Vienna Theory Lunch Seminar

by Christian Ecker (VUT), Alexander Haber (VUT),
Moritz Preisser (UV) and Elke Aeikens (UV)

Tuesdays 12:15-13:30

held alternately at:

Vienna University of Technology (VUT): Wiedner Hauptstr. 8-10, yellow area, 10th floor, seminar room E136

University of Vienna (UV): Boltzmanngasse 5, 5th floor, Schrödinger Lecture Hall

We thank our kind sponsors:

Dean of physics, TU

Dean of physics, UV

Daniel Grumiller, TU



Wie auf vielen Universitäten praktiziert wollen wir ein Lunch-Seminar 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 Beginn des Masterstudiums dem Vortrag folgen kann. BachelorstudentInnen können besonders von dem Seminar profitieren, da es ihnen ermöglicht einen Eindruck in die Forschungsarbeit beider Universitäten zu erhalten. Die Vortragenden werden dabei auch ermutigt darüber zu sprechen, warum sie ein gewisses Forschungsgebiet gewählt haben. Dabei dürfen durchaus offene Fragen und Probleme behandelt werden und es ist nicht notwendig einen Vortrag über eine "perfekte", abgeschlossene Arbeit zu halten.

Damit es zu keinem "Zeitverlust" kommt, wird Mittagessen (Pizza) 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. Undergraduate 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).

Wie kann ich teilnehmen?

How can I join?

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 6 2015


No Lunch Seminar

Skipped due to the ÖAW workshop "100 years of curved space time".

Oct 13 2015


Maximilian Löschner
(University of Vienna)

Unitarisation of Anomalous Couplings in Vector Boson Scattering

Abstract: The Standard Model predicts the existence of quartic gauge boson couplings. The experimental test of their size has only begun recently. A model-independent approach to describe new physics effects in these couplings is the introduction of dimension-8 operators in an effective field theory framework. In this talk we will show that the unitarisation of the resulting anomalous couplings is a necessary condition when comparing theoretical predictions to experimental data. To this effect we have implemented the so called K-matrix unitarisation scheme in the parton-level Monte Carlo event generator VBFNLO and we present results obtained in this scheme. Moreover a new unitarisation method is proposed and a comparison between the K-matrix and other approaches for unitarisation like form factors is discussed.

Oct 20 2015


Michael Weber
(Stefan Meyer Institute)

Studying QCD matter with the ALICE detector

Abstract: According to QCD, strongly interacting matter at sufficient high energy density exists in a state of deconfined quarks and gluons, the so-called Quark Gluon Plasma (QGP). The ALICE detector at the LHC features the unique possibility to study QCD matter at high temperatures and small net-baryon densities. A complete set of observables measured in pp, p-Pb and Pb-Pb collisions allows to explore properties of the QGP, to study initial-state effects of heavy-ion collisions and to study particle production in the QCD vacuum. A selection of ALICE results from LHC Run-1 will be presented.

Oct 27 2015


Paul Klinger
(University of Vienna)

BKL Singularities

Abstract: The celebrated singularity theorems of Penrose and Hawking show that singularities are an essential feature of general relativity but give no information about their structure. In contrast the BKL conjecture, proposed by Belinski, Khalatnikov and Lifshitz in the 70s, gives a detailed model of generic singularities but is based on heuristic arguments and, while supported by simplified models and numerical simulations, has not yet been proven. Here I will present the Hamiltonian "Cosmological Billiard" formulation of the BKL model and describe a recent result using this framework.

Nov 3 2015


Colin Johnstone
(University of Vienna)

Pathways to Habitability: from disks, to active stars, planets and life

Abstract: The classical definition of planetary habitability states that for a planet to be able to have life, the surface temperature must be such that liquid water can exist on it's surface. Since the surface temperature of a planet is mostly, but not entirely, determined by it's distance from its star and the star's brightness, astrophysicists often talk about the 'habitable zone' in which a planet must be in order to be habitable. However, being in the habitable zone is not a gaurantee of habitability. Many other conditions must be satisfied in order for a planet to be habitable. In the Pathways to Habitability project, we study the formation of planets and planetary atmospheres from the initial circumstellar disk phase through the joint evolution of the star-planet system. In this talk, I will review our knowledge of some of the important physical mechanisms required for the formation of habitable planetary environments.

Nov 10 2015


Benjamin Rogers
(University of Vienna)

Quantum Effects in Biological Systems

Abstract: Certain biological processes, such as photosynthesis, photoreception and even the avian compass, appear to be surprisingly efficient or sensitive. Quantum explanations have been proposed, indicating that nature may take advantage of quantum coherence and entanglement to optimise these processes in a 'warm, wet and noisy' environment. This talk will give a broad picture of this intersection between quantum mechanics and biology, with a focus on the role of bipartite and multipartite entanglement in these systems.

