Results for "G. van Straaten"

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Adsorption induced pyramidal distortion of the tri-metallic nitride core inside the endohedral fullerene Sc$_3$N@C$_{80}$ on the Ag(111) surfaceMar 13 2019Our ability to understand and tailor metal-organic interfaces is mandatory to functionalize organic complexes for next generation electronic and spintronic devices. For magnetic data storage applications, metal-carrying organic molecules, so called single ... More
The aperiodic timing behaviour of the accretion-driven millisecond pulsar SAX J1808.4-3658Sep 12 2003We studied the aperiodic X-ray timing behaviour of the accreting millisecond pulsar SAX J1808.4-3658. The source was recently found to be the first accreting millisecond pulsar that shows the kilohertz quasi-periodic oscillations (kilohertz QPOs) that ... More
The atoll source states of 4U 1608-52Jul 02 2003We have studied the atoll source 4U 1608-52 using a large data set obtained with the Rossi X-ray Timing Explorer. We find that the timing properties of 4U 1608-52 are almost exactly identical to those of the atoll sources 4U 0614+09 and 4U 1728-34 despite ... More
Timing properties and spectral states in Aquila X-1Nov 12 2003We have analyzed five X-ray outbursts of the neutron-star soft X-ray transient Aql X-1 and investigated the timing properties of the source in correlation with its spectral states as defined by different positions in the color-color and hardness-intensity ... More
Relations Between Timing Features and Colors in Accreting Millisecond PulsarsOct 21 2004We have studied the aperiodic X-ray timing and color behavior of the accreting millisecond pulsars SAX J1808.4-3658, XTE J1751-305, XTE J0929-314, and XTE J1814-338 using large data sets obtained with the Rossi X-ray Timing Explorer. We find that the ... More
The atoll source 4U 1608-52 is not a Z sourceJul 30 2002We have studied the spectral and timing behaviour of the atoll source 4U 1608-52. We find that the timing behaviour of 4U 1608-52 is almost identical to that of the atoll sources 4U 0614+09 and 4U 1728-34. Recently Muno, Remillard & Chakrabarty (2002) ... More
A multi-Lorentzian timing study of the atoll sources 4U 0614+09 and 4U 1728-34Jul 30 2001Dec 04 2001We present the results of a multi-Lorentzian fit to the power spectra of two kilohertz QPO sources; 4U 0614+09 and 4U 1728-34. This work was triggered by recent results of a similar fit to the black-hole candidates (BHCs) GX 339-4 and Cyg X-1 by Nowak ... More
Relations Between Timing Features and Colors in the X-Ray Binary 4U 0614+09Jan 27 2000We study the correlations between timing and X-ray spectral properties in the low mass X-ray binary 4U 0614+09 using a large (265-ks) data set obtained with the Rossi X-ray Timing Explorer. We find strong quasi-periodic oscillations (QPOs) of the X-ray ... More
RXTE observations of the dipping low-mass X-ray binary 4U 1624-49Feb 26 2005Apr 04 2005We analyse ~ 360 ks of archival data from the Rossi X-Ray Timing Explorer (RXTE) of the 21 hr orbital period dipping low-mass X-ray binary 4U 1624-49. We find that outside the dips the tracks in the colour-colour and hardness-intensity diagrams (CDs and ... More
An Atlas of Burst Oscillations and Spectral Properties in 4U 1728-34Sep 13 2000Dec 19 2000We study correlations between the burst properties and the position in the color-color diagram of the low mass X-ray binary 4U 1728-34 using 21 bursts found in two data sets obtained with the Rossi X-ray Timing Explorer. Using spectral fits we analyze ... More
X-ray spectral and timing properties of the 2001 superburst of 4U 1636-536Feb 03 2004Preliminary results are reported on the spectral and timing properties of the spectacular 2001 superburst of 4U 1636-536 as seen by the RXTE/PCA. The (broad-band) power-spectral and hardness properties during the superburst are compared to those just ... More
Longitudinal spin Seebeck effect contribution in transverse spin Seebeck effect experiments in Pt/YIG and Pt/NFONov 25 2014We investigate the inverse spin Hall voltage of a 10nm thin Pt strip deposited on the magnetic insulators Y3Fe5O12 (YIG) and NiFe2O4 (NFO) with a temperature gradient in the film plane. We observe characteristics typical of the spin Seebeck effect, although ... More
