TY - JOUR A1 - Kegeles, Alexander A1 - Oriti, Daniele T1 - Generalized conservation laws in non-local field theories JF - Journal of physics : A, Mathematical and theoretical N2 - We propose a geometrical treatment of symmetries in non-local field theories, where the non-locality is due to a lack of identification of field arguments in the action. We show that the existence of a symmetry of the action leads to a generalized conservation law, in which the usual conserved current acquires an additional non-local correction term, obtaining a generalization of the standard Noether theorem. We illustrate the general formalism by discussing the specific physical example of complex scalar field theory of the type describing the hydrodynamic approximation of Bose-Einstein condensates. We expect our analysis and results to be of particular interest for the group field theory formulation of quantum gravity. KW - conservation laws KW - non-local field theory KW - Noether theorem KW - group field theory Y1 - 2016 U6 - https://doi.org/10.1088/1751-8113/49/13/135401 SN - 1751-8113 SN - 1751-8121 VL - 49 SP - 119 EP - 134 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Mazurek, P. A1 - Yu, L. A1 - Gerhard, Reimund A1 - Wirges, Werner A1 - Skov, A. L. T1 - Glycerol as high-permittivity liquid filler in dielectric silicone elastomers JF - Journal of applied polymer science N2 - A recently reported novel class of elastomers was tested with respect to its dielectric properties. The new elastomer material is based on a commercially available poly(dimethylsiloxane) composition, which has been modified by embedding glycerol droplets into its matrix. The approach has two major advantages that make the material useful in a dielectric actuator. First, the glycerol droplets efficiently enhance the dielectric constant, which can reach astonishingly high values in the composite. Second, the liquid filler also acts as a softener that effectively decreases the elastic modulus of the composite. In combination with very low cost and easy preparation, the two property enhancements lead to an extremely attractive dielectric elastomer material. Experimental permittivity data are compared to various theoretical models that predict relative permittivity changes as a function of filler loading, and the applicability of the models is discussed. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44153. KW - crosslinking KW - dielectric properties KW - elastomers KW - sensors and actuators Y1 - 2016 U6 - https://doi.org/10.1002/app.44153 SN - 0021-8995 SN - 1097-4628 VL - 133 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Pavlenko, Elena S. A1 - Sander, Mathias A1 - Cui, Q. A1 - Bargheer, Matias T1 - Gold Nanorods Sense the Ultrafast Viscoelastic Deformation of Polymers upon Molecular Strain Actuation JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - On the basis of the layer-by-layer deposition of polyelectrolytes, we have designed hybrid nanolayer composites for integrated optoacoustic experiments. The femtosecond-laser-excitation of an Azo functionalized film launches nanoscale strain waves at GHz frequencies into a transparent polymer layer. Gold nanorods deposited on the surface sense the arrival of these hyper-sound-waves on the picosecond time scale via a modification of their longitudinal plasmon resonance. We simulated the strain waves using a simple linear masses-and-springs model, which yields good agreement with the observed time scales associated with the nanolayer thicknesses of the constituent materials. From systematic experiments with calibrated strain amplitudes we conclude that reversible viscoelastic deformations of the polyelectrolyte multilayers are triggered by ultrashort pressure transients of about 4 MPa. Our experiments show that strain-mediated interactions in nanoarchitectures composed of molecular photoswitches and plasmonic particles may be used to design new functionalities. The approach combines the highly flexible and cost-effective preparation of