedium effective potential of the threeflavor PolyakovQuarkMeson model as a real function of real variables in the Polyakov loop variable, to allow for the study of all possible minima of the model. At finite quark chemical potential, the real and imaginary parts of the effective potential, in terms of the Polyakov loop variables, are made apparent, showing explicitly the fermion sign problem of the theory. The phase diagram and other equilibrium observables, obtained from the real part of the effective potential, are calculated in the meanfield approximation. The obtained results are compared to those found with the socalled saddlepoint approach. Our procedure also allows the calculation of the surface tension between the chirally broken and confined phase, and the chirally restored and deconfined phase. The values of surface tension we find for low temperatures are very close to the ones recently found for twoflavor chiral models. Some consequences of our results for the early Universe, for heavyion collisions, and for protoneutron stars are briefly discussed.

Mar 19 2013 TU Wien 
no lunch seminar 
no lunch seminar

Apr 9 2013 Uni Wien 
Jürgen Klepp 
Geometric Phase Properties in Neutron Optics Experiments Abstract: Special properties of mixedinput phases are investigated experimentally with polarized neutrons. In the first part, I will explain a measurement of spinor phases for mixed inputstates undergoing unitary evolutions. Phases of purely dynamical and purely geometric origin are measured as a function of the input purity of the neutron spinstate. Measuring suitable combinations of both, it has been demonstrated that the mixedstate geometric phase is not additive as it is the case for pure states. Nonadditivity is a natural consequence of the definition of the mixedstate phase as weighted average of the phase factors of all pure state components in the density matrix. In the second part, a test of the phase stability under noisy evolution is described.

Apr 16 2013 TU Wien 
Christoph Saulder 
TBA Abstract: One of the biggest mysteries in cosmology is Dark Energy, which is required to explain the accelerated expansion of the universe within the standard model. But maybe one can explain the observations without introducing new physics, by simply taking one step back and reexamining one of the basic concepts of cosmology, homogeneity. In standard cosmology, it is assumed that the universe is homogeneous, but this is not true at small scales (<200 Mpc). Since general relativity, which is the basis of modern cosmology, is a nonlinear theory, one can expect some backreactions in the case of an inhomogeneous matter distribution. Estimates of the magnitude of these backreactions (feedback) range from insignificant to being perfectly able to explain the accelerated expansion of the universe. In the end, the only way to be sure is to test predictions of inhomogeneous cosmological theories, such as timescape cosmology, against observational data. If these theories provide a valid description of the universe, one expects aside other effects, that there is a dependence of the Hubble parameter on the line of sight matter distribution. The redshift of a galaxy, which is located at a certain distance, is expected to be smaller if the environment in the line of sight is mainly high density (clusters), rather than mainly low density environment (voids). Here we present a test for this prediction using redshifts and fundamental plane distances of elliptical galaxies obtained from SDSS DR8 data. In order to get solid statistics, which can handle the uncertainties in the distance estimate and the natural scatter due to peculiar motions, one has to systematically study a very large number of galaxies. Therefore, the SDSS forms a perfect basis for testing timescape cosmology and similar theories. The preliminary results of this cosmological test and the necessary calibrations will be discussed in this talk.

Apr 23 2013 Uni Wien 
Mauricio Leston 
Recents developments in nonperturbative QFT in curved spacetimes Abstract: The socalled constructive QFT approach has provided several examples of interacting QFT for D=2 and D=3 Minkowski spacetime. That was done by the use of a well defined Euclidean functional integral. Some years ago, certain steps of this approach have been extended to D=2 static spacetimes. In this talk I will briefly review the Euclidean formulation of QFT in Minkowski space time, with special emphasis on the notion of reflection positivity and its importance in the constructive quantum field theory approach. Then, I will describe its recent extension to static spacetimes and some open problems.

Apr 30 2013 TU Wien 
No lunch seminar 
No lunch seminar due to ESI anniversary symposium For informations, visit esi.ac.at

May 7 2013 Uni Wien 
Maximilian Attems 
Kinetic models of ultrarelativistic heavy ion collisions Abstract: Ultrarelativistic heavy ion collision experiments probe strongly
interacting matter under extreme conditions. The theory of the strong
interaction quantum chromodynamics (QCD) predicts the creation of a
QuarkGluon Plasma (QGP) in such collisions. The theoretical description
of the QGP dynamical evolution requires a wide range of tools.
The initial condition of the nuclei before the collision as well
as the gluon dynamics right after the collision is governed by
YangMills dynamics. Soon after the collision the system reaches
local equilibrium and hydrodynamics describes the expansion.
As the system gets more dilute, hadronic kinetic theory models become
applicable. Progress on studies of the nonAbelian plasma instabilities
for early stage dynamics and first results from a new pion gas
implementation will be presented.

May 14 2013 TU Wien 
Gergely Endrödi 
QCD thermodynamics in external magnetic fields Abstract: The hadron resonance gas model and numerical lattice simulations are employed to
study the response of the QCD vacuum to external magnetic fields, both at zero
temperature and in the deconfinement/chiral transition region. The quark condensate
and the trace anomaly are found to undergo magnetic catalysis at low temperatures
and inverse catalysis around Tc, respectively. The magnetization is determined to be
positive, indicating a paramagnetic QCD vacuum.

May 28 2013 Uni Wien 
Gernot Eichmann 
Hadron physics in the DysonSchwinger approach Abstract: I will give a brief overview of DysonSchwinger, BetheSalpeter and Faddeev equations and their application to hadron physics. Recent progress on various nucleon and delta elastic and transition form factors, nucleon Compton scattering, and a tetraquark interpretation of the sigma meson will be discussed.

Jun 4 2013 TU Wien 
Hiromishi Nishimura 
Confining gauge theories on R3 X S1 with Higgs Abstract: I will review some aspects of confining gauge theories on R3 X S1.
YangMills theory with certain centerstabilizing potentials is in the
confined phase at small S1, and we can study confinement analytically
using the semiclassical methods. Extending the theories with adjoint
scalar fields, we show that there is a new type of confined phase and that
the topological objects in this phase generalize BPS and KK monopoles,
which are constituents of instantons. I will also argue how one may be
able to take the theory at large R3 X S1 by the Poisson resummation.

Jun 11 2013 Uni Wien 
Valentina Verduci 
PionNucleon scattering in Lattice QCD Abstract: We investigate the Swave pionnucleon scattering in lattice QCD, in order to obtain new information on the negative sector of the nucleon spectrum. This approach enables us to shed some light on the nucleon excited states and can be generalized to the study of other sectors of the QCD spectrum.

Jun 18 2013 TU Wien 
Paul Tiwald 
From single atoms to solids  Quantum chemistry in solid state physics Abstract: I will give an introduction to quantum chemistry methods and their
application to solid state and surface physics within the embedded
cluster approach. Two topics currently under investigation will be
presented. The first topic is the Fcenter in Lithium Fluoride (LiF), a
point defect giving rise to bound electronic states. The second topic is
the interaction dynamics and the charge transfer of a proton approaching
a LiF surface.

Jun 25 2013 Uni Wien 
Harold Steinacker 
From Matrices to Quantum Geometry Abstract: Based on simple examples of quantized spaces described in terms of matrices, we explore the idea that physical spacetime might be described in terms of similar quantum spaces and quantum geometry. The emphasis of this talk is to explain how geometry can arise from matrices, based on the analogy with quantum mechanics.

Program Winter Semester 2012/2013