Results for "Michael Engel"

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Room-Temperature Quantum-Confined Stark Effect in Atomically Thin SemiconductorFeb 08 2018Electric field-controlled, two-dimensional (2D) exciton dynamics in transition metal dichalcogenide monolayers is a current research focus in condensed matter physics. We have experimentally investigated the spectral and temporal properties of the A-exciton ... More
On sets of eigenvalues of matrices with prescribed row sums and prescribed graphDec 10 2013Motivated by a work of Boros, Brualdi, Crama and Hoffman, we consider the sets of (i) possible Perron roots of nonnegative matrices with prescribed row sums and associated graph, and (ii) possible eigenvalues of complex matrices with prescribed associated ... More
Anomalous Longitudinal Shower Profiles and Hadronic InteractionsNov 02 2011The bulk of air showers initiated by very high energy cosmic rays exhibits a longitudinal development in depth with a single well-defined shower maximum. However, a small fraction of showers has a profile that differs considerably from this average behaviour. ... More
Newton's Inequalities on a LatticeFeb 11 2010Jun 14 2010Functions that satisfy the Hadamard Fisher Inequalities also satisfy Newton's Inequalities
Complexity in surfaces of densest packings for families of polyhedraSep 10 2013Packings of hard polyhedra have been studied for centuries due to their mathematical aesthetic and more recently for their applications in fields such as nanoscience, granular and colloidal matter, and biology. In all these fields, particle shape is important ... More
A metric for wettability at the nanoscaleAug 29 2016Wettability is the affinity of a liquid for a solid surface. For energetic reasons, macroscopic drops of liquid are nearly spherical away from interfaces with solids, and any local deformations due to molecular-scale surface interactions are negligible. ... More
High-quality dry transferred CVD bilayer grapheneApr 14 2017We report on the fabrication and characterization of high-quality chemical vapor-deposited (CVD) bilayer graphene (BLG). In particular, we demonstrate that CVD-grown BLG can mechanically be detached from the copper foil by an hexagonal boron nitride (hBN) ... More
Controlling Chirality of Entropic CrystalsJul 14 2015Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, so far homochiral colloidal crystals, which are candidates for photonic ... More
Ballistic transport exceeding 28 μm in CVD grown grapheneNov 27 2015Jan 12 2016We report on ballistic transport over more than 28 \mu m in graphene grown by chemical vapor deposition (CVD) that is fully encapsulated in hexagonal boron nitride. The structures are fabricated by an advanced dry van-der-Waals transfer method and exhibit ... More
Hard-disk equation of state: First-order liquid-hexatic transition in two dimensions with three simulation methodsNov 07 2012Apr 24 2013We report large-scale computer simulations of the hard-disk system at high densities in the region of the melting transition. Our simulations reproduce the equation of state, previously obtained using the event-chain Monte Carlo algorithm, with a massively ... More
Rough index theory on spaces of polynomial growth and contractibilityMay 15 2015Jul 24 2015We will show for a polynomially contractible manifold M of bounded geometry and of polynomial volume growth that every coarse cohomology class of M pairs continuously against the K-theory of the uniform Roe algebra of M. From this we will conclude that ... More
Log-concavity of the overpartition functionDec 15 2014Dec 22 2014We prove that the overpartition function is log-concave for all n>1. The proof is based on Sills Rademacher type series for the overpartition function and inspired by Desalvo and Pak's proof for the partition function.
