Results for "Friedemann Reinhard"

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Nanoscale Sensing and Quantum CoherenceJun 11 2019Small solid state qubits, most prominently single spins in solids, can be remarkable sensors for various physical quantities ranging from magnetic fields to temperature. They package the performance of their bulk semiconductor counterparts into a nanoscale ... More
Holography of Wi-Fi radiationNov 30 2016May 05 2017Wireless data transmission systems such as WiFi or Bluetooth emit coherent light - electromagnetic waves with precisely known amplitude and phase. Propagating in space, this radiation forms a hologram - a two-dimensional wavefront encoding a three-dimensional ... More
Heuristical and numerical considerations for the carbuncle phenomenonJul 02 2015In this study, we investigate the so called carbuncle phenomenon by means of numerical experiments and heuristic considerations. We identify two main sources for the carbuncle: instability of the 1d shock position and low numerical viscosity on shear ... More
Counterpart of the Weyl tensor for Rarita-Schwinger type fieldsDec 12 2016Apr 02 2017In dimensions larger than 3 a modified field strength for Rarita-Schwinger type fields is constructed whose components are not constrained by the field equations. In supergravity theories the result provides a modified (supercovariant) gravitino field ... More
Supersymmetry algebra cohomology II: Primitive elements in 2 and 3 dimensionsApr 17 2010Dec 01 2010The primitive elements of the supersymmetry algebra cohomology as defined in a companion paper are computed exhaustively for standard supersymmetry algebras in dimensions D=2 and D=3, for all signatures (t,D-t) and all numbers N of sets of supersymmetries. ... More
Extended BRST cohomology, consistent deformations and anomalies of four-dimensional supersymmetric gauge theoriesDec 05 2002Mar 25 2003The local cohomology of an extended BRST differential which includes global N=1 supersymmetry and Poincare transformations is completely and explicitly computed in four-dimensional supersymmetric gauge theories with super-Yang-Mills multiplets, chiral ... More
Gauge covariant algebras and local BRST cohomologyNov 24 1997The formulation of the local BRST cohomology on infinite jet bundles and its relation and reduction to gauge covariant algebras are reviewed. As an illustration, we compute the local BRST cohomology for geodesic motion in (pseudo-) Riemannian manifolds ... More
Aspects of supersymmetric BRST cohomologyJan 17 2012The application and extension of well-known BRST cohomological methods to supersymmetric field theories are discussed. The focus is on the emergence and particular features of supersymmetry algebra cohomology in this context. In particular it is discussed ... More
Supersymmetry algebra cohomology I: Definition and general structureNov 11 2009Dec 01 2010The paper concerns standard supersymmetry algebras in diverse dimensions, involving bosonic translational generators and fermionic supersymmetry generators. A cohomology related to these supersymmetry algebras, termed supersymmetry algebra cohomology, ... More
Seiberg-Witten maps and anomalies in noncommutative Yang-Mills theoriesMar 13 2004A BRST-cohomological analysis of Seiberg-Witten maps and results on gauge anomalies in noncommutative Yang-Mills theories with general gauge groups are reviewed.
Lectures on supergravityApr 03 2002Oct 16 2010The text is an essentially self-contained introduction to four-dimensional N=1 supergravity, including its couplings to super Yang-Mills and chiral matter multiplets, for readers with basic knowledge of standard gauge theories and general relativity. ... More
Local BRST cohomology and covarianceApr 04 1996Sep 03 1997The paper provides a framework for a systematic analysis of the local BRST cohomology in a large class of gauge theories. The approach is based on the cohomology of s+d in the jet space of fields and antifields, s and d being the BRST operator and exterior ... More
Anomaly candidates and invariants of D=4, N=1 supergravity theoriesJun 11 1993All anomaly candidates and the form of the most general invariant local action are given for old and new minimal supergravity, including the cases where additional Yang--Mills and chiral matter multiplets are present. Furthermore nonminimal supergravity ... More
On the Proper Setup of the Double Mach Reflection as a Test Case for the Resolution of Gas Dynamics CodesApr 25 2014May 02 2014This note discusses the initial and boundary conditions as well as the size of the computational domain for the double Mach reflection problem when set up as a test for the resolution of an Euler scheme for gas dynamics.
