Results for "R. A. Beyer"

total 275326took 0.14s
Investigation of thin n-in-p planar pixel modules for the ATLAS upgradeSep 16 2016In view of the High Luminosity upgrade of the Large Hadron Collider (HL-LHC), planned to start around 2023-2025, the ATLAS experiment will undergo a replacement of the Inner Detector. A higher luminosity will imply higher irradiation levels and hence ... More
Results on the spectrum of R-Modes of slowly rotating relativistic starsMar 12 2002The paper considers the spectrum of axial perturbations of slowly uniformly rotating general relativistic stars in the framework of Y. Kojima. In a first step towards a full analysis only the evolution equations are treated but not the constraint. Then ... More
On the stability of the Kerr metricAug 16 2000The reduced (in the angular coordinate $\phi$) wave equation and Klein-Gordon equation are considered on a Kerr background and in the framework of $C^{0}$-semigroup theory. Each equation is shown to have a well-posed initial value problem,i.e., to have ... More
A new result on the Klein-Gordon equation in the background of a rotating black holeFeb 26 2008This short paper should serve as basis for further analysis of a previously found new symmetry of the solutions of the wave equation in the gravitational field of a Kerr black hole. Its main new result is the proof of essential self-adjointness of the ... More
Remarks on the relation between physics and faithNov 10 2006It is a quite common view among people, that are not aware of the developments in modern physics, that it is part of human nature to substitute religious faith in places where there is no knowledge. Therefore, an increase in knowledge would lead to a ... More
Beyond partial differential equations: A course on linear and quasi-linear abstract hyperbolic evolution equationsOct 21 2005May 06 2007This course introduces the use of semigroup methods in the solution of linear and nonlinear (quasi-linear) hyperbolic partial differential equations, with particular application to wave equations and Hermitian hyperbolic systems. Throughout the course ... More
On the Completeness of the Quasinormal Modes of the Poeschl-Teller PotentialMar 10 1998The completeness of the quasinormal modes of the wave equation with Poeschl-Teller potential is investigated. A main result is that after a large enough time $t_0$, the solutions of this equation corresponding to $C^{\infty}$-data with compact support ... More
A framework for perturbations and stability of differentially rotating starsJul 24 2000The paper provides a new framework for the description of linearized adiabatic lagrangian perturbations and stability of differentially rotating newtonian stars. In doing so it overcomes problems in a previous framework by Dyson and Schutz and provides ... More
On the characterization of asymptotic cases of the diffusion equation with rough coefficients and applications to preconditioningFeb 04 2009We consider the diffusion equation in the setting of operator theory. In particular, we study the characterization of the limit of the diffusion operator for diffusivities approaching zero on a subdomain $\Omega_1$ of the domain of integration of $\Omega$. ... More
On a new symmetry of the solutions of the wave equation in the background of a Kerr black holeJul 18 2006This short paper derives the constant of motion of a scalar field in the gravitational field of a Kerr black hole which is associated to a Killing tensor of that space-time. In addition, there is found a related new symmetry operator S for the solutions ... More
Results on the diffusion equation with rough coefficientsOct 19 2008We study the behaviour of the solutions of the stationary diffusion equation as a function of a possibly rough ($L^{\infty}$-) diffusivity. This includes the boundary behaviour of the solution maps, associating to each diffusivity the solution corresponding ... More
Quantitative High-Resolution Transmission Electron Microscopy of Single AtomsSep 13 2010Sep 20 2011Single atoms can be considered as basic objects for electron microscopy to test the microscope performance and basic concepts for modeling of image contrast. In this work high-resolution transmission electron microscopy was applied to image single platinum ... More
