ViennaTheoryLunchClubSeminar

Idee/Idea:  Wie auf vielen Elite Unis praktiziert, wollen wir ein LunchSeminar etablieren, das aktuelle Themen der Theoretischen Physik, die auf unseren Unis von DiplomandInnen, DoktorandInnen und Postdocs behandelt werden, aufgreifen. Das Niveau soll so sein, dass jeder Student und jede Studentin am Ende des Studiums dem Vortrag folgen kann! Die Vortragenden werden auch ermutigt, keinen "perfekten" Vortrag zu halten, sondern haupsächlich zu motivieren, warum sie dieses Thema gewählt haben, und dabei dürfen auch durchaus offene Fragen und Probleme behandelt werden. Damit es zu praktisch keinen "Zeitverlust" kommt, wird gratis ein Mittagessen (Pizza,...) zur Verfügung gestellt. 
We want to establish a Graduate Student Lunch Club as praticed at other institutions like MIT. The seminars are designed for graduate students and should be accesible to all students. Students before their Diploma are particularly encouraged to attend so that they may learn about research begin performed on both universities. Speakers are encouraged to focus also on their motivation why they chose this particular topic and raise open questions. In order to avoid any "loss of time" we provide a free lunch (pizza,...). 
Wie kann ich teilnehmen?/ How can I join? 
Einfach erscheinen! Falls man per Email informiert werden möchte, besuche die Seite Mailinglist oder Mail an mattems et hep.itp.tuwien.ac.at oder an marcus.huber et univie.ac.at 
Just attend! To receive infos per email got to Mailinglist or drop an email to mattems et hep.itp.tuwien.ac.at oder an marcus.huber et univie.ac.at 
06. Oktober 2009 TU Wien 
Gregor Kasieczka (HEPHY) 
RePowering the LHC: What to expect from the first months, how we search for SUSY and my involvement(pdf)
After the incident in September 2008, considerable effort went into
the repair of the affected sectors, quality assurance for all parts
and the design of additional security measures. Confidence is high
that starting from November the accelerator will be up and running and
data be taken.
The talk will be split into three parts: First a glance at the planned
work in the first weeks and months after powering on the LHC will be
given. The main goal in this period will be the rediscovery of the
standard model.
A possible early discovery at the LHC is Supersymmetry. The second
part will summarize the efforts of the CMS collaboration in that
direction.
Finally I would like to present one of the central aspects in the work
of the CMS Analysis Group at HEPHY  Data Driven Background
estimation. For early data, the computer simulated predictions for the
background of the expected supersymmetric events are subject to high
uncertainities. It is desirable to employ strategies that estimate the
background in the signal region by using information from regions that
are expected to be signalfree. Such methods will be discussed and the
discriminating power for the first months of data taking examined.

13. Oktober 2009 Uni Wien 
Lukas Geyrhofer (Uni Wien) 
Phasetransitions in network dynamics (pdf)
Boolean networks are dynamical systems, consisting of N interacting
units, whose states are described by Ising spin variables. They are discrete
in time and each node is randomly connected to several others. Such
networks have been used to model e.g. gene regulatory networks in cells,
neural networks in brain function or social networks in simulating decision
making processes. Due to the randomness inherited by the model we
can use a mean field theory, where the time evolution of macroscopic
variables can be derived analytically. Dynamical phasetransitions can
be characterized by change in stability, existence and number of fixed
points in the magnetization and Hamming distance, which are the two
main macroscopic parameters in describing the dynamics. In particular,
the mean field method can be applied to Linear Threshold Functions, a
specific subclass of all possible functions in the network, where crucial
results for the critical parameters for phase transitions can be obtained.