How unusual was autumn 2006 in Europe?Nov 23 2007The temperatures in large parts of Europe have been record high during the meteorological autumn of 2006. Compared to 1961-1990, the 2m temperature was more than three degrees Celsius above normal from the North side of the Alps to southern Norway. This ... More
Observing Cluster Galaxies and their Progenitors with JDEMAug 04 2004The Joint Dark Energy Mission (JDEM) is expected to have a field-of-view that is several orders of magnitude larger than that of current instruments on the Hubble Space Telescope, with only slightly reduced sensitivity and resolution. This contribution ... More
Predicting Stellar Angular SizesApr 21 1999Jan 31 2001Reliable prediction of stellar diameters, particularly angular diameters, is a useful and necessary tool for the increasing number of milliarcsecond resolution studies being carried out in the astronomical community. A new and accurate technique of predicting ... More
Downstream asymptotics in exterior domains: from stationary wakes to time periodic flowsNov 04 2004We consider the time-dependent Navier-Stokes equations in a half-space with boundary data on the line $(x,y)=(x_0,y)$ assumed to be time-periodic (or stationary) with a fixed asymptotic velocity ${\bf u}_{\infty}=(1,0)$ at infinity. We show that there ... More
The Recent and Continuing Assembly of Field Ellipticals by Red MergersJun 27 2005Sep 01 2005We present a study of tidal debris associated with 126 nearby red galaxies selected from the MUSYC and NDWFS surveys. In the full sample 67 galaxies (53%) show morphological signatures of tidal interactions, consisting of broad fans of stars, tails, and ... More
Soft Physics in STARNov 19 2002Nov 26 2002The STAR Experiment at RHIC is well-suited to making measurements of particle yields from relativistic nuclear collisions in the low transverse momentum, or "soft", regime. We present preliminary results on measurements of pion (0,-,+), kaon (-,+,0short), ... More
Formation and Evolution of Galaxies in ClustersDec 26 2001Elliptical and S0 galaxies dominate the galaxy population in nearby rich clusters such as Coma. Studies of the evolution of the colors, M/L ratios, and line indices of early-type galaxies indicate that they have been a highly homogeneous, slowly evolving ... More
Closure Phase Signatures of Planet Transit EventsApr 16 2008Planet transit events present as attractive targets for the ultra-high-resolution capabilities afforded by optical interferometers. Herein is presented an evaluation of the possibility of detection of such events through measurement of high-precision ... More
Cosmic-Ray Rejection by Laplacian Edge DetectionAug 01 2001Conventional algorithms for rejecting cosmic-rays in single CCD exposures rely on the contrast between cosmic-rays and their surroundings, and may produce erroneous results if the Point Spread Function (PSF) is smaller than the largest cosmic-rays. This ... More
Identification of multidisciplinary research based upon dissimilarity analysis of journals included in reference lists of Wageningen University & Research articlesJul 23 2018Oct 01 2018This paper discusses the identification of journal articles that probably report on multidisciplinary research. Identification of these articles may be important for strategic purposes for the institution where the research is performed or for the evaluation ... More
Transformations of real-time finite-temperature Feynman rulesJun 02 1994We consider transformations of the $2\times2$ propagator matrix in real-time finite-temperature field theory, resulting in transformed $n$--point functions. As special cases of such a transformation we examine the Keldysh basis, the retarded/advanced ... More
Dynamical Models of Elliptical Galaxies in z=0.5 Clusters: I. Data-Model Comparison and Evolution of Galaxy RotationNov 17 2006We present spatially resolved stellar rotation velocity and velocity dispersion profiles form Keck/LRIS absorption-line spectra for 25 galaxies, mostly visually classified ellipticals, in three clusters at z=0.5. We interpret the kinematical data and ... More