In-medium nucleon-nucleon potentials in configuration spaceJul 05 2001Based on the thermodynamic Green function approach two-nucleon correlations in nuclear matter at finite temperatures are revisited. To this end, we derive phase equivalent effective $r$-space potentials that include the effect of the Pauli blocking at ... More
The in-medium few-body problemAug 31 2004We are concerned with few-particle correlations in a fermionic system at finite temperature and density. Within the many-body Green functions formalism the description of correlations is provided by the Dyson equation approach that leads to effective ... More
Investigation of thin n-in-p planar pixel modules for the ATLAS upgradeSep 16 2016Nov 28 2016In view of the High Luminosity upgrade of the Large Hadron Collider (HL-LHC), planned to start around 2023-2025, the ATLAS experiment will undergo a replacement of the Inner Detector. A higher luminosity will imply higher irradiation levels and hence ... More
Evolution of ferroelectricity in tetrathiafulvalene-p-chloranil as a function of pressure and temperatureDec 24 2013Jun 24 2014The neutral-to-ionic phase transition in the mixed-stack charge-transfer complex tetrathiafulvalene-p-chloranil (TTF-CA) has been studied by pressure-dependent infrared spectroscopy up to p=11 kbar and down to low temperatures, T = 10 K. By tracking the ... More
Spin-polarized tunneling spectroscopic studies of the intrinsic heterogeneity and pseudogap phenomena in colossal magnetoresistive manganite La_{0.7}Ca_{0.3}MnO_{3}Apr 09 2010Nov 10 2010Spatially resolved tunneling spectroscopic studies of colossal magnetoresistive (CMR) manganite $\rm La_{0.7}Ca_{0.3}MnO_3$ (LCMO) epitaxial films on $\rm (LaAlO_3)_{0.3}(Sr_2AlTaO_6)_{0.7}$ substrate are investigated as functions of temperature, magnetic ... More
Experimental study of the electric dipole strength in the even Mo nuclei and its deformation dependenceJan 21 2010Two methods based on bremsstrahlung were applied to the stable even Mo isotopes for the experimental determination of the photon strength function covering the high excitation energy range above 4 MeV with its increasing level density. Photon scattering ... More
On the r-mode spectrum of relativistic starsMar 05 1999We present a mathematically rigorous proof that the r-mode spectrum of relativistic stars to the rotational lowest order has a continuous part. A rigorous definition of this spectrum is given in terms of the spectrum of a continuous linear operator. This ... More
On the Quasi-Periodic Oscillations of MagnetarsFeb 09 2009Feb 11 2009We study torsional Alfv\'en oscillations of magnetars, i.e., neutron stars with a strong magnetic field. We consider the poloidal and toroidal components of the magnetic field and a wide range of equilibrium stellar models. We use a new coordinate system ... More
Pressure-dependent optical investigations of $α$-(BEDT-TTF)$_2$I$_3$: tuning charge order and narrow gap towards a Dirac semimetalJan 19 2016Mar 24 2016Infrared optical investigations of $\alpha$-(BEDT-TTF)$_2$I$_3$ have been performed in the spectral range from 80 to 8000~cm$^{-1}$ down to temperatures as low as 10~K by applying hydrostatic pressure. In the metallic state, $T > 135$~K, we observe a ... More
Experimental investigation of the asymmetric spectroscopic characteristics of electron- and hole-doped cupratesMay 04 2004Quasiparticle tunneling spectroscopic studies of electron- (n-type) and hole-doped (p-type) cuprates reveal that the pairing symmetry, pseudogap phenomenon and spatial homogeneity of the superconducting order parameter are all non-universal. We compare ... More
One-dimensional infinite component vector spin glass with long-range interactionsMay 17 2012We investigate zero and finite temperature properties of the one-dimensional spin-glass model for vector spins in the limit of an infinite number m of spin components where the interactions decay with a power, \sigma, of the distance. A diluted version ... More
Medium modifications of the nucleon--deuteron break--up cross section in the Faddeev approachJan 25 1996The three--nucleon scattering problem in a nuclear medium is considered within the Faddeev technique. In particular the deuteron break--up cross section that governs the formation and the break--up reactions of deuterons (NNN <-> Nd) in a nuclear environment ... More
Unconventional Low-Energy Excitations of Cuprate SuperconductorsSep 02 2009Recent development in the physics of high-temperature cuprate superconductivity is reviewed, with special emphasis on the phenomena of unconventional and non-universal low-energy excitations of hole- and electron-type cuprate superconductors and the possible ... More