Nov 17 2015


Behnoush Khavari
(IPM Teheran)

Holographic two-point functions in conformal gravity

Abstract: An application of the AdS/CFT conjecture, is the calculation of n-point correlation functions of a strongly coupled CFT which is dual to a specific gravity theory in AdS spacetime. This type of calculation is known as holographic renormalization. After a review on the subject of holographic renormalization within the theory of Einstein-Hilbert gravity in four dimensions, we turn to the case of 4d conformal gravity which is a higher derivative theory of gravity with the distinctive property of invariance under Weyl rescalings of the metric. We calculate 2-point functions of fields of the conformal field theory which is dual to the conformal gravity in AdS spacetime by means of holographic methods.

Nov 24 2015


Daniil Gelfand
(TU Vienna)

Modelling color dynamics for heavy-ion collisions

Abstract: In my talk I will give a short overview over the field of heavy-ion collisions with an emphasis on its initial stages. I will discuss how the initial conditions are described in the Color Glass Condensate framework and explain our efforts to simulate them using classical lattice gauge techniques and the Colored-Particle-In-Cell (CPIC) method.

Dec 1 2015


David Toneian
(TU Vienna)

Modeling hydrodynamic interactions in complex systems

Abstract: When studying systems where macroscopic objects are dissolved in a fluid, one may want to investigate phenomena where hydrodynamic interactions play an important role: the movement of particles induces a flow field, which in turn propagates and may influence far-away objects in interesting ways. In these cases, one can neither simply neglect the solvent, nor perform computer simulations on an atomistic scale since they are impracticably expensive, due to the orders of magnitude separating the characteristic length- and time-scales of the solvent and the solute. So-called "mesoscale" simulation techniques try to find a compromise, capturing the physically relevant aspects of the system while being computationally efficient. One such technique, called Multi-Particle Collision Dynamics, is described, and an extension is presented that allows one to simulate a viscoelastic (non-Newtonian) solvent. Some characteristic properties of such fluids are explored, from the points of view of both theory and simulation.

Dec 15 2015


Christian Rab
(University of Vienna)

Modelling of protoplanetary disks

Abstract: During the formation of low mass protostars, disks consisting of dust and gas are formed. These so called protoplanetary disks are the birthplaces of planets. After an introduction to star and disk formation, I will show a few examples of recent observational discoveries and briefly discuss some of the most interesting open questions in this field. The focus of my talk will be on modelling of protoplanetary disks by means of a radiation thermo-chemical disk model. This kind of model combines radiative transfer, heating/cooling processes and chemistry. The main goal of such a model is the direct comparison to observations to constrain the structure (e.g. density, temperature), the mass and the chemical composition of individual disks. Such information is crucial for the understanding of the planet formation process.

Jan 12 2016


Yu-Ming Wang
(University of Vienna)

Factorization, resummation and sum rules for heavy-to-light form factors

Abstract: I will review the theory status and recent progress in the precision calculations of heavy hadron decays, with an introduction to the fundamental questions in heavy quark physics and some general discussion on the experimental programs carried out in the flavor factories. Focusing on a personal selection of topics, this covers the determination of CKM matrix element |V_ub| from semileptonic B-meson decays and QCD aspects of electroweak penguin decays of Lambda_b baryons, putting an emphasis on the factorization proof of partonic Green functions with the aid of the method of regions and on the QCD resummation of parametrically large logarithms which can potentially lead to the breakdown of perturbative expansion in the strong coupling constant.

Jan 19 2016


Ayan Mukhopadhyay
(TU Vienna)

Explorations into new effective frameworks

Abstract: Effective quantum field theory is based on the philosophy that we can integrate out short distance physics and describe low energy phenomena using finite number of parameters. This is how we have been able to successfully describe many-body quantum phenomena so far. Nevertheless, for a variety of phenomena, including human psychology, quark-gluon plasma, etc. we require to integrate a huge range of length and time scales to be able to describe all aspects of the dynamics comprehensively. We will discuss how one can generalize the Wilsonian RG flow construction to integrate over short distance scales in a more efficient way in order to construct new effective frameworks for various phases and states of Quantum Chromodynamics, the fundamental theory of quarks and gluons. Our construction naturally leads to emergence of string theory dual descriptions of part of the degrees of freedom, as "shadow worlds" that play the role of giving a non-perturbative completion of usual perturbative descriptions of effective field theories.

Jan 26 2016


Daniel Samitz
(University of Vienna)



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