polyelectrolyte multilayers with ultrafast molecular strain actuation and plasmonic sensing. Although we use simple flat layered structures for demonstration, this new concept can be used for three-dimensional nanoassemblies with different functionalities. The ultrafast and reversible nature of the response is highly desirable, and the short wavelength associated with the high frequency of the hyper-sound-waves connecting photoactive molecules and nanoparticles inherently gives spectroscopic access to the nanoscale. High-frequency elastic moduli are derived from the ultrafast spectroscopy of the hypersonic response in polyelectrolyte multilayers. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jpcc.6b06915 SN - 1932-7447 VL - 120 SP - 24957 EP - 24964 PB - American Chemical Society CY - Washington ER - TY - GEN A1 - Rätzel, Dennis A1 - Wilkens, Martin A1 - Menzel, Ralf T1 - Gravitational properties of light BT - the gravitational field of a laser pulse N2 - The gravitational field of a laser pulse of finite lifetime, is investigated in the framework of linearized gravity. Although the effects are very small, they may be of fundamental physical interest. It is shown that the gravitational field of a linearly polarized light pulse is modulated as the norm of the corresponding electric field strength, while no modulations arise for circular polarization. In general, the gravitational field is independent of the polarization direction. It is shown that all physical effects are confined to spherical shells expanding with the speed of light, and that these shells are imprints of the spacetime events representing emission and absorption of the pulse. Nearby test particles at rest are attracted towards the pulse trajectory by the gravitational field due to the emission of the pulse, and they are repelled from the pulse trajectory by the gravitational field due to its absorption. Examples are given for the size of the attractive effect. It is recovered that massless test particles do not experience any physical effect if they are co-propagating with the pulse, and that the acceleration of massless test particles counter-propagating with respect to the pulse is four times stronger than for massive particles at rest. The similarities between the gravitational effect of a laser pulse and Newtonian gravity in two dimensions are pointed out. The spacetime curvature close to the pulse is compared to that induced by gravitational waves from astronomical sources. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 222 KW - electromagnetic radiation KW - general relativity KW - gravity KW - laser pulses KW - linearized gravity KW - pp-wave solutions Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-90553 ER - TY - JOUR A1 - Rätzel, Dennis A1 - Wilkens, Martin A1 - Menzel, Ralf T1 - Gravitational properties of light BT - the gravitational field of a laser pulse JF - New journal of physics : the open-access journal for physics N2 - The gravitational field of a laser pulse of finite lifetime, is investigated in the framework of linearized gravity. Although the effects are very small, they may be of fundamental physical interest. It is shown that the gravitational field of a linearly polarized light pulse is modulated as the norm of the corresponding electric field strength, while no modulations arise for circular polarization. In general, the gravitational field is independent of the polarization direction. It is shown that all physical effects are confined to spherical shells expanding with the speed of light, and that these shells are imprints of the spacetime events representing emission and absorption of the pulse. Nearby test particles at rest are attracted towards the pulse trajectory by the gravitational field due to the emission of the pulse, and they are repelled from the pulse trajectory by the gravitational field due to its absorption. Examples are given for the size of the attractive effect. It is recovered that massless test particles do not experience any physical