20. Oktober 2009 TU Wien 
Florian Libisch (TU Wien) 
Graphene: twodimensional massless Dirac Fermions
Graphene, a honeycomblattice of carbon atoms, has attracted
considerable attention since its first experimental realization in
2004. In particular, the linear dispersion relation near the
Fermi energy connects the dynamics of electrons in graphene
to the ultrarelativistic Dirac equation. We discuss the implications
and limitations of this analogy: we compare predictions based
on the Dirac picture (e.g. Klein tunneling or suppressed backscattering)
to a tightbinding simulation of realistic graphene quantum dots. In
particular
we study the influence of confinement and lattice defects on the electronic
structure of graphenebased nanodevices. We find that the Dirac
properties of graphene are very sensitive to breaking of the sublattice
symmetry,
in particular at the edges of the sample. Experimental realizations of
Dirac physics in graphene nanoelectronics will thus depends on a smooth edge
confinement.

27. Oktober 2009 Uni Wien 
Borivoje Dakic (Uni Wien) 
Reconstruction of Quantum Theory: Bits, Locality, Continuity
Quantum theory makes the most accurate empirical predictions and yet it
lacks simple, more easily comprehensible
physical principles from which the theory can be derived uniquely. A
broad class of probabilistic
theories exist which all share features with quantum theory, such as
probabilistic predictions for individual
outcomes (indeterminism), impossibility of information transfer faster
than the light velocity (nosignaling) or
impossibility of copying of unknown states (nocloning). A vast majority
of attempts to find physical principles
behind quantum theory fall short of singling out quantum theory uniquely
or are based on abstract mathematical
assumptions that call themselves for a more compelling physical
motivation. Here, we reconstruct quantum theory from three reasonable
axioms:
(1) (Information capacity) All systems of information carrying capacity
of one bit have the same properties,
(2) (Locality) The state of a composite system is completely determined
by measurements on subsystems,
(3) (Continuity) Between any two pure states (i.e. states for which
there is a measurement with a definite outcome)
there exists a continuous reversible transformation. We show that
probability theories different than quantum theory cannot exhibit
entanglement and thus
nonclassical correlations that violate local realism unless that are in
conflict with one or more axioms.

03. November 2009 TU Wien 
Harmen Warringa (Frankfurt University) 
P and CPodd effects in hot quark matter (pdf)
In hot quark matter, an imbalance in the number of right and
lefthanded quarks will be induced by fluctuations of topological
charge. This is a P and CPodd effect, and can potentially be
relevant during heavy ion collisions. The question then is how one
could investigate this imbalance in experiment. In this talk I will
show that enormous magnetic fields are created in heavy ion collisions
in the direction of angular momentum of the collision. I will explain
that such imbalance naturally leads to generation of an electric
current in the direction of the magnetic field. The magnitude of this
current can be computed quantitatively. In heavy ion collisions, this
current leads to separation of charge which in principle can be
addressed experimentally by measuring specific charge correlations. As
such these correlations could be a probe for P and CPodd effects in
QCD. I will discuss exciting results from the STAR collaboration on
such charge correlations.

10. November 2009 Uni Wien 
Andreas Ipp (TU Wien) 
Yoctosecond light flashes from heavy ion collisions (pdf)
Collisions of heavy ions in particle accelerators like RHIC and soon LHC
can produce the quarkgluon plasma, a new state of matter at ultrahot
temperatures, for the time of a few yoctoseconds. Besides many particles
that are produced in such collisions, also highenergy photons are emitted
from the plasma. We focus on photons produced in the plasma through
Compton scattering of gluons and quarkantiquark annihilation.
Looking at the timeevolution of the photon emission for the
anisotropically expanding plasma, we find under certain conditions
double pulses at the yoctosecond time scale. Such double pulses may
be utilized in the future for novel pumpprobe experiments at
nuclear time scales.

17. November 2009 TU Wien 
ChingMing Chen (TU Wien) 
Type II String Vacua and Phenomenology (pdf)
The goal of string phenomenology is to find a convincing connection
between realistic particle physics and string theory. Type II
compactifications involving Dbranes have been studied recently.
Gauge groups are from Dbrane stacks and chiral fermions arise from
strings stretching between Dbranes intersecting at angles (Type IIA)
and in its Tdual (Type IIB) picture with magnetized Dbranes. Fluxes
introduced in model building can stabilize the undetermined dilaton,
complex, and Kaehler moduli in different vacua. So far several
semirealistic PatiSalam and GUT models have been constructed in
Minkowski and AdS vacua. A particular Dbrane model is chosen to
explore its phenomenology. It is also possible to generically study
the soft supersymmetry breaking terms, from which can be calculated
the supersymmetric partner spectra from supergravity parameters.
Fermion masses and mixings can be controlled by the three and
fourpoint functions using Yukawa couplings which arise from the
string worldsheet instantons.