Heuristical and numerical considerations for the carbuncle phenomenonJul 02 2015Mar 06 2017In this study, we investigate the so called carbuncle phenomenon by means of numerical experiments and heuristic considerations. We identify two main sources for the carbuncle: instability of the 1d shock position and low numerical viscosity on shear ... More
Symmetry for a general class of overdetermined elliptic problemsDec 16 2015Let $\Omega $ be a bounded domain in $\mathbb{R} ^N $, and let $u\in C^1 (\overline{\Omega }) $ be a weak solution of the following overdetermined BVP: $-\nabla (g(|\nabla u|)|\nabla u|^{-1} \nabla u )=f(|x|,u)$, $ u>0 $ in $\Omega $ and $u(x)=0, \ |\nabla ... More
Roe-type schemes for shallow water magnetohydrodynamics with hyperbolic divergence cleaningSep 30 2014We discuss Roe-type linearizations for non-conservative shallow water magnetohydrodynamics without and with hyperbolic divergence cleaning.
A note on the carbuncle in shallow water simulationsJun 02 2012An important problem in gas dynamics simulation is to prevent the carbuncle, a breakdown of discrete shock profiles. We show that for high Froude number, this also occurs in shallow water simulations and give numerical evidence that all cures developed ... More
Scanning probe microscopy with chemical contrast by nanoscale nuclear magnetic resonanceJun 12 2014Scanning probe microscopy is one of the most versatile windows into the nanoworld, providing imaging access to a variety of sample properties, depending on the probe employed. Tunneling probes map electronic properties of samples, magnetic and photonic ... More
Quantum Sensing of Weak Radio-Frequency Signals by Pulsed Mollow Absorption SpectroscopyFeb 22 2017Feb 27 2017Quantum sensors, qubits sensitive to external fields, have become powerful detectors for various small acoustic and electromagnetic fields. A major key to their success have been dynamical decoupling protocols which enhance sensitivity to weak oscillating ... More
Optimized Jastrow-Slater wave functions for ground and excited states: Application to the lowest states of etheneMar 19 2004A quantum Monte Carlo method is presented for determining multi-determinantal Jastrow-Slater wave functions for which the energy is stationary with respect to the simultaneous optimization of orbitals and configuration interaction coefficients. The approach ... More
D=4, N=1 Supersymmetric Henneaux-Knaepen ModelsNov 19 1998We construct N=1 supersymmetric versions of four-dimensional Freedman-Townsend models and generalizations thereof found recently by Henneaux and Knaepen, with couplings between 1-form and 2-form gauge potentials. The models are presented both in a superfield ... More
Environment induced pre-thermalization in the Mott-Hubbard modelAug 29 2018Via the hierarchy of correlations, we study the strongly interacting Fermi-Hubbard model in the Mott insulator state and couple it to a Markovian environment which constantly monitors the particle numbers $\hat n_\mu^\uparrow$ and $\hat n_\mu^\downarrow$ ... More
Atomic Diffusion in the Surface State of Mott Insulator NiS2Aug 20 2015We present resistivity measurements of Mott insulator NiS2 single crystals after heat treatment. We find a strong increase of the low temperature resistivity that relaxes back towards the pristine behaviour over several days with a time constant of 45 ... More
On the determination of anomalies in supersymmetric theoriesMay 30 1996Dec 03 1996We develop an efficient technique to compute anomalies in supersymmetric theories by combining the so-called nonlocal regularization method and superspace techniques. To illustrate the method we apply it to a four dimensional toy model with potentially ... More
Gradients on SetsMar 16 2018For a locally Lipschitz continuous function $f:X\to\mathbb{R}$ the generalized gradient $\partial f(x)$ of Clarke is used to develop some (set-valued) gradient on a set $A\subset X$. Existence, uniqueness and some approximation are considered for optimal ... More
Environmental gravitational decoherence and a tensor noise modelFeb 04 2015We discuss decrease of coherence in a massive system due to the emission of gravitational waves. In particular we investigate environmental gravitational decoherence in the context of an interference experiment. The time-evolution of the reduced density ... More
Dynamically assisted nuclear fusionFeb 12 2019We consider the prototypical deuterium-tritium fusion reaction. At intermediate initial kinetic energies (in the keV regime), a major bottle-neck of this reaction is the Coulomb barrier between the nuclei, which is overcome by tunneling. Here, we study ... More
