Calendar of Physics Talks Vienna

CoQuS Colloquium Seminar Talk by Kishan Dholakia
Speaker:Kishan Dholakia (CoQuS)
Abstract:"Let Nothing slow you down: new directions in optical manipulation" For further information please visit www.coqus.at. The details of the talk will be announced the week before the Colloquium.
Date: Mon, 06.11.2017
Time: 16:30
Duration: 120 min
Location:Lise-Meitner Hörsaal, Strudelhofgasse 4, 1090 Vienna

Quantized cosmological space-times from Yang-Mills matrix models
Speaker:Harold Steinacker (Univ. Wien)
Abstract:We present simple solutions of IKKT-type matrix models describing quantized homogeneous and isotropic cosmologies with finite density of microstates and a resolved Big Bang (BB). The BB arises from a signature change of the effective metric on a fuzzy brane embedded in Lorentzian target space, in the presence of a quantized 4-volume form. The Hubble parameter is singular at the BB, and becomes small at late times. There is no singularity from the target space point of view. One solution describes a linear coasting cosmology at late times, which is remarkably close to observation. That solution consists of two sheets with opposite intrinsic chiralities, which are connected in a Euclidean pre-big bang era.
Date: Tue, 07.11.2017
Time: 14:00
Duration: 60 min
Location:TU Wien, Freihaus, SEM 136, 10. Stock, Wiedner Hauptstr. 8-10,1040 Wien
Contact:S. Fredenhagen, D. Grumiller

Small-x Resummation from Effective Field Theory
Speaker:Aditya Pathak (Univ. Wien)
Abstract:im Rahmen des Teilchenphysikseminars
Date: Tue, 07.11.2017
Time: 16:15
Duration: 60 min
Location:Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:A. Hoang, H. Neufeld

Bell's theorem for temporal order
Speaker:Caslav Brukner (Vienna)
Abstract:In general relativity causal relations between any pair of events is uniquely determined by locally predefined variables – the distribution of matter-energy degrees of freedom in the events’ past light-cone. Under the assumption of locally predefined causal order, agents performing freely chosen local operations on an initially local quantum state cannot violate Bell inequalities. However, superposition of massive objects can effectively lead to “entanglement” in the temporal order between groups of local operations, enabling the violation of the inequalities. This shows that temporal orders between events can be “indefinite” in non-classical space-times.
Date: Thu, 09.11.2017
Time: 13:30
Duration: 60 min
Location:Arbeitsgruppe Gravitation, Währinger Strasse 17, Raum 218, 2. Stock, 1090 Wien
Contact:P.T. Chrusciel

Background radiations in underground experiments
Speaker:Dr. Vitaly Kudryavtsev (University of Sheffield)
Abstract:Background radiations are known to pose a threat to high-sensitivity experiments for rare event searches, such as dark matter, neutrinoless double-beta decay and neutrino detectors. These radiations are caused by minute concentrations of radioactive isotopes in the detector components (including the detector sensitive volume itself) and surrounding materials. They can also be caused by cosmic-rays either underground by producing background events indistinguishable from the expected signal, or at the surface by activating materials that are used in the detector construction. In this talk, I will review mechanisms and computer codes for gamma-ray and neutron production and transport. I will also discuss the background due to cosmic rays including activation of materials at the surface. As an example of background rate calculations, I will briefly summarise the work of the LZ Collaboration.
Date: Thu, 09.11.2017
Time: 14:00
Duration: 60 min
Location:Seminar Room, Institute of High Energy Physics (HEPHY), Wohllebengasse 12-14, 1040 Wien
Contact:Holger Kluck

Mechanical on Chip Circulator
Speaker:Shabir Barzanjeh (Institute of Science and Technology (IST) )
Abstract:Nonreciprocal circuit elements form an integral part of modern measurement and communication systems. Nonreciprocal circuit elements form an integral part of modern measurement and communication systems. Mathematically they require breaking of time-reversal symmetry, typically achieved using magnetic materials and more recently using the quantum Hall effect, parametric permittivity modulation or Josephson nonlinearities. Here, we demonstrate an on-chip magnetic-free circulator based on reservoir engineered optomechanical interactions. Directional circulation is achieved with controlled phase-sensitive interference of six distinct electro-mechanical signal conversion paths. The presented circulator is compact, its silicon-on-insulator platform is compatible with both superconducting qubits and silicon photonics, and its noise performance is close to the quantum limit. With a high dynamic range, a tunable bandwidth of up to 30 MHz and an in-situ reconfigurability as beam splitter or wavelength converter, it could pave the way for superconducting qubit processors with integrated and multiplexed on-chip signal processing and readout.
Date: Fri, 10.11.2017
Time: 15:30
Location:Atominstitut, Hörsaal, Stadionallee 2, Wien 2
Contact:J. Majer