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- ItemHausdorff metric BV discontinuity of sweeping processes(Bristol : IOP Publ., 2016) Klein, Olaf; Recupero, VincenzoSweeping processes are a class of evolution differential inclusions arising in elastoplasticity and were introduced by J.J. Moreau in the early seventies. The solution operator of the sweeping processes represents a relevant example of rate independent operator. As a particular case we get the so called play operator, which is a typical example of a hysteresis operator. The continuity properties of these operators were studied in several works. In this note we address the continuity with respect to the strict metric in the space of functions of bounded variation with values in the metric space of closed convex subsets of a Hilbert space. We provide counterexamples showing that for all BV-formulations of the sweeping process the corresponding solution operator is not continuous when its domain is endowed with the strict topology of BV and its codomain is endowed with the L1-topology. This is at variance with the play operator which has a BV-extension that is continuous in this case.
- ItemChiral Spin Liquid Ground State in YBaCo3FeO7(College Park, Md. : APS, 2022) Schweika, W.; Valldor, M.; Reim, J.D.; Rößler, U.K.A chiral spin liquid state is discovered in the highly frustrated, noncentrosymmetric swedenborgite compound YBaCo3FeO7, a layered kagome system of hexagonal symmetry, by advanced polarized neutron scattering from a single domain crystalline sample. The observed diffuse magnetic neutron scattering has an antisymmetric property that relates to its specific chirality, which consists of three cycloidal waves perpendicular to the c axis, forming an entity of cylindrical symmetry. Chirality and symmetry agree with relevant antisymmetric exchanges arising from broken spatial parity. Applying a Fourier analysis to the chiral interference pattern, with distinction between kagome sites and the connecting trigonal interlayer sites of threefold symmetry, the chiral spin correlation function is determined. Characteristic chiral waves originate from the trigonal sites and extend over several periods in the kagome planes. The chiral spin liquid is remarkably stable at low temperatures despite strong antiferromagnetic spin exchange. The observation raises a challenge, since the commonly accepted ground states in condensed matter either have crystalline long-range order or form a quantum liquid. We show that, within the classical theory of magnetic order, a disordered ground state may arise from chirality. The present scenario, with antisymmetric exchange acting as a frustrating gauge background that stabilizes local spin lumps, is similar to the avoided phase transition in coupled gauge and matter fields for subnuclear particles.
- ItemIntercalant-mediated Kitaev exchange in Ag3LiIr2O6(College Park, MD : APS, 2022) Yadav, Ravi; Reja, Sahinur; Ray, Rajyavardhan; van den Brink, Jeroen; Nishimoto, Satoshi; Yazyev, Oleg V.The recently synthesized Ag3LiIr2O6 has been proposed as a Kitaev magnet in proximity to the quantum spin liquid phase. We explore its microscopic Hamiltonian and magnetic ground state using many-body quantum chemistry methods and exact diagonalization techniques. Our calculations establish a dominant bond dependent ferromagnetic Kitaev exchange between Ir sites and find that the inclusion of Ag 4d orbitals in the configuration interaction calculations strikingly enhances the Kitaev exchange. Furthermore, using exact diagonalization of the nearest-neighbor fully anisotropic J−K−Γ Hamiltonian, we obtain the magnetic phase diagram as a function of further neighbor couplings. We find that the antiferromagnetic off-diagonal coupling stabilizes long range order, but the structure factor calculations suggest that the material is very close to the quantum spin liquid phase and the ordered state can easily collapse into a liquid by small perturbations such as structural distortion or bond disorder.