A unified approach to symmetry for semilinear equations associated to the Laplacian in $\mathbb{R}^N$Mar 20 2019We show radial symmetry of positive solutions to the H\'{e}non equation $-\Delta u = |x|^{-\ell} u^q $ in $\mathbb{R}^N \setminus \{ 0\} $, where $\ell \geq 0$, $q>0$ and satisfy further technical conditions. A new ingredient is a maximum principle for ... More
Efficient electrical spin readout of NV- centers in diamondAug 08 2016Using pulsed photoionization the coherent spin manipulation and echo formation of ensembles of NV- centers in diamond are detected electrically realizing contrasts of up to 17 %. The underlying spin-dependent ionization dynamics are investigated experimentally ... More
Tracking Temperature Dependent Relaxation Times of Individual Ferritin Nanomagnets with a Wide-band Quantum SpectrometerJun 02 2014We demonstrate the tracking of the spin dynamics of ensemble and individual magnetic ferritin proteins from cryogenic up to room temperature using the nitrogen-vacancy color center in diamond as magnetic sensor. We employ different detection protocols ... More
High-dynamic-range imaging of nanoscale magnetic fields using optimal control of a single qubitJul 24 2013We present a novel spectroscopy protocol based on optimal control of a single quantum system. It enables measurements with quantum-limited sensitivity (\eta_\omega ~ 1/sqrt(T_2^*),T_2^* denoting the system's coherence time) but has an orders of magnitude ... More
High-Resolution Correlation Spectroscopy of 13C Spins Near a Nitrogen-Vacancy Center in DiamondMay 07 2013Spin complexes comprising the nitrogen-vacancy (NV) center and neighboring spins are being considered as a building block for a new generation of spintronic and quantum information processing devices. Because assembling identical spin clusters is difficult, ... More
A Planar Scanning Probe MicroscopeMay 08 2018Scanning probe microscopy (SPM) is traditionally based on very sharp tips, where the small size of the apex is critical for resolution. This paradigm is about to shift, since a novel generation of planar probes (color centers in diamond, superconducting ... More
Identifying Word Translations in Non-Parallel TextsMay 22 1995Common algorithms for sentence and word-alignment allow the automatic identification of word translations from parallel texts. This study suggests that the identification of word translations should also be possible with non-parallel and even unrelated ... More
The Strangeness Signal in Hadron Production at Relativistic EnergyDec 02 2003Strangeness enhancement is discussed as a feature specific to relativistic nuclear collisions which create a fireball of strongly interacting matter at high energy density. At very high energy this is suggested to be partonic matter, but at lower energy ... More
Hadron Production in Relativistic Nuclear CollisionsDec 19 2002May 14 2003Relativistic nucleus-nucleus collisions create a "fireball" of strongly interacting matter at high energy density. At very high energy this is suggested to be partonic matter, but at lower energy it should consist of yet unknown hadronic, perhaps coherent ... More
Variational description of multi-fluid hydrodynamics: Uncharged fluidsSep 06 2002Jan 09 2007We present a formalism for Newtonian multi-fluid hydrodynamics derived from an unconstrained variational principle. This approach provides a natural way of obtaining the general equations of motion for a wide range of hydrodynamic systems containing an ... More
Covariant Vortex In Superconducting-Superfluid-Normal Fluid Mixtures with Stiff Equation of StateApr 26 2000The integrals of motion for a cylindrically symmetric stationary vortex are obtained in a covariant description of a mixture of interacting superconductors, superfluids and normal fluids. The relevant integrated stress-energy coefficients for the vortex ... More
Relativistic Nucleus-Nucleus Collisions and the QCD Matter Phase DiagramJul 10 2008This review will be concerned with our knowledge of extended matter under the governance of strong interaction, in short: QCD matter. Strictly speaking, the hadrons are representing the first layer of extended QCD architecture. In fact we encounter the ... More
A norm - inequality related to affine regular hexagonsJun 30 2011Let $(E, \lVert . \rVert)$ be a two-dimensional real normed space with unit sphere $S = \{x \in E, \lVert x \rVert = 1\}$. The main result of this paper is the following: Consider an affine regular hexagon with vertex set $H = \{\pm v_1, \pm v_2, \pm ... More
An extension of the Yamada-Watanabe condition for pathwise uniqueness to stochastic differential equations with jumpsJun 09 2009Oct 12 2009We extend the Yamada-Watanabe condition for pathwise uniqueness to stochastic differential equations with jumps, in the special case where small jumps are summable.