Jammed frictionless discs: connecting local and global responseNov 04 2009By calculating the linear response of packings of soft frictionless discs to quasistatic external perturbations, we investigate the critical scaling behavior of their elastic properties and non-affine deformations as a function of the distance to jamming. ... More
The Fundamental Plane and the evolution of the M/L ratio of early-type field galaxies up to z~1Nov 26 2002Jun 05 2003We analyse the Fundamental Plane (FP) of 26 strong gravitational lens galaxies with redshifts up to z~1, using tabulated data from Kochanek et al. (2000) and Rusin et al. (2003). The lens galaxies effectively form a mass-selected sample of early-type ... More
Theoretical understanding of the nuclear incompressibility: where do we stand ?Aug 31 2003Oct 20 2003The status of the theoretical research on the compressional modes of finite nuclei and the incompressibility $K_\infty$ of nuclear matter, is reviewed. It is argued that the recent experimental data on the Isoscalar Giant Monopole Resonance (ISGMR) allow ... More
Wick Theorem for General Initial StatesFeb 23 2011Mar 28 2012We present a compact and simplified proof of a generalized Wick theorem to calculate the Green's function of bosonic and fermionic systems in an arbitrary initial state. It is shown that the decomposition of the non-interacting $n$-particle Green's function ... More
Drinfeld modular curve and Weil pairingNov 22 2004In this paper we describe the compactification of the Drinfeld modular curve. This compactification is analogous to the compactification of the classical modular curve given by Katz and Mazur. We show how the Weil pairing on Drinfeld modules that we defined ... More
Dynamical Models of Elliptical Galaxies in z=0.5 Clusters: II. Mass-to-Light Ratio Evolution without Fundamental Plane AssumptionsNov 17 2006We study M/L evolution of early-type galaxies using dynamical modeling of resolved internal kinematics. This makes fewer assumptions than Fundamental Plane (FP) studies and provides a powerful new approach for studying galaxy evolution. We focus on the ... More
Hubble Space Telescope Images of Red Mergers: How Dry are They?Feb 19 2008Mergers between red galaxies are observed to be common in the nearby Universe, and are thought to be the dominant mechanism by which massive galaxies grow their mass at late times. These ``dry'' mergers can be readily identified in very deep ground based ... More
The Fundamental Plane at z=1.27: First Calibration of the Mass Scale of Red Galaxies at Redshifts z>1Oct 29 2002We present results on the Fundamental Plane (FP) of early-type galaxies in the cluster RDCS J0848+4453 at z=1.27. Internal velocity dispersions of three K-selected early-type galaxies are determined from deep Keck spectra. Structural parameters are determined ... More
Deciding $k$CFA is complete for EXPTIMENov 22 2013We give an exact characterization of the computational complexity of the $k$CFA hierarchy. For any $k > 0$, we prove that the control flow decision problem is complete for deterministic exponential time. This theorem validates empirical observations that ... More
Bound States in the LFD Yukawa ModelJul 28 2004Our purpose is to calculate relativistic bound states in a quantum filed theoretical approach. We work in the Yukawa model and first calculate the bound-state equation in the ladder approximation. We discuss why this is not a complete treatment and what ... More
Oscillator model for dissipative QED in an inhomogeneous dielectricSep 24 2004The Ullersma model for the damped harmonic oscillator is coupled to the quantised electromagnetic field. All material parameters and interaction strengths are allowed to depend on position. The ensuing Hamiltonian is expressed in terms of canonical fields, ... More
Modified atomic decay rate near absorptive scatterers at finite temperatureJul 03 2015The change in the decay rate of an excited atom that is brought about by extinction and thermal-radiation effects in a nearby dielectric medium is determined from a quantummechanical model. The medium is a collection of randomly distributed thermally-excited ... More