- ItemRobust nuclear hyperpolarization driven by strongly coupled nitrogen vacancy centers(Melville, NY : American Inst. of Physics, 2021) Wunderlich, Ralf; Staacke, Robert; Knolle, Wolfgang; Abel, Bernd; Haase, Jürgen; Meijer, JanNuclear magnetic resonance techniques are widely used in the natural sciences but they lack sensitivity. Therefore, large sample volumes or long measurement times are necessary. In this work, we investigate the polarization of bulk 13C nuclei in a diamond above the thermal equilibrium at room temperature. Previously studied mechanisms utilize direct coupling to nitrogen vacancy centers or the additional assistance of substitutional nitrogen impurities for this purpose. We exploit strongly coupled nitrogen vacancy centers as polarization sources. We study two approaches to transfer the optically induced polarization of the electron spins of the nitrogen vacancy centers to nearby nuclear spins. First, the electron-nuclear polarization transfer is achieved by energy matching conditions or, second, by magnetic field sweeps inducing Landau–Zener-like transitions. Simulations according to a quantum mechanical system consisting of two coupled nitrogen vacancy centers and a weakly coupled 13C spin show an excellent agreement with the experimental data. Both approaches allow a reduction of the measurement time by roughly three orders of magnitude.
- ItemRobust homoclinic orbits in planar systems with Preisach hysteresis operator(Bristol : IOP Publ., 2016) Pimenov, Alexander; Rachinskii, DmitriiWe construct examples of robust homoclinic orbits for systems of ordinary differential equations coupled with the Preisach hysteresis operator. Existence of such orbits is demonstrated for the first time. We discuss a generic mechanism that creates robust homoclinic orbits and a method for finding them. An example of a homoclinic orbit in a population dynamics model with hysteretic response of the prey to variations of the predator is studied numerically.
- ItemError estimates for nonlinear reaction-diffusion systems involving different diffusion length scales(Bristol : IOP Publ., 2016) Reichelt, SinaWe derive quantitative error estimates for coupled reaction-diffusion systems, whose coefficient functions are quasi-periodically oscillating modeling the microstructure of the underlying macroscopic domain. The coupling arises via nonlinear reaction terms and we allow for different diffusion length scales, i.e. whereas some species have characteristic diffusion length of order 1 other species may diffuse with the order of the characteristic microstructure-length scale. We consider an effective system, which is rigorously obtained via two-scale convergence, and we derive quantitative error estimates.
- ItemSome remarks on a model for rate-independent damage in thermo-visco-elastodynamics(Bristol : IOP Publ., 2016) Lazzaroni, Giuliano; Rossi, Riccarda; Thomas, Marita; Toader, RodicaThis note deals with the analysis of a model for partial damage, where the rate- independent, unidirectional flow rule for the damage variable is coupled with the rate-dependent heat equation, and with the momentum balance featuring inertia and viscosity according to Kelvin-Voigt rheology. The results presented here combine the approach from Roubicek [1, 2] with the methods from Lazzaroni/Rossi/Thomas/Toader [3]. The present analysis encompasses, differently from [2], the monotonicity in time of damage and the dependence of the viscous tensor on damage and temperature, and, unlike [3], a nonconstant heat capacity and a time-dependent Dirichlet loading.
- ItemExcited state distribution and spin-effects in strong-field excitation of neutral Helium(Bristol : IOP Publ., 2015) Zimmermann, Henri; Eilzer, Sebastian; Eichmann, UlliWe investigated the principal quantum number n distribution of excited states resulting from the interaction of Helium with strong, short laser pulses. We find excellent agreement with predictions of the semiclassical frustrated tunneling ionization (FTI) model [1] as well as fully quantum mechanical calculations. Furthermore, the excitation process directly populates triplet excited states due to the breakdown of the Russel-Saunders coupling scheme for high orbital angular momentum l states of Helium, which are predominantly populated in the strong laser field.