Magnetic structure of the antiferromagnetic half-Heusler compound NdBiPtMar 15 2015Oct 18 2015We present results of single crystal neutron diffraction experiments on the rare-earth, half-Heusler antiferromagnet (AFM) NdBiPt. This compound exhibits an AFM phase transition at $T_{\mathrm N}=2.18$~K with an ordered moment of $1.78(9)$~$\mu_{\mathrm ... More
Femtosecond Quasiparticle and Phonon Dynamics in Superconducting YBa2Cu3O7 Studied by Wideband Terahertz SpectroscopyJun 17 2010Jun 18 2010We measure the anisotropic mid-infrared response of electrons and phonons in bulk YBa2Cu3O7 after femtosecond photoexcitation. A line shape analysis of specific lattice modes reveals their transient occupation and coupling to the superconducting condensate. ... More
Photodisintegration studies on p-nuclei: The case of Mo and Sm isotopesOct 26 2007In explosive stellar environments like supernovae, the temperatures are high enough for the production of heavy neutron-deficient nuclei, the socalled p-nuclei. Up to now, the knowledge of the reaction rates of p-nuclei is based on theoretical parameterizations ... More
B-T phase diagram of CoCr2O4 in magnetic fields up to 14 TNov 30 2011We have measured the magnetization and specific heat of multiferroic CoCr2O4 in magnetic fields up to 14 T. The high-field magnetization measurements indicate a new phase transition at T* = 5 - 6 K. The phase between T* and the lock-in transition at 15 ... More
Photoactivation experiment on 197Au and its implications for the dipole strength in heavy nucleiNov 28 2008The 197Au(gamma,n) reaction is used as an activation standard for photodisintegration studies on astrophysically relevant nuclei. At the bremsstrahlung facility of the superconducting electron accelerator ELBE (Electron Linear accelerator of high Brilliance ... More
Photon strength distributions in stable even-even molybdenum isotopesJul 26 2007Electromagnetic dipole-strength distributions up to the particle separation energies are studied for the stable even-even nuclides $^{92,94,96,98,100}$Mo in photon scattering experiments at the superconducting electron accelerator ELBE of the Forschungszentrum ... More
Photodissociation of p-process nuclei studied by bremsstrahlung induced activationDec 20 2005A research program has been started to study experimentally the near-threshold photodissociation of nuclides in the chain of cosmic heavy element production with bremsstrahlung from the ELBE accelerator. An important prerequisite for such studies is good ... More
Magnetic properties of the quasi-two-dimensional S = 1/2 Heisenberg antiferromagnet [Cu(pyz)2(HF2)]PF6Nov 23 2009We report on high-field magnetization, specific-heat and electron spin resonance (ESR) studies of the quasi-two-dimensional spin-1/2 Heisenberg antiferromagnet [Cu(pyz)2(HF2)]PF6. The frequency-field diagram of ESR modes below TN = 4.38 K is described ... More
Ultrafast transient generation of spin-densitywave order in the normal state of BaFe2As2 driven by coherent lattice vibrationsJul 17 2012The interplay among charge, spin and lattice degrees of freedom in solids gives rise to intriguing macroscopic quantum phenomena such as colossal magnetoresistance, multiferroicity and high-temperature superconductivity. Strong coupling or competition ... More
Evidence for Strain-Induced Local Conductance Modulations in Single-Layer Graphene on SiO2Mar 13 2009Graphene has emerged as an electronic material that is promising for device applications and for studying two-dimensional electron gases with relativistic dispersion near two Dirac points. Nonetheless, deviations from Dirac-like spectroscopy have been ... More
Weak Decays of Heavy Mesons in the Instantaneous Bethe Salpeter ApproachDec 22 1994In the framework of the instantaneous Bethe Salpeter equation we investigate weak decays of B and D mesons. Mesons are described as q-bar q states interacting via a mixture of a scalar and a vector confining kernel and a one gluon exchange. The model ... More
Quasiparticle spectroscopy and high-field phase diagrams of cuprate superconductors -- An investigation of competing orders and quantum criticalityAug 04 2004We present scanning tunneling spectroscopic and high-field thermodynamic studies of hole- and electron-doped (p- and n-type) cuprate superconductors. Our experimental results are consistent with the notion that the ground state of cuprates is in proximity ... More