Optimal decay rate for the wave equation on a square with constant damping on a stripJul 13 2016Mar 02 2017We consider the damped wave equation with Dirichlet boundary conditions on the unit square. We assume the damping to be a characteristic function of a strip. We prove the exact $t^{-4/3}$-decay rate for the energy of classical solutions. This answers ... More
Reduction of Coupling ParametersNov 01 1995The general theory of the reduction in the number of coupling parameters is discussed. The method involves renormalization group invariant relations between couplings. It is more general than the imposition of symmetries. There are reduced theories with ... More
On the Analytic Structure of Hadronic Amplitudes in QCDDec 21 1992Analytic properties of hadronic amplitudes are discussed within the framework of QCD as formulated on the basis of the BRST algebra. Local, composite fields are introduced for hadrons. Given confinement, it is shown that hadronic amplitudes have no thresholds ... More
Isovariant mappings of degree 1 and the Gap HypothesisApr 03 2009Unpublished results of S Straus and W Browder state that two notions of homotopy equivalence for manifolds with smooth group actions - isovariant and equivariant - often coincide under a condition called the Gap Hypothesis; the proofs use deep results ... More
Tree setsDec 11 2015Feb 27 2017We study an abstract notion of tree structure which lies at the common core of various tree-like discrete structures commonly used in combinatorics: trees in graphs, order trees, nested subsets of a set, tree-decompositions of graphs and matroids etc. ... More
Intensional Models for the Theory of TypesAug 23 2006In this paper we define intensional models for the classical theory of types, thus arriving at an intensional type logic ITL. Intensional models generalize Henkin's general models and have a natural definition. As a class they do not validate the axiom ... More
Dispersion Relations in Quantum ChromodynamicsMay 26 1992Dispersion relations for the scattering of hadrons are considered within the framework of Quantum Chromodynamics. It is argued that the original methods of proof remain applicable. The setting and the spectral conditions are provided by an appropriate ... More
Two-locus clines on the real line with a step environmentAug 11 2017The shape of allele-frequency clines maintained by migration-selection balance depends not only on the properties of migration and selection, but also on the dominance relations among alleles and on linkage to other loci under selection. We investigate ... More
A time inhomogeneous Cox-Ingersoll-Ross diffusion with jumpsJun 10 2009We consider a time inhomogeneous Cox-Ingersoll-Ross diffusion with positive jumps. We exploit a branching property to prove existence of a unique strong solution under a restrictive condition on the jump measure. We give Laplace transforms for the transition ... More
A quantified Tauberian theorem and local decay of $C_0$-semigroupsMay 10 2017We prove a quantified Tauberian theorem for functions under a new kind of Tauberian condition. In this condition we assume in particular that the Laplace transform of the considered function extends to a domain to the left of the imaginary axis, given ... More
On the decay rate for the wave equation with viscoelastic boundary dampingJan 04 2017Sep 05 2017We consider the wave equation with a boundary condition of memory type. Under natural conditions on the acoustic impedance $\hat{k}$ of the boundary one can define a corresponding semigroup of contractions (Desch, Fasangova, Milota, Probst 2010). With ... More
Selected Topics from Top Mass Measurements at the TevatronDec 07 2016The most recent results of the top-quark mass measurements at the Tevatron at Fermilab are presented. Data were collected in proton-antiproton collisions at sqrt{s}=1.96 TeV by the CDF and D0 experiments. Top quark mass measurements in the lepton+jets, ... More
Superconvergence, Confinement and DualityNov 02 1995Arguments for the confinement of transverse gauge field excitations, which are based upon superconvergence relations of the propagator, and upon the BRST algebra, are reviewed and applied to supersymmetric models. They are shown to be in agreement with ... More
Analytic Structure of Amplitudes in Gauge Theories with ConfinementDec 05 1994For gauge theories with confinement, the analytic structure of amplitudes is explored. It is shown that the analytic properties of physical amplitudes are the same as those obtained on the basis of an effective theory involving only the composite, physical ... More
Locally finite graphs with ends: a topological approachDec 21 2009Jul 10 2012This paper is intended as an introductory survey of a newly emerging field: a topological approach to the study of locally finite graphs that crucially incorporates their ends. Topological arcs and circles, which may pass through ends, assume the role ... More
Abstract Separation SystemsJun 15 2014Apr 17 2017Abstract separation systems provide a simple general framework in which both tree-shape and high cohesion of many combinatorial structures can be expressed, and their duality proved. Applications range from tangle-type duality and tree structure theorems ... More
