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Calendar of Physics Talks Vienna
| On extensions of CMC-Bartnik data |
| Speaker: | Carla Cederbaum (Univ. Tübingen) |
| Abstract: | Bartnik data are a Riemannian 2-sphere of positive Gaussian curvature equipped with a non-negative function H to be thought of as its mean curvature in an ambient Riemannian 3-manifold. Mantoulidis and Schoen suggested a construction of asymptotically flat Riemannian 3-manifolds of non-negative scalar curvature which allows to isometrically embed given Bartnik data of vanishing mean curvature, i.e. H=0. They use their construction to explore — and disprove — stability of the Riemannian Penrose inequality. In collaboration with Cabrera Pacheco, McCormick, and Miao, we adapt their construction to constant mean curvature (CMC) Bartnik data, i.e. H=const.>0. Moreover, with Cabrera Pacheco and McCormick, we extend their construction to the asymptotically hyperbolic setting both for H=0 and for H=const.>0 Bartnik data. I will present the construction as well as the motivation for such a . . . |
| Date: | Mon, 25.06.2018 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Arbeitsgruppe Gravitation, Währinger Strasse 17, Raum 218, 2. Stock, 1090 Wien |
| Contact: | P.T. Chrusciel, D. Fajman |
| Fourfolds, integral Fluxes and Modularity |
| Speaker: | Thorsten Schimannek (Univ. Bonn) |
| Abstract: | Four-dimensional N=1 vacua of F-theory are determined by three discrete choices.
A topological type of elliptically fibered Calabi-Yau fourfolds, a choice of flux and
a minimum of the corresponding scalar potential. While there are several constructions that together provide an abundance of elliptic Calabi-Yaus, the choice of properly quantized flux is in general more involved. The talk will start with a brief review of
F-theory and the geometry of Calabi-Yau fourfolds. I will then explain how topological string theory and homological mirror symmetry can be used to determine properly quantized choices for a particular class of fluxes. Additional comments will be about certain Fourier-Mukai transformations that act on the underlying basis of topological branes and lead to modular properties of the Gromov-Witten potentials on non-singular Calabi-Yau fourfolds.
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| Date: | Tue, 26.06.2018 |
| Time: | 13:45 |
| Duration: | 60 min |
| Location: | TU Wien, Freihaus, SEM 136, 10. Stock, Wiedner Hauptstr. 8-10, 1040 Wien |
| Contact: | S. Fredenhagen, D. Grumiller, J. Knapp |
| Adsorption, Structure and Optical Properties of Organic Molecules on Surfaces |
| Speaker: | Peter Zeppenfeld (Institute of Experimental Physics, Johannes Kepler University Linz) |
| Abstract: |
Controlling the electronic and optical properties of organic thin films is of both fundamental and technological interest. These functional properties are strongly correlated with the structural ordering and orientation of the adsorbed molecules, which can be influenced by the choice of the substrate or its preparation. I will illustrate experimental approaches to characterize and manipulate the adsorption and growth of organic thin films under well-defined conditions (ultra-high vacuum) and on atomically flat and clean substrates. This “surface science approach” aims at exploring the fundamental aspects of molecular self-assembly, quantifying the underlying interactions and understanding the structure-property relationship. Besides conventional surface science techniques, like scanning probe microscopy, surface diffraction and electron microscopy/spectroscopy, I will also introduce optical methods, namely Reflectance Difference Spectroscopy (RDS/RAS) and Differential Reflectance Spectroscopy (DRS), which can provide valuable insight into the structure and growth of ultrathin films in straight correlation with their electronic, optical and other physical or chemical properties. Notably, these differential optical spectroscopies can achieve sub-monolayer sensitivity and are capable of monitoring kinetic processes on surfaces in real time.
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| Date: | Tue, 26.06.2018 |
| Time: | 14:30 |
| Location: | Atominstitut, Seminarraum, Stadionallee 2, Wien 2 |
| Contact: | Arno Rauschenbeutel |
| A numerical formulation of resummation in effective field theory |
| Speaker: | Pier Monni (CERN) |
| Abstract: | I show how the resummation of infrared and collinear logarithms within Soft-Collinear Effective Theory (SCET) can be formulated in a way that makes it suitable for a Monte-Carlo implementation. This is done by applying the techniques developed for automated resummation using the branching formalism, which have resulted in the general resummation approach CAESAR/ARES. This work builds a connection between the two resummation approaches, and paves the way to automated resummation in SCET. As a case study I consider the resummation of the thrust distribution in electron-positron collisions at next-to-leading logarithm (NLL), and discuss the extension to more complicated observables and processes as well as to higher orders in the logarithmic accuracy. |
| Date: | Tue, 26.06.2018 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock |
| Contact: | A. Hoang, M. Procura |
| Organic molecules for integrated quantum photonics |
| Speaker: | Sofia Pazzagli (University of Florence LENS ) |
| Abstract: | The efficient integration of single-photon emitters into photonic structures - such as photonic cavities or waveguides - is crucial for a range of quantum information pro-cessing applications. Among solid-state quantum emitters, organic molecules in crystal-line matrices are promising single-photon sources, owing to their bright, stable and lifetime-limited emission at cryogenic temperatures. However, with respect to the more studied quantum dots and colour centres in diamonds, little progress has been made in manipulation and nanofabrication techniques available for organic materials, limiting the integration strategies of single molecules in complex photonics structures.
In this talk I will first show, both numerically and experimentally, that single photons from dibenzoterrylene (DBT) molecules in anthracene crystals (Ac) simply spin-coated onto dielectric waveguides can be evanescently coupled to on-chip guided modes with an efficiency as high as 40%. I will then report on the single-photon emis-sion properties of DBT molecules embedded in sub-micrometric Ac crystals grown with a simple and versatile fabrication protocol. The compatibility of these organic nano-crystals with different polymeric matrices and their lithographic techniques is finally discussed, relying on on-going experimental results, as a promising strategy for the integration of fluorescent molecules in future realistic quantum technologies.
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| Date: | Wed, 27.06.2018 |
| Time: | 14:30 |
| Location: | Atominstitut, Seminarraum, Stadionallee 2, Wien 2 |
| Contact: | Arno Rauschenbeutel |
| Global analysis for linear and nonlinear waves and the stability of Kerr-de Sitter space |
| Speaker: | Andras Vasy (Standford) |
| Abstract: | I will discuss the problem of proving the stability of the family of Kerr-de Sitter (KdS) black holes as solutions of Einstein's vacuum equation: spacetimes evolving from initial data close to those of $(M,g)$ stay globally close to $(M,g)$, and are indeed asymptotic to $(M,g)$ or another nearby member of the KdS family.
I will focus on analytic aspects of this problem together with the choice of a gauge to break the diffeomorphism invariance of Einstein's equation and the role of constraint damping. The analytic framework is that of global non-elliptic Fredholm problems. The main ingredients are, first, the microlocal control of the regularity of waves by means of elliptic, real principal type, and radial point estimates on a suitable compactification of the spacetime; and second, the asymptotic analysis in which model operators and resonance expansions play a role.
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| Date: | Fri, 29.06.2018 |
| Time: | 15:00 |
| Duration: | 60 min |
| Location: | Erwin-Schrödinger-Institut, Boltzmanngasse 9, Schrödinger Lecture Hall, 2. Stock |
| Contact: | A. Cap, P. T. Chrusciel, R. Donninger, M. Eichmair, M. Kunzinger |
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