Dimensionality of superconductivity in the infinite-layer high-temperature cuprate Sr0.9M0.1CuO2 (M = La, Gd)May 04 2004The high magnetic field phase diagram of the electron-doped infinite layer high-temperature superconducting (high-T_c) compound Sr_{0.9}La_{0.1}CuO_2 was probed by means of penetration depth and magnetization measurements in pulsed fields to 60 T. An ... More
Light clusters in nuclear matter of finite temperatureOct 22 2003We investigate properties and the distribution of light nuclei (A<4) in symmetric nuclear matter of finite temperature within a microscopic framework. For this purpose we have solved few-body Alt-Grassberger-Sandhas type equations for quasi-nucleons that ... More
Few-Body States in Fermi-Systems and Condensation PhenomenaNov 02 1999Residual interactions in many particle systems lead to strong correlations. A multitude of spectacular phenomenae in many particle systems are connected to correlation effects in such systems, e.g. pairing, superconductivity, superfluidity, Bose-Einstein ... More
Light Nuclei within Nuclear MatterMar 17 2005We investigate the properties of 3He, 4He, 6He, 7Li and 16O nuclei in nuclear matter of finite temperature and density. A Dyson expansion of the many-body Green function leads to few-body equations that are solved using the ntegro-Differential Equation ... More
Competing Orders and Quantum Phase Fluctuations on the Low-Energy Excitations and Pseudogap Phenomena of Cuprate SuperconductorsJun 09 2006Oct 10 2007We investigate the low-energy quasiparticle excitation spectra of cuprate superconductors by incorporating both superconductivity (SC) and competing orders (CO) in the bare Green's function and quantum phase fluctuations in the proper self-energy. Our ... More
Conditional Model CheckingSep 30 2011Software model checking, as an undecidable problem, has three possible outcomes: (1) the program satisfies the specification, (2) the program does not satisfy the specification, and (3) the model checker fails. The third outcome usually manifests itself ... More
Experimental Investigation of the Competing Orders and Quantum Criticality in Hole- and Electron-Doped Cuprate SuperconductorsAug 04 2004We investigate the issues of competing orders and quantum criticality in cuprate superconductors via experimental studies of the high-field thermodynamic phase diagrams and the quasiparticle tunneling spectroscopy. Our results suggest substantial field-induced ... More
Torsional Oscillations of Slowly Rotating Relativistic StarsMar 06 2007We study the effects of rotation on the torsional modes of oscillating relativistic stars with a solid crust. Earlier works in Newtonian theory provided estimates of the rotational corrections for the torsional modes and suggested that they should become ... More
A Timing RPC with low resistive ceramic electrodesJun 07 2018For precise start time determination a Beam Fragmentation T$_0$ Counter (BFTC) is under development for the Time-of-Flight Wall of the Compressed Baryonic Matter Spectrometer (CBM) at the Facility for Antiproton and Ion Research (FAIR) at Darmstadt/Germany. ... More
Formation of Few-Body Clusters in Nuclear MatterMay 12 2000Starting from a suitably modified three-body equation to include dominant medium effects such as self energy corrections and Pauli blocking I present results on several observables relevant for the formation of light clusters in a heavy ion collision ... More
Trawling for transits in a sea of noise: A Search for Exoplanets by Analysis of WASP Optical Lightcurves and Follow-up (SEAWOLF)Oct 28 2013Nov 20 2013Studies of transiting Neptune-size planets orbiting close to nearby bright stars can inform theories of planet formation because mass and radius and therefore mean density can be accurately estimated and compared with interior models. The distribution ... More
Global Albedos of Pluto and Charon from LORRI New Horizons ObservationsApr 20 2016The exploration of the Pluto-Charon system by the New Horizons spacecraft represent the first opportunity to understand the distribution of albedo and other photometric properties of the surfaces of objects in the Solar System's "Third Zone" within the ... More