Stationary State Fluctuation Theorems for Driven Langevin SystemsJan 27 2007Recent results on the stationary state Fluctuation Theorems for work and heat fluctuations of Langevin systems are presented. The relevance of finite time corrections in understanding experimental and simulation results is explained in the context of ... More
Stationary and Transient Work-Fluctuation Theorems for a Dragged Brownian ParticleDec 12 2002Recently Wang et al. carried out a laboratory experiment, where a Brownian particle was dragged through a fluid by a harmonic force with constant velocity of its center. This experiment confirmed a theoretically predicted work related integrated (I) Transient ... More
Non-equilibrium Thermodynamics and FluctuationsOct 11 2003Nov 05 2003In the last ten years, a number of ``Conventional Fluctuation Theorems'' have been derived for systems with deterministic or stochastic dynamics, in a transient or in a non-equilibrium stationary state. These theorems gave explicit expressions for the ... More
Theory of the Transient and Stationary Fluctuation Theorems for a Dragged Brownian Particle in a FluidOct 22 2002Comment on ``Experimental Demonstration of Violations of the Second Law of Thermodynamics for Small Systems and Short Time Scales''
Elaborating Transition Interface Sampling MethodsMay 06 2004We review two recently developed efficient methods for calculating rate constants of processes dominated by rare events in high-dimensional complex systems. The first is transition interface sampling (TIS), based on the measurement of effective fluxes ... More
Quantum Measurement Reliability versus ReversibilityJan 07 2009There is a constraining relation between the reliability of a quantum measurement and the extent to which the measurement process is, in principle, reversible. The greater the information that is gained, the less reversible the measurement dynamics become. ... More
Discretization of Linear Problems in Banach Spaces: Residual Minimization, Nonlinear Petrov-Galerkin, and Monotone Mixed MethodsNov 13 2015This work presents a comprehensive optimal-discretization theory for linear equations in Banach spaces. As part of our theory, a class of nonlinear Petrov-Galerkin projectors is studied, which are key in establishing optimal a priori error estimates involving ... More
Relative asymptotics for polynomials orthogonal with respect to a discrete Sobolev inner productMar 15 1994We investigate the asymptotic properties of orthogonal polynomials for a class of inner products including the discrete Sobolev inner products $\langle h,g \rangle = \int hg\, d\mu + \sum_{j=1}^m \sum_{i=0}^{N_j} M_{j,i} h^{(i)}(c_j) g^{(i)}(c_j)$, where ... More
On the Precise Determination of the Fermi Coupling Constant from the Muon LifetimeApr 06 1999The determination of the Fermi coupling constant, G_F, is examined in the light of recently calculated 2-loop QED corrections and planned experiments to measure the muon lifetime to a level below 1ppm. The methods used in the calculation of the QED corrections ... More
HAYSTAC Status, Results, and PlansJan 07 2019Jan 13 2019We describe the design of the dark matter experiment Haloscope At Yale Sensitive To Axion Cold Dark Matter (HAYSTAC), and report the results of a haloscope search for dark matter axions. We exclude axion models with axion-photon couplings $g_{a\gamma\gamma} ... More
Magnetic monopole field exposed by electronsMay 02 2013Jun 20 2014Magnetic monopoles have provided a rich field of study, leading to a wide area of research in particle physics, solid state physics, ultra-cold gases, superconductors, cosmology, and gauge theory. So far, no true magnetic monopoles were found experimentally. ... More
Worst-case multi-objective error estimation and adaptivityApr 15 2016This paper introduces a new computational methodology for determining a-posteriori multi-objective error estimates for finite-element approximations, and for constructing corresponding (quasi-)optimal adaptive refinements of finite-element spaces. As ... More
Extended Heat-Fluctuation Theorems for a System with Deterministic and Stochastic ForcesNov 14 2003Nov 26 2003Heat fluctuations over a time \tau in a non-equilibrium stationary state and in a transient state are studied for a simple system with deterministic and stochastic components: a Brownian particle dragged through a fluid by a harmonic potential which is ... More