Local decay of $C_0$-semigroups with a possible singularity of logarithmic type at zeroOct 29 2017We prove decay rates for a vector-valued function $f$ of a non-negative real variable with bounded weak derivative, under rather general conditions on the Laplace transform $\hat{f}$. This generalizes results of Batty-Duyckaerts (2008) and other authors ... More
To which extent is the membrane potential in a neuron between successive spikes adequately modelled by a (continuous) semimartingale?Aug 25 2010We consider $p$-variations in some membrane potential data --viewed as a function of the step size in case where $p$ is fixed, or viewed as a function of $p$ in case where the step size is fixed-- and compare their shape with results in Ait-Sahalia and ... More
A Survey on Migration-Selection Models in Population GeneticsSep 10 2013This survey focuses on the most important aspects of the mathematical theory of population genetic models of selection and migration between discrete niches. Such models are most appropriate if the dispersal distance is short compared to the scale at ... More
Distance dependence of entanglement generation via a bosonic heat bathDec 19 2008Apr 16 2009Within a generalized Caldeira-Leggett model we analyze the conditions under which a bosonic heat bath can entangle two microscopic quantum systems at a distance $r$. We find that the attainable entanglement is extremely distance-sensitive. Significant ... More
A weighted isoperimetric inequality in a wedgeOct 04 2012Let $c, k_1,..., k_N $ be non-negative numbers, and define a measure $\mu $ in the wedge $W:= \{x\in \mathbb{R} ^N :\, x_i >0, i=1,...,N\} $ by $d\mu = e^{c|x|^2} x_1 ^{k_1}...x_N ^{k_N} \, dx $. It is shown that among all measurable subsets of $W$ with ... More
Excitations in photoactive molecules from quantum Monte CarloApr 21 2004Despite significant advances in electronic structure methods for the treatment of excited states, attaining an accurate description of the photoinduced processes in photoactive biomolecules is proving very difficult. For the prototypical photosensitive ... More
Asymptotically anti-de Sitter space-times: symmetries and conservation laws revisitedJun 25 2003In this short note, we verify explicitly in static coordinates that the non trivial asymptotic Killing vectors at spatial infinity for anti-de Sitter space-times correspond one to one to the conformal Killing vectors of the conformally flat metric induced ... More
Global Symmetries in the Antifield-FormalismJun 26 1996In this paper, two things are done. (i) First, it is shown that any global symmetry of a gauge-invariant theory can be extended to the ghosts and the antifields so as to leave invariant the solution of the master-equation (before gauge fixing). (ii) Second, ... More
BRST-Antibracket Cohomology in 2D Conformal GravityJul 12 1994We present results of a computation of the BRST-antibracket cohomology in the space of local functionals of the fields and antifields for a class of 2d gravitational theories which are conformally invariant at the classical level. In particular all classical ... More
Exotic Gauge Theories from Tensor CalculusOct 22 1999Jan 30 2000We construct non-standard interactions between exterior form gauge fields by gauging a particular global symmetry of the Einstein-Maxwell action for such fields. Furthermore we discuss generalizations of such interactions by adding couplings to gravitational ... More
An isoperimetric inequality for Gauss--like product measuresApr 20 2015This paper deals with various questions related to the isoperimetic problem for smooth positive measure $d\mu = \varphi(x)dx$, with $x \in \Omega \subset \mathbb{R}^N$. Firstly we find some necessary conditions on the density of the measure $ \varphi(x)$ ... More
Sauter-Schwinger like tunneling in tilted Bose-Hubbard lattices in the Mott phaseJul 19 2011We study the Mott phase of the Bose-Hubbard model on a tilted lattice. On the (Gutzwiller) mean-field level, the tilt has no effect -- but quantum fluctuations entail particle-hole pair creation via tunneling. For small potential gradients (long-wavelength ... More
Cosmological Constant from DecoherenceOct 26 2010Jun 03 2011We address the issue why a cosmological constant (dark energy) possesses a small positive value instead of being zero. Motivated by the cosmic landscape picture, we mimic the dark energy by a scalar field with potential wells and show that other degrees ... More
A Distributed Magnetometer NetworkSep 19 2014Sep 30 2014Various possiblities for a distributed magnetometer network are considered. We discuss strategies such as croudsourcing smartphone magnetometer data, the use of trees as magnetometers, and performing interferometry using magnetometer arrays to synthesize ... More
Surrogate Gradient Learning in Spiking Neural NetworksJan 28 2019A growing number of neuromorphic spiking neural network processors that emulate biological neural networks create an imminent need for methods and tools to enable them to solve real-world signal processing problems. Like conventional neural networks, ... More