effect if they are co-propagating with the pulse, and that the acceleration of massless test particles counter-propagating with respect to the pulse is four times stronger than for massive particles at rest. The similarities between the gravitational effect of a laser pulse and Newtonian gravity in two dimensions are pointed out. The spacetime curvature close to the pulse is compared to that induced by gravitational waves from astronomical sources. KW - gravity KW - general relativity KW - laser pulses KW - electromagnetic radiation KW - linearized gravity KW - pp-wave solutions Y1 - 2016 U6 - https://doi.org/10.1088/1367-2630/18/2/023009 SN - 1367-2630 VL - 18 SP - 1 EP - 16 PB - IOP Science CY - London ER - TY - JOUR A1 - Rätzel, Dennis A1 - Wilkens, Martin A1 - Menzel, Ralf T1 - Gravitational properties of light-the gravitational field of a laser pulse JF - NEW JOURNAL OF PHYSICS N2 - The gravitational field of a laser pulse of finite lifetime, is investigated in the framework of linearized gravity. Although the effects are very small, they may be of fundamental physical interest. It is shown that the gravitational field of a linearly polarized light pulse is modulated as the norm of the corresponding electric field strength, while no modulations arise for circular polarization. In general, the gravitational field is independent of the polarization direction. It is shown that all physical effects are confined to spherical shells expanding with the speed of light, and that these shells are imprints of the spacetime events representing emission and absorption of the pulse. Nearby test particles at rest are attracted towards the pulse trajectory by the gravitational field due to the emission of the pulse, and they are repelled from the pulse trajectory by the gravitational field due to its absorption. Examples are given for the size of the attractive effect. It is recovered that massless test particles do not experience any physical effect if they are co-propagating with the pulse, and that the acceleration of massless test particles counter-propagating with respect to the pulse is four times stronger than for massive particles at rest. The similarities between the gravitational effect of a laser pulse and Newtonian gravity in two dimensions are pointed out. The spacetime curvature close to the pulse is compared to that induced by gravitational waves from astronomical sources. KW - gravity KW - general relativity KW - laser pulses KW - electromagnetic radiation KW - linearized gravity KW - pp-wave solutions Y1 - 2016 U6 - https://doi.org/10.1088/1367-2630/18/2/023009 SN - 1367-2630 VL - 18 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Schreck, Simon A1 - Pietzsch, Annette A1 - Kennedy, Brian A1 - Sathe, Conny A1 - Miedema, Piter S. A1 - Techert, Simone A1 - Strocov, Vladimir N. A1 - Schmitt, Thorsten A1 - Hennies, Franz A1 - Rubensson, Jan-Erik A1 - Föhlisch, Alexander T1 - Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering JF - Scientific reports N2 - Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future. Y1 - 2016 U6 - https://doi.org/10.1038/srep20054 SN - 2045-2322 VL - 6 PB - Nature Publ. Group CY - London ER - TY - THES A1 - Bendre, Abhijit B. T1 - Growth and saturation of dynamo in spiral galaxies via direct simulations T1 - Wachstum und Sättigung des Dynamos in Spiralgalaxien mit direkten Simulationen N2 - We do magnetohydrodynamic (MHD) simulations of local box models of turbulent Interstellar Medium (ISM) and analyse the process of amplification and saturation of mean magnetic fields with methods of mean field dynamo theory. It is shown that the process of saturation of mean fields can be partially described by the prolonged diffusion time scales in presence of the dynamically significant magnetic fields. However, the outward wind also plays an essential role in the saturation in higher SN rate case. Algebraic expressions for the back reaction of the magnetic field onto the turbulent transport coefficients are derived, which allow a complete