Fast radio bursts: the observational case for a Galactic originJul 03 2015Sep 08 2015There are by now ten published detections of fast radio bursts (FRBs), single bright GHz-band millisecond pulses of unknown origin. Proposed explanations cover a broad range from exotic processes at cosmological distances to atmospheric and terrestrial ... More
Multifractality and percolation in the coupling space of perceptronsAug 21 1996Jan 13 1997The coupling space of perceptrons with continuous as well as with binary weights gets partitioned into a disordered multifractal by a set of $p=\gamma N$ random input patterns. The multifractal spectrum $f(\alpha)$ can be calculated analytically using ... More
Stability of the replica-symmetric saddle-point in general mean-field spin-glass modelsAug 10 2010Within the replica approach to mean-field spin-glasses the transition from ergodic high-temperature behaviour to the glassy low-temperature phase is marked by the instability of the replica-symmetric saddle-point. For general spin-glass models with non-Gaussian ... More
Chiral condensate in nf=2 QCD from the Banks-Casher relationNov 27 2014Dec 03 2014Exploiting the Banks-Casher relation, we present a direct determination of the chiral condensate in two-flavor QCD, computing the mode number of the O(a)-improved Wilson-Dirac operator below various cutoffs. We make use of CLS-configurations with three ... More
Controlled self-assembly of periodic and aperiodic cluster crystalsJan 17 2014Soft particles are known to overlap and form stable clusters that self-assemble into periodic crystalline phases with density-independent lattice constants. We use molecular dynamics simulations in two dimensions to demonstrate that, through a judicious ... More
Hadronic Multiparticle Production at Ultra-High Energies and Extensive Air ShowersOct 20 2010Studies of the nature of cosmic ray particles at the highest energies are based on the measurement of extensive air showers. Most cosmic ray properties can therefore only be obtained from the interpretation of air shower data and are thus depending on ... More
The Habitable Zone Planet Finder: A Proposed High Resolution NIR Spectrograph for the Hobby Eberly Telescope to Discover Low Mass Exoplanets around M DwarfsJul 19 2010The Habitable Zone Planet Finder (HZPF) is a proposed instrument for the 10m class Hobby Eberly telescope that will be capable of discovering low mass planets around M dwarfs. HZPF will be fiber-fed, provide a spectral resolution R~ 50,000 and cover the ... More
The Muon Anomalous Magnetic Moment and the Pion PolarizabilitySep 09 2013We compute the charged pion loop contribution to the muon anomalous magnetic moment $a_\mu$, taking into account the effect of the charged pion polarizability, $(\alpha_1-\beta_1)_{\pi^+}$. We evaluate this contribution using two different models that ... More
Changes in r-process abundances at late timesMar 19 2001We explore changes in abundance patterns that occur late in the r process. As the neutrons available for capture begin to disappear, a quasiequilibrium funnel shifts material into the large peaks at A=130 and A=195, and into the rare-earth "bump" at A=160. ... More
Neutrino capture by r-process waiting-point nucleiMay 04 1998We use the Quasiparticle Random Phase Approximation to include the effects of low-lying Gamow-Teller and first forbidden strength in neutrino capture by very neutron-rich nuclei with N = 50, 82, or 126. For electron neutrinos in what is currently considered ... More
A black phosphorus photo-detector for multispectral, high-resolution imagingJul 09 2014Jul 30 2014Black phosphorus is a layered semiconductor that is intensely researched in view of applications in optoelectronics. In this Letter, we investigate a multi-layer black phosphorus photo-detector that is capable of acquiring high-contrast (V>0.9) images ... More
Confirmation of the random tiling hypothesis for a decagonal quasicrystalOct 16 2012Mechanisms that stabilize quasicrystals are much discussed but not finally resolved. We confirm the random tiling hypothesis and its predictions in a fully atomistic decagonal quasicrystal model by calculating the free energy and the phason elastic constants ... More
Burghelea conjecture and asymptotic dimension of groupsOct 31 2016We review the Burghelea conjecture, which constitutes a full computation of the periodic cyclic homology of complex group rings, and its relation to the algebraic Baum-Connes conjecture. The Burghelea conjecture implies the Bass conjecture. We state two ... More
Analytical approximations for spiral wavesJan 26 2013Sep 20 2013We propose a non-perturbative attempt to solve the kinematic equations for spiral waves in excitable media. From the eikonal equation for the wave front we derive an implicit analytical relation between rotation frequency $\Omega$ and core radius $R_{0}$. ... More
Detection of Single Spin Decoherence in a Quantum Dot via Charge CurrentsNov 10 2000We consider a quantum dot attached to leads in the Coulomb blockade regime which has a spin 1/2 ground state. We show that by applying an ESR field to the dot-spin the stationary current in the sequential tunneling regime exhibits a resonance whose line ... More