Cohomological analysis of bosonic D-strings and 2d sigma models coupled to abelian gauge fieldsDec 12 1997Apr 14 1998We analyse completely the BRST cohomology on local functionals for two dimensional sigma models coupled to abelian world sheet gauge fields, including effective bosonic D-string models described by Born-Infeld actions. In particular we prove that the ... More
The rigid symmetries of bosonic D-stringsJul 07 1997We analyse the classical symmetries of bosonic D-string actions and generalizations thereof. Among others, we show that the simplest actions of this type have infinitely many nontrivial rigid symmetries which act nontrivially and nonlinearly both on the ... More
Entanglement of remote quantum systems by environmental modesNov 23 2011Nov 25 2011We investigate the generation of quantum mechanical entanglement of two remote oscillators that are locally coupled to a common bosonic bath. Starting with a Lagrangian formulation of a suitable model, we derive two coupled Quantum Langevin Equations ... More
Surrogate Gradient Learning in Spiking Neural NetworksJan 28 2019May 03 2019Spiking neural networks are nature's versatile solution to fault-tolerant and energy efficient signal processing. To translate these benefits into hardware, a growing number of neuromorphic spiking neural network processors attempt to emulate biological ... More
Weighted isoperimetric inequalities in cones and applicationsJul 27 2011May 17 2012This paper deals with weighted isoperimetric inequalities relative to cones of $\mathbb{R}^{N}$. We study the structure of measures that admit as isoperimetric sets the intersection of a cone with balls centered at the vertex of the cone. For instance, ... More
Nano-engineered Diamond Waveguide as a Robust Bright Platform for Nanomagnetometry Using Shallow Nitrogen Vacancy CentersAug 29 2014Dec 16 2014Photonic structures in diamond are key to most of its application in quantum technology. Here, we demonstrate tapered nano-waveguides structured directly onto the diamond substrate hosting shallow-implanted nitrogen vacancy (NV) centers. By optimization ... More
Relaxometry and dephasing imaging of superparamagnetic magnetite nanoparticles using a single qubitMay 11 2015Oct 26 2015To study the magnetic dynamics of superparamagnetic nanoparticles we use scanning probe relaxometry and dephasing of the nitrogen-vacancy (NV) center in diamond, characterizing the spin-noise of a single 10-nm magnetite particle. Additionally, we show ... More
Augmenting the spin properties of shallow implanted NV-centers by CVD-overgrowthAug 21 2012The controlled scaling of diamond defect center based quantum registers relies on the ability to position NVs with high spatial resolution. Using ion implantation, shallow (< 10 nm) NVs can be placed with accuracy below 20nm, but generally show reduced ... More
Measurement of the Sigma pi photoproduction line shapes near the Lambda(1405)Jan 21 2013Jan 24 2013The reaction gamma + p -> K+ + Sigma + pi was used to determine the invariant mass distributions or "line shapes" of the Sigma+ pi-, Sigma- pi+ and Sigma0 pi0 final states, from threshold at 1328 MeV/c^2 through the mass range of the Lambda(1405) and ... More
Generalized Line Spectral Estimation via Convex OptimizationSep 26 2016Line spectral estimation is the problem of recovering the frequencies and amplitudes of a mixture of a few sinusoids from equispaced samples. However, in a variety of signal processing problems arising in imaging, radar, and localization we do not have ... More
Compressive Identification of Linear OperatorsMay 26 2011We consider the problem of identifying a linear deterministic operator from an input-output measurement. For the large class of continuous (and hence bounded) operators, under additional mild restrictions, we show that stable identifiability is possible ... More
Force-extension curves of bacterial flagellaNov 10 2010Bacterial flagella assume different helical shapes during the tumbling phase of a bacterium but also in response to varying environmental conditions. Force-extension measurements by Darnton and Berg explicitly demonstrate a transformation from the coiled ... More
Compactifications, Hartman functions and (weak) almost periodicityOct 04 2005Oct 10 2008In this paper we investigate Hartman functions on a topological group $G$. Recall that $(\iota, C)$ is a group compactification of $G$ if $C$ is a compact group, $\iota: G\to C$ is a continuous group homomorphism and $\iota(G)$ is dense in $C$. A complex-valued ... More
Cosmic ray transport in partially turbulent space plasmas with compressible magnetic turbulenceNov 18 2011Recently a new transport theory of cosmic rays in magnetized space plasmas extending the quasilinear approximation to the particle orbit has been developed for the case of an axisymmetric incompressible magnetic turbulence. Here we generalize the approach ... More
An applicative theory for FPHJan 28 2011In this paper we introduce an applicative theory which characterizes the polynomial hierarchy of time.