description of the nonlinear dynamo. We also present the effects of dynamically significant mean fields on the ISM configuration and pressure distribution. We further add the cosmic ray component in the simulations and investigate the kinematic growth of mean fields with a dynamo perspective. N2 - Wir fuehren magnetohydrodynamische (MHD) Simulationen des turbulenten interstellaren Mediums (ISM) in lokalen Boxen durch und analysieren darin den Prozess der Verstaerkung und Saturation der mittleren Magnetfelder mit Methoden der Dynamotheorie mittlerer Felder. Es wird gezeigt, dass der Prozess der Saturation mittlerer Felder teilweise durch eine verlaengerte Diffusionzeit in Gegenwart dynamisch signifikanter Magnetfelder erklaert werden kann. Fuer hoehere Supernovae-Raten spielt auch der nach aussen treibende Wind eine essenzielle Rolle fuer die Saturation. Aus den Simulationen konnten algebraische Formeln fuer die Rueckwirkung des Magnetfeldes auf die turbulenten Transportkoeffizienten abgeleitet werden, die eine vollstaendige Beschreibung des nichtlinearen Dynamos erlauben. Wir praesentieren zudem den Einfluss signifikanter mittlerer Magnetfelder auf die ISM-Konfiguration und Druckverteilung. Wir fuegen der Simulation ausserdem kosmische Strahlung als Komponente hinzu und untersuchen das kinematische Wachstum mittlerer Felder aus einer Dynamo-Perspektive. KW - magnetohydrodynamics KW - ISM: Turbulence KW - spiral galaxies: magnetic fields KW - nonliear dynamo KW - cosmic ray dynamo KW - Magnetohydrodynamik KW - ISM: Turbulenz KW - Spiralgalaxien: Magnetfelder KW - nichtlineare Dynamo KW - kosmische Strahlung Dynamo Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-407517 ER - TY - JOUR A1 - Hassanin, Alshaimaa A1 - Kliem, Bernhard A1 - Seehafer, Norbert T1 - Helical kink instability in the confined solar eruption on 2002 May 27 JF - Astronomische Nachrichten = Astronomical notes KW - instabilities KW - magnetohydrodynamics (MHD) KW - Sun: corona KW - Sun: coronal mass ejections (CMEs) KW - Sun: flares Y1 - 2016 U6 - https://doi.org/10.1002/asna.201612446 SN - 0004-6337 SN - 1521-3994 VL - 337 SP - 1082 EP - 1089 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Abdalla, Hassan E. A1 - Abramowski, Attila A1 - Aharonian, Felix A. A1 - Benkhali, Faical Ait A1 - Akhperjanian, A. G. A1 - Andersson, T. A1 - Angüner, Ekrem Oǧuzhan A1 - Arrieta, M. A1 - Aubert, Pierre A1 - Backes, Michael A1 - Balzer, Arnim A1 - Barnard, Michelle A1 - Becherini, Yvonne A1 - Tjus, J. Becker A1 - Berge, David A1 - Bernhard, Sabrina A1 - Bernlöhr, K. A1 - Birsin, E. A1 - Blackwell, R. A1 - Boettcher, Markus A1 - Boisson, Catherine A1 - Bolmont, J. A1 - Bordas, Pol A1 - Bregeon, Johan A1 - Brun, Francois A1 - Brun, Pierre A1 - Bryan, Mark A1 - Bulik, Tomasz A1 - Capasso, M. A1 - Carr, John A1 - Casanova, Sabrina A1 - Chakraborty, N. A1 - Chalme-Calvet, R. A1 - Chaves, Ryan C. G. A1 - Chen, Andrew A1 - Chevalier, J. A1 - Chretien, M. A1 - Colafrancesco, Sergio A1 - Cologna, Gabriele A1 - Condon, B. A1 - Conrad, Jan A1 - Couturier, C. A1 - Cui, Y. A1 - Davids, I. D. A1 - Degrange, B. A1 - Deil, C. A1 - Devin, J. A1 - de Wilt, P. A1 - Djannati-Ataie, A. A1 - Domainko, W. A1 - Donath, A. A1 - Dubus, G. A1 - Dutson, K. A1 - Dyks, J. A1 - Dyrda, M. A1 - Edwards, T. A1 - Egberts, Kathrin A1 - Eger, P. A1 - Ernenwein, J. -P. A1 - Eschbach, S. A1 - Farnier, C. A1 - Fegan, S. A1 - Fernandes, M. V. A1 - Fiasson, A. A1 - Fontaine, G. A1 - Foerster, A. A1 - Funk, S. A1 - Fuessling, M. A1 - Gabici, S. A1 - Gajdus, M. A1 - Gallant, Y. A. A1 - Garrigoux, T. A1 - Giavitto, G. A1 - Giebels, B. A1 - Glicenstein, J. F. A1 - Gottschall, D. A1 - Goyal, A. A1 - Grondin, M. -H. A1 - Grudzinska, M. A1 - Hadasch, D. A1 - Hahn, J. A1 - Hawkes, J. A1 - Heinzelmann, G. A1 - Henri, G. A1 - Hermann, G. A1 - Hervet, O. A1 - Hillert, A. A1 - Hinton, James Anthony A1 - Hofmann, W. A1 - Hoischen, Clemens A1 - Holler, M. A1 - Horns, D. A1 - Ivascenko, A. A1 - Jacholkowska, A. A1 - Jamrozy, M. A1 - Janiak, M. A1 - Jankowsky, D. A1 - Jankowsky, F. A1 - Jingo, M. A1 - Jogler, T. A1 - Jouvin, L. A1 - Jung-Richardt, I. A1 - Kastendieck, M. A. A1 - Katarzynski, K. A1 - Katz, U. A1 - Kerszberg, D. A1 - Khelifi, B. A1 - Kieffer, M. A1 - King, J. A1 - Klepser, S. A1 - Klochkov, D. A1 - Kluzniak, W. A1 - Kolitzus, D. A1 - Komin, Nu. A1 - Kosack, K. A1 - Krakau, S. A1 - Kraus, M. A1 - Krayzel, F. A1 - Krueger, P. P. A1 - Laffon, H. A1 - Lamanna, G. A1 - Lau, J. A1 - Lees, J. -P. A1 - Lefaucheur, J. A1 - Lefranc, V. A1 - Lemiere, A. A1 - Lemoine-Goumard, M. A1 - Lenain, J. -P. A1 - Leser, Eva A1 - Liu, R. A1 - Lohse, T. A1 - Lorentz, M. A1 - Lypova, I. A1 - Marandon, V. A1 - Marcowith, Alexandre A1 - Mariaud, C. A1 - Marx, R. A1 - Maurin, G. A1 - Maxted, N. A1 - Mayer, Michael A1 - Meintjes, P. J. A1 - Meyer, M. A1 - Mitchell, A. M. W. A1 - Moderski, R. A1 - Mohamed, M. A1 - Mora, K. A1 - Moulin, Emmanuel A1 - Murach, T. A1 - de Naurois, M. A1 - Niederwanger, F. A1 - Niemiec, J. A1 - Oakes, L. A1 - Odaka, H. A1 - Ohm, S. A1 - Ostrowski, M. A1 - Oettl, S. A1 - Oya, I. A1 - Padovani, M. A1 - Panter, M. A1 - Parsons, R. D. A1 - Arribas, M. Paz A1 - Pekeur, N. W. A1 - Pelletier, G. A1 - Perennes, C. A1 - Petrucci, P. -O. A1 - Peyaud, B. A1 - Pita, S. A1 - Poon, H. A1 - Prokhorov, D. A1 - Prokoph, H. A1 - Puehlhofer, G. A1 - Punch, M. A1 - Quirrenbach, A. A1 - Raab, S. A1 - Reimer, A. A1 - Reimer, O. A1 - Renaud, M. A1 - Reyes, R. de los A1 - Rieger, F. A1 - Romoli, C. A1 - Rosier-Lees, S. A1 - Rowell, G. A1 - Rudak, B. A1 - Rulten, C. B. A1 - Sahakian, V. A1 - Salek, D. A1 - Sanchez, David M. A1 - Santangelo, A. A1 - Sasaki, M. A1 - Schlickeiser, R. A1 - Schuessler, F. A1 - Schulz, A. A1 - Schwanke, U. A1 - Schwemmer, S. A1 - Settimo, M. A1 - Seyffert, A. S. A1 - Shafi, N. A1 - Shilon, I. A1 - Simoni, R. A1 - Sol, H. A1 - Spanier, F. A1 - Spengler, G. A1 - Spies, F. A1 - Stawarz, L. A1 - Steenkamp, R. A1 - Stegmann, Christian A1 - Stinzing, F. A1 - Stycz, K. A1 - Sushch, Iurii A1 - Tavernet, J. -P. A1 - Tavernier, T. A1 - Taylor, A. M. A1 - Terrier, R. A1 - Tibaldo, L. A1 - Tluczykont, M. A1 - Trichard, C. A1 - Tuffs, R. A1 - van der Walt, J. A1 - van Eldik, C. A1 - van Soelen, B. A1 - Vasileiadis, G. A1 - Veh, J. A1 - Venter, C. A1 - Viana, A. A1 - Vincent, P. A1 - Vink, J. A1 - Voisin, F. A1 - Voelk, H. J. A1 - Vuillaume, T. A1 - Wadiasingh, Z. A1 - Wagner, S. J. A1 - Wagner, P. A1 - Wagner, R. M. A1 - White, R. A1 - Wierzcholska, A. A1 - Willmann, P. A1 - Woernlein, A. A1 - Wouters, D. A1 - Yang, R. A1 - Zabalza, V. A1 - Zaborov, D. A1 - Zacharias, M. A1 - Zdziarski, A. A. A1 - Zech, Alraune A1 - Zefi, F. A1 - Ziegler, A. A1 - Zywucka, N. T1 - HESS Limits on Linelike Dark Matter Signatures in the 100 GeV to 2 TeV Energy Range Close to the Galactic Center JF - Physical review letters N2 - A search for dark matter linelike signals iss performed in the vicinity of the Galactic Center by the H.E.S.S. experiment on observational data taken in 2014. An unbinned likelihood analysis iss developed to improve the sensitivity to linelike signals. The upgraded analysis along with newer data extend the energy coverage of the previous measurement down to 100 GeV. The 18 h of data collected with the H.E.S.S. array allow one to rule out at 95% C.L. the presence of a 130 GeV line (at l = -1.5 degrees, b = 0 degrees and for a dark matter profile centered at this location) previously reported in Fermi-LAT data. This new analysis overlaps significantly in energy with previous Fermi-LAT and H.E.S.S. results. No significant excess associated with dark matter annihilations was found in the energy range of 100 GeV to 2 TeV and upper limits on the gamma-ray flux and the velocity weighted annihilation cross section are derived adopting an Einasto dark matter halo profile. Expected limits for present and future large statistics H.E.S.S. observations are also given. Y1 - 2016 U6 - https://doi.org/10.1103/PhysRevLett.117.151302 SN - 0031-9007 SN - 1079-7114 VL - 117 PB - American Physical Society CY - College Park ER -