Conductance fluctuations in diffusive rings: Berry phase effects and criteria for adiabaticityFeb 25 2000Jul 18 2000We study Berry phase effects on conductance properties of diffusive mesoscopic conductors, which are caused by an electron spin moving through an orientationally inhomogeneous magnetic field. Extending previous work, we start with an exact, i.e. not assuming ... More
On the measurement of the proton-air cross section using longitudinal shower profilesDec 08 2006In this paper, we will discuss the prospects of deducing the proton-air cross section from fluorescence telescope measurements of extensive air showers. As it is not possible to observe the point of first interaction $X_{\rm 1}$ directly, other observables ... More
On the measurement of the proton-air cross section using air shower dataMar 02 2009May 14 2009The analysis of high-energy air shower data allows one to study the proton-air cross section at energies beyond the reach of fixed target and collider experiments. The mean depth of the first interaction point and its fluctuations are a measure of the ... More
On the measurement of the proton-air cross section using cosmic ray dataSep 10 2007Cosmic ray data may allow the determination of the proton-air cross section at ultra-high energy. For example, the distribution of the first interaction point in air showers reflects the particle production cross section. As it is not possible to observe ... More
Origin of photoresponse in black phosphorus photo-transistorsJul 27 2014We study the origin of photocurrent generated in doped multilayer BP photo-transistors, and find that it is dominated by thermally driven thermoelectric and bolometric processes. The experimentally observed photocurrent polarities are consistent with ... More
Hadronic Light-by-Light and the Pion PolarizabilityJan 04 2012Jan 13 2012We compute the charged pion loop contribution to the light-by-light scattering amplitude for off-shell photons in chiral perturbation theory through next-to-leading order (NLO). We show that NLO contributions are relatively more important due to a fortuitous ... More
Proton-Air Cross Section and Extensive Air ShowersJun 17 2009Hadronic cross sections at ultra-high energy have a significant impact on the development of extensive air shower cascades. Therefore the interpretation of air shower data depends critically on hadronic interaction models that extrapolate the cross section ... More
Power dissipation and electrical breakdown in black phosphorusJul 02 2015We report operating temperatures and heating coefficients measured in a multi-layer black phosphorus device as a function of injected electrical power. By combining micro-Raman spectroscopy and electrical transport measurements, we have observed a linear ... More
Phason Dynamics in One-Dimensional LatticesFeb 09 2010In quasicrystals, the phason degree of freedom and the inherent anharmonic potentials lead to complex dynamics which cannot be described by the usual phonon modes of motion. We have constructed simple one-dimensional model systems, the dynamic Fibonacci ... More
Dynamics of particle flips in two-dimensional quasicrystalsJun 09 2010Oct 08 2010The dynamics of quasicrystals is more complicated than the dynamics of periodic solids and difficult to study in experiments. Here, we investigate a decagonal and a dodecagonal quasicrystal using molecular dynamics simulations of the Lennard-Jones-Gauss ... More
Electric Dipole Moments of Nucleons, Nuclei, and Atoms: The Standard Model and BeyondMar 10 2013Searches for the permanent electric dipole moments (EDMs) of molecules, atoms, nucleons and nuclei provide powerful probes of CP violation both within and beyond the Standard Model (BSM). The interpretation of experimental EDM limits requires careful ... More
Asymmetric Quantum Shot Noise in Quantum DotsDec 03 2003We analyze the frequency-dependent noise of a current through a quantum dot which is coupled to Fermi leads and which is in the Coulomb blockade regime. We show that the asymmetric shot noise as function of frequency shows steps and becomes super-Poissonian. ... More
Dense crystalline dimer packings of regular tetrahedraJan 05 2010Jul 25 2010We present the densest known packing of regular tetrahedra with density phi = 4000/4671 = 0.856347... Like the recently discovered packings of Kallus et al. [arXiv:0910.5226] and Torquato-Jiao [arXiv:0912.4210], our packing is crystalline with a unit ... More
Thermodynamics of the Lévy spin glassJun 15 2010We investigate the L\'evy glass, a mean-field spin glass model with power-law distributed couplings characterized by a divergent second moment. By combining extensively many small couplings with a spare random backbone of strong bonds the model is intermediate ... More
Replica theory for Levy spin glassesJan 28 2008Infinite-range spin-glass models with Levy-distributed interactions show a spin-glass transition with similarities to both the Sherrington-Kirkpatrick model and to disordered spin systems on finite connectivity random graphs. Despite the diverging moments ... More
Spintronics and Quantum Dots for Quantum Computing and Quantum CommunicationApr 11 2000Jun 08 2000Control over electron-spin states, such as coherent manipulation, filtering and measurement promises access to new technologies in conventional as well as in quantum computation and quantum communication. We review our proposal of using electron spins ... More
The Dilworth Number of Auto-Chordal-Bipartite GraphsSep 23 2013The mirror (or bipartite complement) mir(B) of a bipartite graph B=(X,Y,E) has the same color classes X and Y as B, and two vertices x in X and y in Y are adjacent in mir(B) if and only if xy is not in E. A bipartite graph is chordal bipartite if none ... More
Simulating Electron Transport and Synchrotron Emission in Radio Galaxies: Shock Acceleration and Synchrotron Aging in Axis-Symmetric FlowsSep 07 1998We introduce a simple and economical but effective method for including relativistic electron transport in multi-dimensional simulations of radio galaxies. The method is designed to follow explicitly diffusive acceleration at shocks, and, in smooth flows ... More
Direct Sparse OdometryJul 09 2016We propose a novel direct sparse visual odometry formulation. It combines a fully direct probabilistic model (minimizing a photometric error) with consistent, joint optimization of all model parameters, including geometry -- represented as inverse depth ... More
Phase Transition in Multiprocessor SchedulingAug 05 2002Aug 21 2002The problem of distributing the workload on a parallel computer to minimize the overall runtime is known as Multiprocessor Scheduling Problem. It is NP-hard, but like many other NP-hard problems, the average hardness of random instances displays an ``easy-hard'' ... More
Spatial Confinement Causes Lifetime Enhancement and Expansion of Vortex Rings with Positive Filament TensionJan 25 2014Jun 30 2015We study the impact of spatial confinement on the dynamics of three-dimensional excitation vortices with circular filaments. In a chemically active medium we observe a decreased contraction of such scroll rings and even expanding ones, despite of their ... More
Propagation Of Waves In Periodic-Heterogeneous Bistable SystemsMar 21 2012Wave propagation in one-dimensional heterogeneous bistable media is studied using the Schl\"ogl model as a representative example. Starting from the analytically known traveling wave solution for the homogeneous medium, infinitely extended, spatially ... More
Front propagation in three-dimensional corrugated reaction-diffusion mediaJun 29 2014Sep 15 2014Propagation of traveling fronts in three-dimensional reaction-diffusion media with spatially modulated cross-section is studied using the Schl\"ogl model as a representative example. Applying appropriate perturbation techniques leads first to a reduction ... More
Three-Dimensional Autonomous Pacemaker in the Photosensitive Belousov-Zhabotinsky mediumJun 23 2014Dec 08 2014In experiments with the photosensitive Belousov-Zhabotinsky reaction (PBZR) we found a stable three-dimensional organizing center that periodically emits trigger waves of chemical concentration. The experiments are performed in a parameter regime with ... More
Observation of Faraday Waves in a Bose-Einstein CondensateJan 01 2007Faraday waves in a cigar-shaped Bose-Einstein condensate are created. It is shown that periodically modulating the transverse confinement, and thus the nonlinear interactions in the BEC, excites small amplitude longitudinal oscillations through a parametric ... More
Wave propagation in spatially modulated tubesJun 01 2016We investigate wave propagation in rotationally symmetric tubes with a periodic spatial modulation of cross section. Using an asymptotic perturbation analysis, the governing quasi two-dimensional reaction-diffusion equation can be reduced into a one-dimensional ... More
Shaping wave patterns in reaction-diffusion systemsMay 16 2014Dec 12 2014We present a method to control the two-dimensional shape of traveling wave solutions to reaction-diffusion systems, as e.g. interfaces and excitation pulses. Control signals that realize a pre-given wave shape are determined analytically from nonlinear ... More
Probing Single-Electron Spin Decoherence in Quantum Dots using Charged ExcitonsAug 20 2004We propose to use optical detection of magnetic resonance (ODMR) to measure the decoherence time T_{2} of a single electron spin in a semiconductor quantum dot. The electron is in one of the spin 1/2 states and a circularly polarized laser can only create ... More
Exact and Positive Controllability of Boundary Control SystemsOct 04 2016Using the semigroup approach to abstract boundary control problems we characterize the space of all exactly reachable states. Moreover, we study the situation when the controls of the system are required to be positive. The abstract results are applied ... More
Emergent collective phenomena in a mixture of hard shapes through active rotationAug 09 2013We investigate collective phenomena with rotationally driven spinners of concave shape. Each spinner experiences a constant internal torque in either a clockwise or counterclockwise direction. Although the spinners are modeled as hard, otherwise non-interacting ... More
Probability of the resistive state formation caused by absorption of a single-photon in current-carrying superconducting nano-stripsOct 25 2004We have studied supercurrent-assisted formation of the resistive state in nano-structured Nb and NbN superconducting films after absorption of a single photon. In amorphous narrow NbN strips the probability of the resistive state formation has a pronounced ... More
Light-matter interaction in a microcavity-controlled graphene transistorDec 06 2011Jun 25 2012Graphene has extraordinary electronic and optical properties and holds great promise for applications in photonics and optoelectronics. Demonstrations including high-speed photodetectors, optical modulators, plasmonic devices, and ultrafast lasers have ... More
Understanding shape entropy through local dense packingSep 04 2013Oct 28 2014Entropy drives the phase behavior of colloids ranging from dense suspensions of hard spheres or rods to dilute suspensions of hard spheres and depletants. Entropic ordering of anisotropic shapes into complex crystals, liquid crystals, and even quasicrystals ... More
Entropically Patchy Particles: Engineering Valence through Shape EntropyApr 29 2013Feb 13 2014Patchy particles are a popular paradigm for the design and synthesis of nanoparticles and colloids for self-assembly. In "traditional" patchy particles, anisotropic interactions arising from patterned coatings, functionalized molecules, DNA, and other ... More
An ultra-fast superconducting Nb nanowire single-photon detector for soft X-raysAug 08 2012Sep 12 2012Although superconducting nanowire single-photon detectors (SNSPDs) are well studied regarding the detection of infrared/optical photons and keV-molecules, no studies on continuous X-ray photon counting by thick-film detectors have been reported so far. ... More
Fluid-to-solid transition of hard regular polygonsJun 02 2016Characterizing the fluid-to-solid transition (conversely the melting transition) of two-dimensional systems is a fundamental problem in condensed matter physics that has advanced significantly through the application of computational resources and algorithms. ... More
Sensitivity of Extensive Air Showers to Features of Hadronic Interactions at Ultra-High EnergiesJun 02 2009We study the dependence of extensive air shower development on the first hadronic interactions at ultra-high energies occurring in the startup phase of the air shower cascade. The interpretation of standard air shower observables depends on the characteristics ... More
Low-temperature structure of xi'-Al-Pd-Mn optimized by ab-initio methodsSep 08 2011Oct 27 2011We have studied and resolved occupancy correlations in the existing average structure model of the complex metallic alloy xi'-Al-Pd-Mn [Boudard et al., Phil. Mag. A, 74, 939 (1996)], which has approximately 320 atoms in the unit cell and many fractionally ... More
Massively parallel Monte Carlo for many-particle simulations on GPUsNov 07 2012Aug 23 2013Current trends in parallel processors call for the design of efficient massively parallel algorithms for scientific computing. Parallel algorithms for Monte Carlo simulations of thermodynamic ensembles of particles have received little attention because ... More
Packing and Self-assembly of Truncated Triangular BipyramidsApr 10 2013Aug 14 2013Motivated by breakthroughs in the synthesis of faceted nano- and colloidal particles, as well as theoretical and computational studies of their packings, we investigate a family of truncated triangular bipyramids. We report dense periodic packings with ... More
AGB and post-AGB starsAug 12 2005Intermediate mass stars (1-8 solar masses) evolve along the Asymptotic Giant Branch after completion of hydrogen and helium core burning. At the tip they lose for several ten to hundred thousand years copious amounts of mass and exhibit various forms ... More
Intrinsic-Density FunctionalsOct 10 2006The Hohenberg-Kohn theorem and Kohn-Sham procedure are extended to functionals of the localized intrinsic density of a self-bound system such as a nucleus. After defining the intrinsic-density functional, we modify the usual Kohn-Sham procedure slightly ... More
Wrong way maps in uniformly finite homology and homology of groupsFeb 10 2016Dec 01 2016Given a non-compact Riemannian manifold M and a submanifold N of codimension q, we will construct under certain assumptions on both M and N a wrong way map in uniformly finite homology. Using an equivariant version of the construction and applying it ... More
Oscillatory motion of sheared nanorods beyond the nematic phaseApr 03 2013Jun 26 2013We study the role of the control parameter triggering nematic order (temperature or concentration) on the dynamical behavior of a system of nanorods under shear. Our study is based on a set of mesoscopic equations of motion for the components of the tensorial ... More
QCD with Two Light Dynamical Chirally Improved Quarks: BaryonsJan 18 2013May 14 2013We present a study of baryon ground states and low lying excitations of non-strange and strange baryons. The results are based on seven gauge field ensembles with two dynamical light Chirally Improved (CI) quarks corresponding to pion masses between 255 ... More
Low-lying Lambda Baryons from the LatticeDec 10 2012Jan 14 2013In a lattice QCD calculation with two light dynamical Chirally Improved (CI) quarks we determine ground state and some excited state masses in all four Lambda baryon channels 1/2^\pm and 3/2^\pm. We perform an infinite volume extrapolation and confirm ... More
Chiral symmetry breaking in QCD LiteJun 19 2014A distinctive feature of the presence of spontaneous chiral symmetry breaking in QCD is the condensation of low modes of the Dirac operator near the origin. The rate of condensation must be equal to the slope of (Mpi^2 Fpi^2)/2 with respect to the quark ... More
Quantum-Hall plateau-plateau transition in top-gated epitaxial graphene grown on SiC (0001)Dec 19 2011Dec 20 2011We investigate the low-temperature magneto-transport properties of monolayer epitaxial graphene films formed on the Si-face of semi-insulating 4H-SiC substrates by a high temperature sublimation process. A high-k top-gate on the epitaxial graphene is ... More
Index theory of uniform pseudodifferential operatorsFeb 02 2015We generalize Roe's index theorem for graded generalized Dirac operators on amenable manifolds to multigraded elliptic uniform pseudodifferential operators. This generalization will follow as a corollary from a local index theorem that is valid on any ... More
Asymptotics of work distributions in non-equilibrium systemsJul 25 2008Aug 28 2009The asymptotic behaviour of the work probability distribution in driven non-equilibrium systems is determined using the method of optimal fluctuations. For systems described by Langevin dynamics the corresponding Euler-Lagrange equation together with ... More
Observation of Zitterbewegung in a spin-orbit coupled Bose-Einstein condensateJan 04 2013Aug 27 2013Spin-orbit coupled ultra-cold atoms provide an intriguing new avenue for the study of rich spin dynamics in superfluids. In this Letter, we observe Zitterbewegung, the simultaneous velocity (thus position) and spin oscillations, of neutral atoms between ... More
Spectral density of the Dirac operator in two-flavour QCDNov 24 2014We compute the spectral density of the (Hermitean) Dirac operator in Quantum Chromodynamics with two light degenerate quarks near the origin. We use CLS/ALPHA lattices generated with two flavours of O(a)-improved Wilson fermions corresponding to pseudoscalar ... More
Testing the Witten-Veneziano mechanism with the Yang-Mills gradient flow on the latticeOct 30 2014We present a precise computation of the topological charge distribution in the $SU(3)$ Yang-Mills theory. It is carried out on the lattice with high statistics Monte Carlo simulations by employing the clover discretization of the field strength tensor ... More
Near-IR/optical monitoring programme of the 'Arecibo sample of OH/IR stars'Oct 31 2006Nov 02 2006We performed a near-IR/optical monitoring programme from 1999 to 2005 in order to study the variability properties of the 'Arecibo sample of OH/IR stars' (periods, amplitudes, and colour variations). Here we describe this multi-wavelength long-term monitoring ... More
Replica mean-field theory for Levy spin-glassesJan 10 2007Infinite-range spin-glass models with Levy-distributed interactions show a freezing transition similar to disordered spin systems on finite connectivity random graphs. It is shown that despite diverging moments of the local field distribution this transition ... More
Nuclear Matrix Elements for Double-Beta DecayOct 31 2015Recent progress in nuclear-structure theory has been dramatic. I describe recent and future applications of ab initio calculations and the generator coordinate method to double-beta decay. I also briefly discuss the old and vexing problem of the renormalization ... More
Universality of electron distributions in high-energy air showers - description of Cherenkov light productionJun 29 2005Dec 22 2005The shower simulation code CORSIKA has been used to investigate the electron energy and angular distributions in high-energy showers. Based on the universality of both distributions, we develop an analytical description of Cherenkov light emission in ... More
Control of transversal instabilities in reaction-diffusion systemsJan 15 2015In two-dimensional reaction-diffusion systems, local curvature perturbations in the shape of traveling waves are typically damped out and disappear in the course of time. If, however, the inhibitor diffuses much faster than the activator, transversal ... More
Control of chemical wave propagationMar 13 2014Using the Schl\"{o}gl model as a paradigmatic example of a bistable reaction-diffusion system, we discuss some physically feasible options of open and closed loop spatio-temporal control of chemical wave propagation.
Localizing to submanifolds in uniformly finite homologyFeb 10 2016Given a non-compact Riemannian manifold M and a submanifold N of codimension q, we will construct under certain assumptions on both M and N a localization map in uniformly finite homology. Investigating the continuity of the localization map for certain ... More
Comment on "Invalidation of the Kelvin Force in Ferrofluids"Jan 24 2001It is shown that the experimental results reported in cond-mat/0010412 do not invalidate the well-known expression for the Kelvin force density in ferrofluids.
Correlation of internal representations in feed-forward neural networksApr 11 1996Feed-forward multilayer neural networks implementing random input-output mappings develop characteristic correlations between the activity of their hidden nodes which are important for the understanding of the storage and generalization performance of ... More
Approximate Treatment of Lepton Distortion in Charged-Current Neutrino Scattering from NucleiNov 21 1997The partial-wave expansion used to treat the distortion of scattered electrons by the nuclear Coulomb field is simpler and considerably less time-consuming when applied to the production of muons and electrons by low and intermediate-energy neutrinos. ... More
Very High Energy Cosmic Rays and Their InteractionsApr 15 2005The investigation of high energy cosmic rays and their interactions is a very active field of research. This article summarizes the progress made during the last years as reflected by the contributions to the XIII International Symposium on Very High ... More
A Proof of Looijenga's Conjecture via Integral-affine GeometrySep 26 2014A cusp singularity is an elliptic surface singularity whose minimal resolution is a cycle of smooth rational curves meeting transversely. Cusp singularities come in naturally dual pairs. In 1981, Looijenga proved that whenever a cusp singularity is smoothable, ... More
Stability and Convergence of Product Formulas for Operator MatricesJul 04 2012Aug 27 2012We present easy to verify conditions implying stability estimates for operator matrix splittings which ensure convergence of the associated Trotter, Strang and weighted product formulas. The results are applied to inhomogeneous abstract Cauchy problems ... More
Theory of Spin Hall Effects in SemiconductorsMar 10 2006May 23 2007Spin Hall effects are a collection of phenomena, resulting from spin-orbit coupling, in which an electrical current flowing through a sample can lead to spin transport in a perpendicular direction and spin accumulation at lateral boundaries. These effects, ... More
Theory of Spin Hall conductivity in n-doped GaAsMay 21 2005We develop a theory of extrinsic spin currents in semiconductors, resulting from spin-orbit coupling at charged scatterers, which leads to skew scattering and side jump contributions to the spin Hall conductance. Applying the theory to bulk n-GaAs, without ... More
Large deviations in Taylor dispersionNov 24 2016We establish a link between the phenomenon of Taylor dispersion and the theory of empirical distributions. Using this connection, we derive, upon applying the theory of large deviations, an alternative and much more precise description of the long-time ... More
The Gravitational Constant as a quantum mechanical expressionMar 08 2016A quantitatively verifiable expression for the Gravitational Constant is derived in terms of quantum mechanical quantities. This derivation appears to be possible by selecting a suitable physical process in which the transformation of the equation of ... More
Extensive Air Showers and Accelerator Data - The NEEDS WorkshopDec 23 2002Very high energy cosmic rays are typically studied by measuring extensive air showers formed by secondary particles produced in collisions with air nuclei. The indirect character of the measurement makes the physics interpretation of cosmic ray data strongly ... More
Implications of HERA results for very high energy cosmic ray physicsNov 13 1998Experimental results obtained with the HERA collider and recent progress in their theoretical interpretation are reviewed. After a short introduction to HERA physics, deep inelastic scattering and photoproduction are discussed as (virtual) photon-proton ... More
Soft interactions (presented at ISMD31)Nov 29 2001Dec 06 2001A brief introduction to the theory and phenomenology of soft interactions is given, focusing on total and elastic cross sections and multiparticle production.