Calendar of Physics Talks Vienna

Vienna Physics Colloquium
Speaker:Pablo Debenedetti (VPC)
Abstract:Title: Computational Investigation of the Liquid-Liquid Transition in Deeply Supercooled Water
Date: Mon, 11.12.2017
Time: 17:00
Location:Lise Meitner Lecture Hall, Strudlhofgasse 4 first floor, 1090 Wien

Soft hairy warped black hole entropy
Speaker:Philip Hacker (TU Wien)
Abstract:We reconsider warped black hole solutions in topologically massive gravity and find novel boundary conditions that allow for soft hairy excitations on the horizon. To compute the associated symmetry algebra we develop a general framework to compute asymptotic symmetries in any Chern--Simons-like theory of gravity. We use this to show that the near horizon symmetry algebra consists of two u(1) current algebras and recover the surprisingly simple entropy formula S=2π(J_0^+ + J_0^-), where J_0^± are zero mode charges of the current algebras. This provides the first example of a locally non-maximally symmetric configuration exhibiting this entropy law and thus non-trivial evidence for its universality.
Date: Tue, 12.12.2017
Time: 14:00
Duration: 60 min
Location:Schrodinger lecture hall (5th floor), University Vienna, Strudlhofgasse 4/Boltzmanngasse 5
Contact:Daniel Grumiller and Stefan Fredenhagen

A Transmission Source System for PET Attenuation Correction in PET/MR Imaging
Speaker:Andreas Renner (TU Wien, IAP and Center for Medical Physics and Biomedical Engineering, Medical University of Vienna)
Abstract:The combination of Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) systems provides additional benefit for diagnostic imaging. Accurate attenuation correction (AC) is a challenge in PET/MRI compared to stand-alone PET and PET/CT. In the absence of photon transmission sources in PET/MRI, methods for AC rely in general on the retrospective segmentation of MR images or complex additional MR sequences. Most methods neglect attenuation of bone to a significant extent. We have therefore developed a fully integrated transmission system for PET/MRI to enable direct measurement of attenuation using external gamma emitters, which is the gold-standard in AC. This presentation illustrates the basic physical principles of PET as well as AC and introduces our transmission system. Results achieved by this novel setup are presented and discussed.
Date: Tue, 12.12.2017
Time: 16:00
Location:Technische Universität Wien, Institut für Angewandte Physik, E134 yellow tower „B“, 5th floor, Sem.R. DB gelb 05 B (room number DB05L03), 1040 Wien, Wiedner Hauptstraße 8-10
Contact:Ao.Univ.Prof. Dr. M. Gröschl

Vector-Boson Fusion and Scattering
Speaker:Michael Rauch (KIT)
Abstract:Production of electroweak bosons via vector-boson fusion and scattering (VBF) is one of the main process classes to study at current and future runs of the LHC. Its double-DIS-like structure gives rise to the characteristic signature of two tagging jets in the forward regions of the detectors, and distinguishes it from QCD-induced processes, which exhibit much more central jet activity. In this talk, we discuss the main features of the VBF process class, investigate the effects of combining NLO QCD results with parton-shower effects using the latest versions of VBFNLO 3 and Herwig 7, and look at the first NNLO QCD calculation in this process class, performed for VBF-H production. VBF processes also allow to study the triple and, in particular, quartic gauge couplings and test them for new-physics effects. We show arising challenges like unitarity violation when . . . .
Date: Tue, 12.12.2017
Time: 16:15
Duration: 60 min
Location:Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:H. Neufeld, S. Plätzer

Primordial Black Hole Cosmology
Speaker:Prof. Kazunori Kohri (KEK)
Abstract:After LIGO detected gravitational wave events produced by mergers of binary black holes (BHs) in 2015, researchers have aggressively studied the origin of the BHs with masses of the order of O(10) M_solar. In additional to astrophysical origins such as evolution of Pop.II and/or Pop.III stars, one of the attractive candidates of those BHs would be Primordial Black Holes (PBHs) which were produced in the early radiation dominated Universe due to the spherical collapse of regions which have a large density perturbation at the horizon scale at that time. I will review the current status of constraints on PBHs with introducing my own bounds on PBHs in terms of gamma-rays, CMB, BBN, and Higgs phenomenology. I also introduce theoretical models to produce them including [abridged]
Date: Wed, 13.12.2017
Time: 14:00
Duration: 60 min
Location:HEPHY Library
Contact:Josef Pradler

Testing small scale gravitational wave detectors with dynamical mass distributions
Speaker:Dennis Raetzel (Vienna)
Abstract:The recent discovery of gravitational waves by LIGO created renewed interest in the investigation of alternative gravitational detector designs, such as small scale resonant detectors. In this talk, it is explained how proposed small scale detectors can be tested by generating dynamical gravitational near fields with appropriate distributions of moving masses. This opens up the possibility to evaluate detector proposals very early in the development phase and may help to progress quickly in their development.
Date: Thu, 14.12.2017
Time: 14:00
Duration: 60 min
Location:Arbeitsgruppe Gravitation, Währinger Strasse 17, Raum 218, 2. Stock, 1090 Wien
Contact:P.T. Chrusciel

The Supercurrent and Einstein equations in the Superconformal formulation
Speaker:Marine Samsonyan (CERN)
Abstract:This talk is about the generalization of Ferrara Zumino multiplet of currents for any 4d curved background using superconformal formalism. We give the three basic multiplets; the Einstein tensor, the scalar curvature and the supercurrents multiplet. We observe that the 1st component of the superfield, whose lowest component is the auxiliary field gives the (super)Einstein equations. Investigating the bosonic part of the conservation equation of supercurrents multiplet, we find a generalization of Callan-Coleman-Jackiw improved currents. At the end we use the curvature multiplets to find supersymmetric backgrounds and give some examples that exhibit agreement with existing results.
Date: Fri, 15.12.2017
Time: 15:00
Duration: 60 min
Location:SEM 136, TU Wien, Freihaus, 10th floor (Wiedner Hauptstr. 8-10, A-1040 Vienna)
Contact:Timm Wrase