Challenges in calculations for multi-particle processesOct 13 2004The physics of high-energy collider experiments asks for delicate comparisons between theoretical predictions and experimental data. Signals and potential backgrounds for new physics have to be predicted at sufficient accuracy. The accuracy as well as ... More
On the Assembly History of Early-Type Galaxies in the Hubble Deep Field NorthJun 23 2003We present deep Keck spectroscopy for a sample of I<22.5 field early-type galaxies selected morphologically in the redshift range 0.56<z<1.02 in the HDF-N. Using velocity dispersions determined from the Keck spectra in conjunction with structural parameters ... More
Automating First-Principles Phase Diagram CalculationsJan 28 2002Jun 02 2004Devising a computational tool that assesses the thermodynamic stability of materials is among the most important steps required to build a ``virtual laboratory'', where materials could be designed from first-principles without relying on experimental ... More
Configuration Structures, Event Structures and Petri NetsDec 20 2009In this paper the correspondence between safe Petri nets and event structures, due to Nielsen, Plotkin and Winskel, is extended to arbitrary nets without self-loops, under the collective token interpretation. To this end we propose a more general form ... More
Is the X(3872) a molecule?Sep 06 2012Because of the controversial X(3872) meson's very close proximity to the $D^0\bar{D}^{*0}$ threshold, this charmonium-like resonance is often considered a meson-meson molecule. However, a molecular wave function must be essentially of a meson-meson type, ... More
Coupled-channel analysis of the X(3872)May 14 2010The X(3872) is studied as an axial-vector charmonium state in the multichannel framework of the Resonance-Spectrum-Expansion quark-meson model, previously applied to a variety of other puzzling mesonic resonances. Included are the open-charm pseudoscalar-vector ... More
Morphological Evolution and the Ages of Early-Type Galaxies in ClustersJan 26 2001Morphological and spectroscopic studies of high redshift clusters indicate that a significant fraction of present-day early-type galaxies was transformed from star forming galaxies at z<1. On the other hand, the slow luminosity evolution of early-type ... More
A JavaScript Passive Evolution CalculatorJan 12 2005We present a JavaScript calculator which provides the redshift evolution of the luminosities and colors of passively evolving galaxies for a range of rest-frame filters. In its simplest form it gives the evolution of a single age stellar population formed ... More
A Massive Disk Galaxy at z=1.34Oct 05 2001We report the discovery of a rapidly rotating disk in a K-selected galaxy at z=1.34. Spatially resolved kinematics are determined from deep, moderate resolution Keck spectroscopy covering the redshifted [OII] 3727 line. A conservative estimate of the ... More
Dust in the Cores of Early-Type GalaxiesJul 25 1995The dust properties of all early-type galaxies imaged with the Planetary Camera of the HST in cycles I-III are examined. Dust is detected in 31 out of 64 galaxies, although the sample is biased against the detection of dust. From the distribution of observed ... More
Ballistic orbits in Schwarzschild space-time and gravitational waves from EMR binary mergersJun 17 2014Oct 28 2014We describe a special class of ballistic geodesics in Schwarzschild space-time, extending to the horizon in the infinite past and future of observer time, which are characterized by the property that they are in 1-1 correspondence, and completely degenerate ... More
Fano diagonalization of a polariton model for an inhomogeneous absorptive dielectricAug 02 2004The Hamiltonian of a polariton model for an inhomogeneous linear absorptive dielectric is diagonalized by means of Fano's diagonalization method. The creation and annihilation operators for the independent normal modes are explicitly found as linear combinations ... More
LiH as a Li$^+$ and H$^-$ ion providerDec 19 2014We present a first-principles study of the formation and migration of native defects in lithium hydride (LiH), a material of interest in hydrogen storage and lithium-ion batteries. We find that the negatively charged lithium vacancy and positively charged ... More