24. November 2009 Uni Wien 
Aleksi Vuorinen (Bielefeld University) 
Cold quark matter (pdf)
I will discuss various properties of cold but dense QCD matter,
concentrating on our current knowledge on the phase structure of the
theory, the physical systems where these conditions may be realized, as
well as the computational tools we have available to describe the system.
In particular, I will present results from a recent calculation of the QCD
equation of state at zero temperature and finite quark number density,
including two light and one massive quark flavor. These results can be
used to address questions such as the existence of stable strange quark
matter, the massradius relationships of quark stars, as well as the
breakdown of the ColorFlavorLocked phase of color superconductivity.

1. Dezember 2009 TU Wien 
Tomas Brauner (Frankfurt University) 
Confinement and chiral symmetry breaking in QCDlike theories (pdf)
One of the outstanding issues concerning the physics of
strong
interactions is the interplay of confinement and chiral symmetry
breaking
and the location of the respective phase transitions in the QCD phase
diagram. While they are known to coincide at zero chemical potential,
different scenarios exist for the region of nonzero baryon density.
Direct
lattice simulation is not feasible due to the sign problem. However,
there
are certain QCDlike theories which do not suffer from the sign
problem.
Two such representatives are QCD with two colors and QCD with adjoint
quarks. I will discuss modelindependent expectations for their phase
diagrams as well as predictions from model calculations. I will argue
that available lattice data for these theories may provide us with the
necessary insight to understand the physics of deconfinement in cold
dense matter.

Friday 11. December 2009 Uni Wien 
Wolfgang Waltenberger (HEPHY) 
Musings on the LHC (pdf)
During the weekend of November 78, 2009, CMS saw the first
signal this year from 450 GeV protons that were dumped into a
collimator, right after they had passed through three octants of the
LHC accelerator. I take this opportunity to briefly review the history
of the
LHC from a user's perspective. The current status of the machine is
then presented.
Finally, I will present new techniques for the search for physics
beyond the
Standard Model.

15. Dezember 2009 TU Wien 
Mario Pitschmann (TU Wien) 
Recent Results on the Beta Decay of the Neutron (pdf)
Results obtained recently and expected in the nearest future of high
precision measurements of correlation coefficients and lifetime of the
neutron beta decay pose a crucial test for the Standard Model of
elementary particle physics. Currently, standard VA theory allows to
obtain the measured neutron lifetime within one standard deviation.
Using the expectation values of the necessary Standard Model
parameters a discrepancy of 0.8 seconds appears between theoretical
and experimental values. In order to obtain such results theoretically
one has to take into account radiative corrections to electroweak
interactions, contributions of the weak magnetism, proton recoil
energy etc. In the next three years new experiments are planned, which
should allow to find contributions of new physics related to scalar,
tensor and pseudoscalar extension of the Standard Model and possibly
of supersymmetry.

12. Januar 2010 Uni Wien 
Daniel Nagaj (RCQI Bratislava) 
Local Hamiltonians finding ground states in quantum computation 
19. Januar 2010 TU Wien 
Mark Hannam (Uni Wien) 
Numerical relativity and the sound of two black holes colliding
Accurate theoretical predictions of the gravitationalwave (GW) signals
produced by the merger of two black holes may be crucial for the first
direct detection of GWs; they will certainly be necessary as the new
field of GW astronomy develops. The GWs predicted by Einstein's equations
for blackhole mergers can only be calculated by computer simulations. I
will review progress in this rapidly advancing field, and the problems
that must be solved before observations of blackhole mergers can become
standard tools in experimental astrophysics, cosmology
and fundamental physics.

26. Januar 2010 Uni Wien 
Wolfgang Frisch (HEPHY) 
Loop Calculations in MSSM 
Programme Summer Semster 2009
Programme Winter Semster 2008/2009