Pressure dependent relaxation in the photo-excited Mott insulator ETF2TCNQ: Influence of hopping and correlations on quasiparticle recombination ratesAug 09 2013Feb 23 2015Femtosecond relaxation of photo-excited quasiparticles in the one dimensional Mott insulator ET-F2TCNQ are measured as a function of external pressure, which is used to tune the electronic structure. By fitting the static optical properties and measuring ... More
Pygmy dipole strength in 90ZrNov 27 2008The dipole response of the N=50 nucleus 90Zr was studied in photon-scattering experiments at the electron linear accelerator ELBE with bremsstrahlung produced at kinetic electron energies of 7.9, 9.0, and 13.2 MeV. We identified 189 levels up to an excitation ... More
Few nucleon dynamics in a nuclear mediumSep 01 1998Few body methods are used in many particle physics to describe correlations, bound states, and reactions in strongly correlated quantum systems. Although this has already been recognized earlier, rigorous attempts to treat three-body collisions have only ... More
Model Analysis of Time Reversal Symmetry Test in the Caltech Fe-57 Gamma-Transition ExperimentApr 13 1993The CALTECH gamma-transition experiment testing time reversal symmetry via the E2/M1 mulipole mixing ratio of the 122 keV gamma-line in Fe-57 has already been performed in 1977. Extending an earlier analysis in terms of an effective one-body potential, ... More
Three- and Four-body correlations in nuclear matterOct 17 2001Few-nucleon correlations in nuclear matter at finite densities and temperatures are explored. Using the Dyson equation approach leads to effective few-body equations that include self energy corrections and Pauli blocking factors in a systematic way. ... More
Linear Perturbations in a coupled cosmon-bolon cosmologyJul 02 2014We investigate linear perturbations in the recently proposed cosmon-bolon model of coupled scalar field dark matter and quintessence. We provide an analytical mechanism to average over the quick oscillations appearing both in the background and at the ... More
Test of Time Reversal Invariance in Proton Deuteron SystemFeb 03 1993Internal target experiments with high quality proton beams allow for a new class of experiments providing null tests of time reversal symmetry in forward scattering. This could yield more stringent limits on T-odd P-even observables. A excellent candidate ... More
Adiabatic perturbations in coupled scalar field cosmologiesJul 01 2014We present a comprehensive and gauge invariant treatment of perturbations around cosmological scaling solutions for two canonical scalar fields coupled through a common potential in the early universe, in the presence of neutrinos, photons and baryons, ... More
Light front field theory of quark matter at finite temperatureOct 29 2003A light front field theory for finite temperature and density is currently being developed. It will be used here to describe the transition region from quark matter to nuclear matter relevant in heavy ion collisions and in the early universe. The energy ... More
Clusters and condensates in Fermi systemsOct 24 2002Superconductivity, superfluidity, condensation, cluster formation, etc. are phenomena that might occur in many-particle systems. These are due to residual interactions between the particles. To explain these phenomena consistently in a microscopic approach, ... More
Few-body correlations in the QCD phase diagramOct 01 2002From the viewpoint of statistical physics, nuclear matter is a strongly correlated many-particle system. Several regimes of the QCD phase diagram should exhibit strong correlations. Here I focus on three- and four-body correlations that might be important ... More
Determination of V_cb from exclusive decays in a relativistic quark modelDec 22 1997In the framework of a relativistic covariant Bethe-Salpeter model for the quark-antiquark system we present a renewed determination of the Cabbibo-Kobayashi-Maskawa matrix element $|V_{cb}|$. Complementing an earlier analysis applied to the whole decay ... More
Few-Body Correlations in Fermi SystemsDec 23 2000I present recent results on few-body correlations in nuclear matter at finite temperatures and densities. In particular I focus on the four-body correlations. The alpha-particle is the strongest bound state. The investigation is done based on effective ... More