Effective field theories for disordered systems from the logarithmic derivative of the wave-functionSep 07 2001We consider a spinless particle moving in a random potential on a d-dimensional torus. Introducing the gradient of the logarithm of the wave-function transforms the time independent Schroedinger equation into a stochastic differential equation with the ... More
Implementation of a Gauss convoluted Pandel PDF for track reconstruction in Neutrino TelescopesApr 13 2007Sep 05 2007A probability distribution function is presented which provides a realistic description of the detection of scattered photons. The resulting probabilities can be described analytically by means of a superposition of several special functions. These exact ... More
Reducing reflections from mesh refinement interfaces in numerical relativityMay 19 2005Full interpretation of data from gravitational wave observations will require accurate numerical simulations of source systems, particularly binary black hole mergers. A leading approach to improving accuracy in numerical relativity simulations of black ... More
Reeconstructing Sigma0 decays in STAROct 26 2004Typical comparisons of data from nuclear collisions to particle production models require a caveat for (anti)Lambda yields from experimental inability to separate the contributions of those yields from Sigma state decays. Recent analysis in STAR is leading ... More
STAR Strangeness Results from sqrt(s_NN) = 130 GeV Au+Au Collisions (and first results from 200 GeV)Jan 17 2002The STAR Experiment at RHIC is capable of a wide variety of measurements of the production of strange hadrons in nuclear collisions. Measurements of the relative production of strange baryons, antibaryons, and kaons can shed light on the baryon densities ... More
Dirac cones beyond the honeycomb lattice: a symmetry based approachOct 21 2015Jan 11 2016Recently, several new materials exhibiting massless Dirac fermions have been proposed. However, many of these do not have the typical graphene honeycomb lattice, which is often associated with Dirac cones. Here, we present a classification of these different ... More
Force-induced desorption of $3$-star polymers: a self-avoiding walk modelDec 18 2017Mar 22 2018We consider a simple cubic lattice self-avoiding walk model of 3-star polymers adsorbed at a surface and then desorbed by pulling with an externally applied force. We determine rigorously the free energy of the model in terms of properties of a self-avoiding ... More
The Hamiltonian H=xp and classification of osp(1|2) representationsJan 08 2010The quantization of the simple one-dimensional Hamiltonian H=xp is of interest for its mathematical properties rather than for its physical relevance. In fact, the Berry-Keating conjecture speculates that a proper quantization of H=xp could yield a relation ... More
Deep Learning for Semantic Segmentation on Minimal HardwareJul 15 2018Deep learning has revolutionised many fields, but it is still challenging to transfer its success to small mobile robots with minimal hardware. Specifically, some work has been done to this effect in the RoboCup humanoid football domain, but results that ... More
Discretization of Linear Problems in Banach Spaces: Residual Minimization, Nonlinear Petrov-Galerkin, and Monotone Mixed MethodsNov 13 2015Jul 29 2018This work presents a comprehensive discretization theory for abstract linear operator equations in Banach spaces. The fundamental starting point of the theory is the idea of residual minimization in dual norms, and its inexact version using discrete dual ... More
Fixed point-free isometric actions of topological groups on Banach spacesApr 09 2008Nov 06 2008We show that every non-precompact topological group admits a fixed point-free continuous action by affine isometries on a suitable Banach space. Thus, precompact groups are defined by the fixed point property for affine isometric actions on Banach spaces. ... More
The Star Formation Epoch of the Most Massive Early-Type GalaxiesSep 20 2006Nov 30 2006We present new Keck spectroscopy of early-type galaxies in three galaxy clusters at z~0.5. We focus on the fundamental plane (FP) relation, and combine the kinematics with structural parameters determined from HST images. The galaxies obey clear FP relations, ... More