- ItemSeeking celestial positronium with an OH-suppressed diffraction-limited spectrograph(Washington, DC : The Optical Society, 2021) Robertson, Gordon; Ellis, Simon; Yu, Qingshan; Bland-Hawthorn, Joss; Betters, Christopher; Roth, Martin; Leon-Saval, SergioCelestially, positronium (Ps) has been observed only through gamma-ray emission produced by its annihilation. However, in its triplet state, a Ps atom has a mean lifetime long enough for electronic transitions to occur between quantum states. This produces a recombination spectrum observable in principle at near IR wavelengths, where angular resolution greatly exceeding that of the gamma-ray observations is possible. However, the background in the near IR is dominated by extremely bright atmospheric hydroxyl (OH) emission lines. In this paper, we present the design of a diffraction-limited spectroscopic system using novel photonic components—a photonic lantern, OH fiber Bragg grating filters, and a photonic TIGER 2D pseudo-slit—to observe the Ps Balmer alpha line at 1.3122 µm for the first time, to our knowledge.
- ItemCold atoms in space: community workshop summary and proposed road-map(Berlin ; Heidelberg [u.a.] : Springer Open, 2022) Alonso, Iván; Alpigiani, Cristiano; Altschul, Brett; Araújo, Henrique; Arduini, Gianluigi; Arlt, Jan; Badurina, Leonardo; Balaž, Antun; Bandarupally, Satvika; Barish, Barry C.; Barone, Michele; Reguzzoni, Mirko; Richaud, Andrea; Riou, Isabelle; Rothacher, Markus; Roura, Albert; Ruschhaupt, Andreas; Sabulsky, Dylan O.; Safronova, Marianna; Saltas, Ippocratis D.; Bernabeu, Jose; Haehnelt, Martin; Salvi, Leonardo; Sameed, Muhammed; Saurabh, Pandey; Schäffer, Stefan; Schiller, Stephan; Schilling, Manuel; Schkolnik, Vladimir; Schlippert, Dennis; Schmidt, Piet O.; Schnatz, Harald; Hanımeli, Ekim T.; Bertoldi, Andrea; Schneider, Jean; Schneider, Ulrich; Schreck, Florian; Schubert, Christian; Shayeghi, Armin; Sherrill, Nathaniel; Shipsey, Ian; Signorini, Carla; Singh, Rajeev; Hawkins, Leonie; Singh, Yeshpal; Bingham, Robert; Skordis, Constantinos; Smerzi, Augusto; Sopuerta, Carlos F.; Sorrentino, Fiodor; Sphicas, Paraskevas; Stadnik, Yevgeny V.; Stefanescu, Petruta; Tarallo, Marco G.; Hees, Aurélien; Tentindo, Silvia; Tino, Guglielmo M.; Bize, Sébastien; Tinsley, Jonathan N.; Tornatore, Vincenza; Treutlein, Philipp; Trombettoni, Andrea; Tsai, Yu-Dai; Tuckey, Philip; Uchida, Melissa A.; Henderson, Victoria A.; Valenzuela, Tristan; Van Den Bossche, Mathias; Vaskonen, Ville; Blas, Diego; Verma, Gunjan; Vetrano, Flavio; Vogt, Christian; von Klitzing, Wolf; Waller, Pierre; Walser, Reinhold; Herr, Waldemar; Wille, Eric; Williams, Jason; Windpassinger, Patrick; Wittrock, Ulrich; Bongs, Kai; Wolf, Peter; Woltmann, Marian; Wörner, Lisa; Xuereb, André; Yahia, Mohamed; Herrmann, Sven; Yazgan, Efe; Yu, Nan; Zahzam, Nassim; Zambrini