Effective T-odd P-even hadronic interactions from quark modelsMay 13 1996Tests of time reversal symmetry at low and medium energies may be analyzed in the framework of effective hadronic interactions. Here, we consider the quark structure of hadrons to make a connection to the more fundamental degrees of freedom. It turns ... More
Light-front field theory of hot and dense quark matterOct 01 2004Extending the concepts of light-front field theory to quantum statistics provides a novel approach towards nuclear matter under extreme conditions. Such conditions exist, e.g., in neutron stars or in the early stage of our universe. They are experimentally ... More
A Near-Infrared 64-pixel Superconducting Nanowire Single Photon Detector Array with Integrated Multiplexed ReadoutApr 10 2015We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce ... More
Relativistic Quark Spin Coupling Effects in the Nucleon Electromagnetic Form FactorsNov 03 1999We investigate the effect of different forms of relativistic spin coupling of constituent quarks in the nucleon electromagnetic form factors. The four-dimensional integrations in the two-loop Feynman diagram are reduced to the null-plane, such that the ... More
Q value and half-life of double-electron capture in Os-184Sep 24 2012Os-184 has been excluded as a promising candidate for the search of neutrinoless double-electron capture. High-precision mass measurements with the Penning-trap mass spectrometer TRIGA-TRAP resulted in a marginal resonant enhancement with = -8.89(58) ... More
Convective radial energy flux due to resonant magnetic perturbations and magnetic curvature at the tokamak plasma edgeMay 02 2014With the resonant magnetic perturbations (RMPs) consolidating as an important tool to control the transport barrier relaxation, the mechanism on how they work is still a subject to be clearly understood. In this work we investigate the equilibrium states ... More
Relativistic Quark Spin Coupling Effects in the Correlations Between Nucleon Electroweak PropertiesJul 24 2000Mar 06 2001We investigate the effect of different relativistic spin couplings of constituent quarks on nucleon electroweak properties. Within each quark spin coupling scheme the correlations between static electroweak observables are found to be independent of the ... More
Feynman versus Bakamjian-Thomas in Light Front DynamicsApr 12 1999We compare the Bakamjian-Thomas (BT) formulation of relativistic few-body systems with light front field theories that maintain closer contact with Feynman diagrams. We find that Feynman diagrams distinguish Melosh rotations and other kinematical quantities ... More
Neutron Charge Radius: Relativistic Effects and the Foldy TermMay 12 2003The neutron charge radius is studied within a light-front model with different spin coupling schemes and wave functions. The cancellation of the contributions from the Foldy term and Dirac form factor to the neutron charge form factor is verified for ... More
Rotating magnetic field driven spin-up flow in a rectangular cavityDec 06 2016This study presents numerical simulations and experiments considering the flow of an electrically conducting fluid inside a cube driven by a rotating magnetic field (RMF). The investigations are focused on the spin-up, where a liquid metal (GaInSn) is ... More
The alpha-particle in nuclear matterMar 30 2000May 11 2000Among the light nuclear clusters the alpha-particle is by far the strongest bound system and therefore expected to play a significant role in the dynamics of nuclei and the phases of nuclear matter. To systematically study the properties of the alpha-particle ... More
Dynamics of few-body states in a mediumOct 02 2004Strongly interacting matter such as nuclear or quark matter leads to few-body bound states and correlations of the constituents. As a consequence quantum chromodynamics has a rich phase structure with spontaneous symmetry breaking, superconductivity, ... More
Investigating the Physical Origin of Unconventional Low-Energy Excitations and Pseudogap Phenomena in Cuprate SuperconductorsSep 15 2006We investigate the physical origin of unconventional low-energy excitations in cuprate superconductors by considering the effect of coexisting competing orders (CO) and superconductivity (SC) and of quantum fluctuations and other bosonic modes on the ... More
Dynamics of photoinduced Charge Density Wave-metal phase transition in K0.3MoO3Jan 14 2009We present first systematic studies of the photoinduced phase transition from the ground charge density wave (CDW) state to the normal metallic (M) state in the prototype quasi-1D CDW system K0.3MoO3. Ultrafast non-thermal CDW melting is achieved at the ... More
Second-harmonic generation as probe for structural and electronic properties of buried GaP/Si(001) interfacesNov 04 2016Optical second-harmonic generation is demonstrated to be a sensitive probe of the buried interface between the lattice matched semiconductors gallium phosphide and silicon with (001) orientation. Rotational anisotropy measurements of SHG from GaP/Si show ... More
Competing orders and the doping and momentum dependent quasiparticle excitations in cuprate superconductorsOct 31 2006Jan 24 2008The low-energy quasiparticle excitations in hole- and electron-type cuprate superconductors are investigated via both experimental and theoretical means. It is found that the doping and momentum dependence of the empirical low-energy quasiparticle excitations ... More
Observation of vortices and hidden pseudogap from scanning tunneling spectroscopic studies of electron-doped cuprate superconductor $Sr_{0.9}La_{0.1}CuO_2$Sep 03 2008Dec 02 2008We present the first demonstration of vortices in an electron-type cuprate superconductor, the highest $T_c$ (= 43 K) electron-type cuprate $Sr_{0.9}La_{0.1}CuO_2$. Our spatially resolved quasiparticle tunneling spectra reveal a hidden low-energy pseudogap ... More
Comparative studies of the scanning tunneling spectra in cuprate and iron-arsenide superconductorsJul 04 2011We report scanning tunneling spectroscopic studies of cuprate and iron-arsenic superconductors, including YBa_2Cu_3O_{7-\delta} (Y-123, T_c = 93 K), Sr_{0.9}La_{0.1}CuO_2 (La-112, T_c = 43 K), and the "122" compounds Ba(Fe_{1-x}Co_x)_2As_2 (Co-122 with ... More
Macroscopic coherence effects in a mesoscopic system: Weak localization of thin silver films in an undergraduate labMar 09 2005Jun 01 2005We present an undergraduate lab that investigates weak localization in thin silver films. The films prepared in our lab have thickness, $a$, between 60-200 \AA, a mesoscopic length scale. At low temperatures, the inelastic dephasing length for electrons, ... More
Scanning tunneling spectroscopic evidence for magnetic field-induced microscopic orders in the high-$T_c$ superconductor YBa$_2$Cu$_3$O$_{7-δ}$Aug 22 2008Jul 23 2009We report spatially resolved tunneling spectroscopic evidence for field-induced microscopic orders in a high-$T_c$ superconductor $\rm YBa_2Cu_3O_{7-\delta}$. The spectral characteristics inside vortices reveal a pseudogap ($V_{\rm CO}$) larger than the ... More
Modeling glacial flow on and onto Pluto's Sputnik PlanitiaJun 18 2016Jul 26 2018Observations of Pluto's surface made by the New Horizons spacecraft indicates present-day nitrogen ice glaciation in and around the basin known as Sputnik Planum. Motivated by these observations, we have developed an evolutionary glacial flow model of ... More
Global Albedos of Pluto and Charon from LORRI New Horizons ObservationsApr 20 2016Jan 09 2017The exploration of the Pluto-Charon system by the New Horizons spacecraft represents the first opportunity to understand the distribution of albedo and other photometric properties of the surfaces of objects in the Solar System's "Third Zone" of distant ... More
Modeling glacial flow on and onto Pluto's Sputnik PlanumJun 18 2016Observations of Pluto's surface made by the New Horizons spacecraft indicates present-day nitrogen ice glaciation in and around the basin known as Sputnik Planum. Motivated by these observations, we have developed an evolutionary glacial flow model of ... More
A Search for Temporal Changes on Pluto and CharonNov 07 2017A search for temporal changes on Pluto and Charon was motivated by (1) the discovery of young surfaces in the Pluto system that imply ongoing or recent geologic activity, (2) the detection of active plumes on Triton during the Voyager 2 flyby, and (3) ... More
Nonuniqueness of Representations of Wave Equations in Lorentzian Space-TimesNov 19 2012This brief note wants to bring to attention that the formulation of physically reasonable initial-boundary value problems for wave equations in Lorentzian space-times is not unique, i.e., that there are inequivalent such formulations that lead to a different ... More