IRAS08281-4850 and IRAS14325-6428: two A-type post-AGB stars with s-process enrichmentJun 14 2007One of the puzzling findings in the study of the chemical evolution of (post-)AGB stars is why very similar stars (in terms of metallicity, spectral type, infrared properties, etc...) show a very different photospheric composition. We aim at extending ... More
Recognition of paper samples by correlation of their speckle patternsOct 12 2006Oct 17 2006Buchanan et al. [Nature 436, p. 475 (2005)] have shown that it is possible to recognize paper samples via their speckle pattern by using a line-shaped laser focus, four photo detectors and a scanning mechanism. In this report recognition of five out of ... More
A model for the formation energies of alanates and boranatesNov 27 2006We develop a simple model for the formation energies (FEs) of alkali and lkaline earth alanates and boranates, based upon ionic bonding between metal cations and (AlH4)- or (BH4)- anions. The FEs agree well with values obtained from first principles calculations ... More
Load-depth sensing of isotropic, linear viscoelastic materials using rigid axisymmetric indentersJun 07 2016An indentation experiment involves five variables: indenter shape, material behavior of the substrate, contact size, applied load and indentation depth. Only three variable are known afterwards, namely, indenter shape, plus load and depth as function ... More
An Extension of the Fluctuation TheoremMay 07 2003Heat fluctuations are studied in a dissipative system with both mechanical and stochastic components for a simple model: a Brownian particle dragged through water by a moving potential. An extended stationary state fluctuation theorem is derived. For ... More
Recursive equations for Majorana currentsJun 03 2009A recursive computation of scattering amplitudes including Majorana fermions requires a consistent definition of the fermion flow, which is introduced by Denner et al. in a diagrammatic setting. A systematic treatment in the off-shell current formalism ... More
On a Stratification of the Moduli of K3 SurfacesOct 12 1999Jan 06 2000In this paper we give a characterization of the height of K3 surfaces in positive characteristic. This enables us to calculate the cycle classes of the loci in families of K3 surfaces where the height is at least h. The formulas for such loci can be seen ... More
Ground State Properties of an Asymmetric Hubbard Model for Unbalanced Ultracold Fermionic Quantum GasesAug 23 2007Feb 12 2008In order to describe unbalanced ultracold fermionic quantum gases on optical lattices in a harmonic trap, we investigate an attractive ($U<0$) asymmetric ($t_\uparrow\neq t_\downarrow$) Hubbard model with a Zeeman-like magnetic field. In view of the model's ... More
Repulsive Casimir forces between solid materials with high refractive index intervening liquidsApr 29 2010In order to explore repulsive Casimir/van der Waals forces between solid materials with liquid as the intervening medium, we analyze dielectric data for a wide range of materials as for example PTFE, polystyrene, silica and more than twenty liquids. Although ... More
Magnetic structure of actinide metalsDec 19 2008In comparison to 3d or 4f metals, magnetism in actinides remains poorly understood due to experimental complications and the exotic behavior of the 5f states. In particular, plutonium metal is most especially vexing. Over the last five decades theories ... More
Hubble Space Telescope WFC3 Grism Spectroscopy and Imaging of a Growing Compact Galaxy at z=1.9Mar 17 2010We present HST/WFC3 grism spectroscopy of the brightest galaxy at z>1.5 in the GOODS-South WFC3 Early Release Science grism pointing, covering the wavelength range 0.9-1.7 micron. The spectrum is of remarkable quality and shows the redshifted Balmer lines ... More
On the height of Calabi-Yau varieties in positive characteristicFeb 03 2003We study invariants of Calabi-Yau varieties in positive characteristic, especially the height of the Artin-Mazur formal group. We illustrate these results by Calabi-Yau varieties of Fermat and Kummer type.