Cruzeiro, Emmanuel; Zhan, Mingsheng; Bouyer, Philippe; Zou, Xinhao; Zupan, Jure; Zupanič, Erik; Braitenberg, Carla; Hird, Thomas; Brand, Christian; Braxmaier, Claus; Bresson, Alexandre; Buchmueller, Oliver; Budker, Dmitry; Bugalho, Luís; Burdin, Sergey; Cacciapuoti, Luigi; Callegari, Simone; Calmet, Xavier; Hobson, Richard; Calonico, Davide; Canuel, Benjamin; Caramete, Laurentiu-Ioan; Carraz, Olivier; Cassettari, Donatella; Chakraborty, Pratik; Chattopadhyay, Swapan; Chauhan, Upasna; Chen, Xuzong; Chen, Yu-Ao; Hock, Vincent; Chiofalo, Maria Luisa; Coleman, Jonathon; Corgier, Robin; Cotter, J. P.; Michael Cruise, A.; Cui, Yanou; Davies, Gavin; De Roeck, Albert; Demarteau, Marcel; Derevianko, Andrei; Barsanti, Michele; Di Clemente, Marco; Djordjevic, Goran S.; Donadi, Sandro; Doré, Olivier; Dornan, Peter; Doser, Michael; Drougakis, Giannis; Dunningham, Jacob; Easo, Sajan; Eby, Joshua; Hogan, Jason M.; Elertas, Gedminas; Ellis, John; Evans, David; Examilioti, Pandora; Fadeev, Pavel; Fanì, Mattia; Fassi, Farida; Fattori, Marco; Fedderke, Michael A.; Felea, Daniel; Holst, Bodil; Feng, Chen-Hao; Ferreras, Jorge; Flack, Robert; Flambaum, Victor V.; Forsberg, René; Fromhold, Mark; Gaaloul, Naceur; Garraway, Barry M.; Georgousi, Maria; Geraci, Andrew; Holynski, Michael; Gibble, Kurt; Gibson, Valerie; Gill, Patrick; Giudice, Gian F.; Goldwin, Jon; Gould, Oliver; Grachov, Oleg; Graham, Peter W.; Grasso, Dario; Griffin, Paul F.; Israelsson, Ulf; Guerlin, Christine; Gündoğan, Mustafa; Gupta, Ratnesh K.; Jeglič, Peter; Jetzer, Philippe; Juzeliūnas, Gediminas; Kaltenbaek, Rainer; Kamenik, Jernej F.; Kehagias, Alex; Bass, Steven; Kirova, Teodora; Kiss-Toth, Marton; Koke, Sebastian; Kolkowitz, Shimon; Kornakov, Georgy; Kovachy, Tim; Krutzik, Markus; Kumar, Mukesh; Kumar, Pradeep; Lämmerzahl, Claus; Bassi, Angelo; Landsberg, Greg; Le Poncin-Lafitte, Christophe; Leibrandt, David R.; Lévèque, Thomas; Lewicki, Marek; Li, Rui; Lipniacka, Anna; Lisdat, Christian; Liu, Mia; Lopez-Gonzalez, J. L.; Battelier, Baptiste; Loriani, Sina; Louko, Jorma; Luciano, Giuseppe Gaetano; Lundblad, Nathan; Maddox, Steve; Mahmoud, M. A.; Maleknejad, Azadeh; March-Russell, John; Massonnet, Didier; McCabe, Christopher; Baynham, Charles F. A.; Meister, Matthias; Mežnaršič, Tadej; Micalizio, Salvatore; Migliaccio, Federica; Millington, Peter; Milosevic, Milan; Mitchell, Jeremiah; Morley, Gavin W.; Müller, Jürgen; Murphy, Eamonn; Beaufils, Quentin; Müstecaplıoğlu, Özgür E.; O’Shea, Val; Oi, Daniel K. L.; Olson, Judith; Pal, Debapriya; Papazoglou, Dimitris G.; Pasatembou, Elizabeth; Paternostro, Mauro; Pawlowski, Krzysztof; Pelucchi, Emanuele; Belić, Aleksandar; Pereira dos Santos, Franck; Peters, Achim; Pikovski, Igor; Pilaftsis, Apostolos; Pinto, Alexandra; Prevedelli, Marco; Puthiya-Veettil, Vishnupriya; Quenby, John; Rafelski, Johann; Rasel, Ernst M.; Bergé, Joel; Ravensbergen, CornelisWe summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies.