by Maximilian Attems & David Burke & Marcus Huber & Theodor Adaktylos

Di 12:30-13:30

abwechselnd auf der

TU Wien (E136, 10. Stock (gelb))

oder der

Uni Wien (Boltzmanngasse 5, 5.Stock, gr. Seminarraum (Schrödinger Hs )


Wie auf vielen Elite Unis praktiziert, wollen wir ein Lunch-Seminar 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 oder an marcus.huber et

Just attend! To receive infos per email got to Mailinglist or drop an email to mattems et oder an marcus.huber et


06. Oktober 2009

TU Wien

Gregor Kasieczka (HEPHY)

Re-Powering 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 re-discovery 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 signal-free. 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: two-dimensional massless Dirac Fermions

Graphene, a honeycomb-lattice 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 tight-binding simulation of realistic graphene quantum dots. In particular we study the influence of confinement and lattice defects on the electronic structure of graphene-based 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 (no-signaling) or impossibility of copying of unknown states (no-cloning). 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 non-classical 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 CP-odd effects in hot quark matter (pdf)

In hot quark matter, an imbalance in the number of right- and left-handed quarks will be induced by fluctuations of topological charge. This is a P- and CP-odd 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 CP-odd 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 quark-gluon plasma, a new state of matter at ultra-hot temperatures, for the time of a few yoctoseconds. Besides many particles that are produced in such collisions, also high-energy photons are emitted from the plasma. We focus on photons produced in the plasma through Compton scattering of gluons and quark-antiquark annihilation. Looking at the time-evolution 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 pump-probe experiments at nuclear time scales.

17. November 2009

TU Wien

Ching-Ming 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 D-branes have been studied recently. Gauge groups are from D-brane stacks and chiral fermions arise from strings stretching between D-branes intersecting at angles (Type IIA) and in its T-dual (Type IIB) picture with magnetized D-branes. Fluxes introduced in model building can stabilize the undetermined dilaton, complex, and Kaehler moduli in different vacua. So far several semi-realistic Pati-Salam and GUT models have been constructed in Minkowski and AdS vacua. A particular D-brane 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 four-point 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 mass-radius relationships of quark stars, as well as the breakdown of the Color-Flavor-Locked phase of color superconductivity.

1. Dezember 2009

TU Wien

Tomas Brauner (Frankfurt University)

Confinement and chiral symmetry breaking in QCD-like 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 QCD-like 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 model-independent 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 7-8, 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 V-A 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 pseudo-scalar 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 gravitational-wave (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 black-hole 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 black-hole 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