Observations of Disk Galaxy EvolutionMar 04 2002The morphologies of disk galaxies begin to deviate systematically from those of nearby galaxies at surprisingly low redshifts, possibly as low as z=0.3. This corresponds to a time ~3.5 Gyr in the past, which is only one quarter of the present age of the ... More
The Ratio Sigma0/Lambda at RHICDec 13 2005While yields of Sigma0 have been measured in many different colliding systems, no measurements exist in high energy nuclear collisions. It also remains unexplored whether the relative yields of Sigma0 and Lambda change in collisions of heavy ions where ... More
Ultra Low Surface Brightness Imaging with the Dragonfly Telephoto ArrayJan 21 2014We describe the Dragonfly Telephoto Array, a robotic imaging system optimized for the detection of extended ultra low surface brightness structures. The array consists of eight Canon 400mm f/2.8 telephoto lenses coupled to eight science-grade commercial ... More
Metric perturbations produced by eccentric equatorial orbits around a Kerr black holeJun 15 2015Aug 17 2016We present the first numerical calculation of the (local) metric perturbation produced by a small compact object moving on an eccentric equatorial geodesic around a Kerr black hole, accurate to first order in the mass ratio. The procedure starts by first ... More
A first-principles study of the electronic structure and stability of Be(BH4)2Dec 06 2007Alanates and boranates are studied intensively because of their potential use as hydrogen storage materials. In this paper we present a first-principles study of the electronic structure and the energetics of beryllium boranate, Be(BH4)2. From total energy ... More
Role of defects and impurities in doping of GaNSep 25 1996We have calculated formation energies and position of the defect levels for all native defects and for a variety of donor and acceptor impurities employing first-principles total-energy calculations. An analysis of the numerical results gives direct insight ... More
Analytically solvable Hamiltonians for quantum systems with a nearest neighbour interactionFeb 13 2009We consider quantum systems consisting of a linear chain of n harmonic oscillators coupled by a nearest neighbour interaction of the form $-q_r q_{r+1}$ ($q_r$ refers to the position of the $r$th oscillator). In principle, such systems are always numerically ... More
Discovery of an X-ray pulsar in the low-mass X-ray binary 2A 1822-371Apr 22 2001May 10 2001We report the discovery of 0.59 s X-ray pulsations from the low-mass X-ray binary, 5.57 hr dipping and eclipsing ADC source 2A 1822-371. Pulse arrival time analysis indicates a circular orbit with e < 0.03 (95% confidence) and an asini for the neutron ... More
Epicycles and Poincaré Resonances in General RelativityNov 17 2010The method of geodesic deviations provides analytic approximations to geodesics in arbitrary background space-times. As such the method is a useful tool in many practical situations. In this note we point out some subtleties in the application of the ... More
Formal Brauer groups and the moduli of abelian surfacesDec 21 1999Jan 06 2000In this paper we consider the stratification on the moduli space of principally polarized abelian surfaces in characteristic $p>0$ defined by the height of the formal group associated to $H^2(X,O_X)$. We compute the cycle classes of the strata and compare ... More
Non conventional screening of the Coulomb interaction in low dimensional and finite size systemFeb 12 1998We study the screening of the Coulomb interaction in non polar systems by polarizable atoms. We show that in low dimensions and small finite size systems this screening deviates strongly from that conventionally assumed. In fact in one dimension the short ... More
Modified Gravity and the Radiation Dominated EpochOct 08 2012In this paper we consider scalar-tensor theories, allowing for both conformal and disformal couplings to a fluid with a generic equation of state. We derive the effective coupling for both background cosmology and for perturbations in that fluid. As an ... More
FFLO- and Néel States in finite-size SystemsMar 31 2011The general structure of the $s$-wave fermionic superfluid pairing order parameter is discussed for systems in thermal equilibrium. We demonstrate that for finite-size systems with fixed boundary conditions the pairing-amplitude may always be chosen as ... More
Atomic decay near a quantized medium of absorbing scatterersApr 26 2010The decay of an excited atom in the presence of a medium that both scatters and absorbs radiation is studied with the help of a quantum-electrodynamical model. The medium is represented by a half space filled with a randomly distributed set of non-overlapping ... More