On the homology of locally finite graphsOct 29 2009We show that the topological cycle space of a locally finite graph is a canonical quotient of the first singular homology group of its Freudenthal compactification, and we characterize the graphs for which the two coincide. We construct a new singular-type ... More
Spin, Statistics, and Reflections, II. Lorentz InvarianceDec 21 2005The analysis of the relation between modular P$_1$CT-symmetry -- a consequence of the Unruh effect -- and Pauli's spin-statistics relation is continued. The result in the predecessor to this article is extended to the Lorentz symmetric situation. A model ... More
optimParallel: an R Package Providing Parallel Versions of the Gradient-Based Optimization Methods of optim()Apr 30 2018The R package optimParallel provides a parallel version of the gradient-based optimization methods of optim(). The main function of the package is optimParallel(), which has the same usage and output as optim(). Using optimParallel() can significantly ... More
Combining Heterogeneous Spatial Datasets with Process-based Spatial Fusion Models: A Unifying FrameworkJun 02 2019In modern spatial statistics, the structure of data that is collected has become more heterogeneous. Depending on the type of spatial data, different modeling strategies for spatial data are used. For example, a kriging approach for geostatistical data; ... More
Analytic Structure of the Quark Propagator in a Model with an infrared vanishing Gluon PropagatorNov 11 1994Oct 12 1995The Dyson-Schwinger equation for the quark self energy is solved in rainbow approximation using an infrared (IR) vanishing gluon propagator that introduces an IR mass scale $b$. There exists a $b$ dependent critical coupling indicating the spontaneous ... More
Phase transitions in systems with two species of molecular motorsFeb 06 2004Systems with two species of active molecular motors moving on (cytoskeletal) filaments into opposite directions are studied theoretically using driven lattice gas models. The motors can unbind from and rebind to the filaments. Two motors are more likely ... More
Traffic of molecular motors through tube-like compartmentsApr 30 2003The traffic of molecular motors through open tube-like compartments is studied using lattice models. These models exhibit boundary-induced phase transitions related to those of the asymmetric simple exclusion process (ASEP) in one dimension. The location ... More
Adiabatic oscillations of non-rotating superfluid neutron starsApr 30 2002We present results concerning the linear (radial and non-radial) oscillations of non-rotating superfluid neutron stars in Newtonian physics. We use a simple two-fluid model to describe the superfluid neutron star, where one fluid consists of the superfluid ... More
An Approximate Sign Sum Rule for the Transmission Amplitude Through a Quantum DotJul 14 1999We study the phase of the transmission amplitude through a disordered quantum dot in the Coulomb blockade regime. We calculate the phase dependence on gate voltage for a disorder configuration. We show that over a ``period'', consisting of a resonance ... More
Global parameter-space correlations of coherent searches for continuous gravitational wavesApr 01 2005The space of phase-parameters (sky-position, frequency, spindowns) of a coherent matched-filtering search for continuous gravitational waves from isolated neutron stars shows strong global correlations (``circles in the sky''). In the local limit this ... More
On the homology of locally compact spaces with endsOct 29 2009May 25 2011We propose a homology theory for locally compact spaces with ends in which the ends play a special role. The approach is motivated by results for graphs with ends, where it has been highly successful. But it was unclear how the original graph-theoretical ... More
Derived and Residual Subspace DesignsMay 21 2014A generalization of forming derived and residual designs from $t$-designs to subspace designs is proposed. A $q$-analog of a theorem by Van Trung, van Leijenhorst and Driessen is proven, stating that if for some (not necessarily realizable) parameter ... More