Observation and calculation of the quasi-bound rovibrational levels of the electronic ground state of H$_2^+$Jan 13 2017Although the existence of quasi-bound rotational levels of the $X^+ \ ^2\Sigma_g^+$ ground state of H$_2^+$ has been predicted a long time ago, these states have never been observed. Calculated positions and widths of quasi-bound rotational levels located ... More
Smooth Gowdy symmetric generalized Taub-NUT solutionsJun 13 2011Jul 19 2012We study a class of S3 Gowdy vacuum models with a regular past Cauchy horizon which we call smooth Gowdy symmetric generalized Taub-NUT solutions. In particular, we prove existence of such solutions by formulating a singular initial value problem with ... More
Light front QED$_{1+1}$ at finite temperatureMay 20 2008We investigate thermodynamic properties of quantum electrodynamics in 1+1 dimensions (QED$_{1+1}$) utilizing light front dynamics. Therefore we derive the partition function of the canonical ensemble in discrete light cone quantization, and calculate ... More
Form factors of exclusive $b\to u$ transitionsJul 02 1998We present the form factors of the $B\to\pi,\rho$ transitions induced by the $b\to u$ quark currents at all kinematically accessible $q^2$. Our analysis is based on the spectral representations of the form factors within the constituent quark picture: ... More
CrocoPat 2.1 Introduction and Reference ManualSep 07 2004CrocoPat is an efficient, powerful and easy-to-use tool for manipulating relations of arbitrary arity, including directed graphs. This manual provides an introduction to and a reference for CrocoPat and its programming language RML. It includes several ... More
Pionic coupling constants of heavy mesons in the quark modelJan 10 1999We analyse pionic couplings of heavy mesons combining PCAC with the dispersion quark model to calculate the relevant transition form factors. Ground states and radial excitations are considered. For the ground state coupling constants the values $\hat ... More
On the well posedness of the Baumgarte-Shapiro-Shibata-Nakamura formulation of Einstein's field equationsJun 01 2004We give a well posed initial value formulation of the Baumgarte-Shapiro-Shibata-Nakamura form of Einstein's equations with gauge conditions given by a Bona-Masso like slicing condition for the lapse and a frozen shift. This is achieved by introducing ... More
Small scale structures in coupled scalar field dark matterJul 01 2014We investigate structure formation for ultralight scalar field dark matter coupled to quintessence, in particular the cosmon-bolon system. The linear power spectrum is computed by a numerical solution of the coupled field equations. We infer the substructure ... More
Streaming Data from HDD to GPUs for Sustained Peak PerformanceFeb 18 2013In the context of the genome-wide association studies (GWAS), one has to solve long sequences of generalized least-squares problems; such a task has two limiting factors: execution time --often in the range of days or weeks-- and data management --data ... More
Strong Steiner Tree Approximations in PracticeSep 29 2014Dec 09 2015In this experimental study we consider Steiner tree approximations that guarantee a constant approximation of ratio smaller than $2$. The considered greedy algorithms and approaches based on linear programming involve the incorporation of $k$-restricted ... More
An exact smooth Gowdy-symmetric generalized Taub-NUT solutionJan 05 2014Apr 16 2014In a recent paper (Beyer and Hennig, 2012 [9]), we have introduced a class of inhomogeneous cosmological models: the smooth Gowdy-symmetric generalized Taub-NUT solutions. Here we derive a three-parametric family of exact solutions within this class, ... More
Structure and dynamics of H$_2^+$ near the dissociation threshold: a combined experimental and computational investigationJun 16 2016The pulsed-field-ionization zero-kinetic-energy photoelectron spectrum of H$_2$ has been recorded in the vicinity of the dissociative-ionization threshold following three-photon excitation via selected rotational levels of the B $^1\Sigma_u^+$ ($v=19$) ... More
Minimizing the CDF Path Length: A Novel Perspective on Uniformity and Uncertainty of Bounded DistributionsAug 05 2015Jun 01 2016An index of uniformity is developed as an alternative to the maximum-entropy principle for selecting continuous, differentiable probability distributions $\mathcal{P}$ subject to constraints $C$. The uniformity index developed in this paper is motivated ... More