Results for "Uwe Beckmann"

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Recent results on the helicity structure of the nucleon from HERMESOct 21 2002The HERMES experiment has measured double spin asymmetries of inclusive and semi-inclusive cross sections for the production of charged hadrons in deep-inelastic scattering of polarised positrons on polarised hydrogen and deuterium targets, in the kinematic ... More
Evolutionary behaviour of BL Lac objectsOct 09 1998We present analysis of a new flux limited sample of 72 X-ray selected BL Lacertae objects with known redshifts for 59 of them. We find the more X-ray dominated BL Lac having negative evolution with redshift, while intermediate objects show no evolution ... More
INTEGRAL - operating high-energy detectors for five years in spaceOct 23 2007The INTEGRAL satellite, which studies the Universe in the hard X-ray and soft Gamma-ray domain, has been operational for 5 years now. The X-ray telescopes, which use the coded mask technique, provide unprecedented spectral and imaging resolution. This ... More
The INTEGRAL Science Data CentreJun 28 2002The INTEGRAL Science Data Centre (ISDC) processes, archives and distributes data from the INTEGRAL mission. At the ISDC incoming data from the satellite are processed and searched for transient sources and Gamma-Ray bursts. The data are archived and distributed ... More
New results from the HRX BL Lac sampleJul 07 2000We present results for the Hamburg BL Lac sample, based on data provided by the RASS-BSC. By fitting a single power law to the X-ray data we find, in a number of objects, an additional absorbing component to the galactic value of NH, which might be attributed ... More
On the computational complexity of cut-reductionDec 10 2007Using appropriate notation systems for proofs, cut-reduction can often be rendered feasible on these notations, and explicit bounds can be given. Developing a suitable notation system for Bounded Arithmetic, and applying these bounds, all the known results ... More
Models of Disease SpectraJul 19 2012Case vs control comparisons have been the classical approach to the study of neurological diseases. However, most patients will not fall cleanly into either group. Instead, clinicians will typically find patients that cannot be classified as having clearly ... More
Wireless LAN techniques for mobile instrument controlOct 20 2002Oct 24 2002A choice of wireless technologies is available today. Not all of them are suitable to be used in a instrument control network at a neutron scattering facility. This paper will start with an overview of the wireless communication protocols IrDA, IEEE 802.11 ... More
Bayesian estimators of the Gamma distributionJul 12 2016In this paper we introduce two Bayesian estimators for learning the parameters of the Gamma distribution. The first algorithm uses a well known unnormalized conjugate prior for the Gamma shape and the second one uses a non-linear approximation to the ... More
Singular conformally invariant trilinear forms and generalized Rankin Cohen operatorsApr 18 2011The most singular residues of the standard meromorphic family of trilinear conformally invariant forms on $\mathcal C^\infty_c(\mathbb R^d)$ are computed. Their expression involves covariant bidifferential operators (generalized Rankin Cohen operators), ... More
Experimental Evidence for Crossed Andreev ReflectionDec 19 2005We report on electronic transport properties of mesoscopic superconductor-ferromagnet spin-valve structures. Two ferromagnetic iron leads form planar tunnel contacts to a superconducting aluminum wire, where the distance of the two contacts is of the ... More
Liaison classes of modulesSep 25 2004We propose a concept of module liaison that extends Gorenstein liaison of ideals and provides an equivalence relation among unmixed modules over a commutative Gorenstein ring. Analyzing the resulting equivalence classes we show that several results known ... More
Comparing Castelnuovo-Mumford regularity and extended degree: the borderline casesNov 28 2003Castelnuovo-Mumford regularity and any extended degree function can be thought of as complexity measures for the structure of finitely generated graded modules. A recent result of Doering, Gunston, Vasconcelos shows that both can be compared in case of ... More
Free Lévy Processes on Dual GroupsMar 23 2002We give a short introduction to the theory of L\'evy processes on dual groups. As examples we consider L\'evy processes with additive increments and L\'evy processes on the dual affine group.
An ensemble related to discrete orthogonal polynomials and its application to tilings of a half-hexagonJan 19 2011Jun 28 2013We discuss asymptotic properties of a family of discrete probability measures which may be used to model particle configurations with a wall on a set of discrete nodes. The correlations are shown to be determinantal and are expressed in terms of discrete ... More
Aperiodic crystals and beyondJun 17 2015Crystals are paradigms of ordered structures. While order was once seen as synonymous with lattice periodic arrangements, the discoveries of incommensurate crystals and quasicrystals led to a more general perception of crystalline order, encompassing ... More
Minimal free resolutions of projective subschemes of small degreeMay 16 2005We discuss the minimal free resolution of an irreducible projective subscheme X. If X is also reduced, we focus on the case when its degree equals two plus the codimension. The set of all possible graded Betti numbers is described if the codimension is ... More
Improved Sputter Depth Resolution in Auger Thin Film Analysis Using In Situ Low Angle Cross-SectionsFeb 17 2015A none conventional approach for depth profiling of thin film systems with enhanced depth resolution has been developed using standard Auger microprobe instruments. For the preparation of an in situ low angle cross-section, the sample is partly covered ... More
Siegel Modular Varieties and the Eisenstein Cohomology of $\PGL_{2g+1}$Feb 01 2013Mar 14 2013We use the twisted topological trace formula developed in an earlier paper to understand liftings from symplectic to general linear groups. We analyse the lift from $\SP_{2g}$ to $\PGL_{2g+1}$ over the ground field $\Q$ in further detail, and we get a ... More
On Undetected Redundancy in the Burrows-Wheeler TransformApr 05 2018The Burrows-Wheeler-Transform (BWT) is an invertible permutation of a text known to be highly compressible but also useful for sequence analysis, what makes the BWT highly attractive for lossless data compression. In this paper, we present a new technique ... More
Vacuum Quality Monitoring of Analytical Sputter Depth Profile Equipment by Recontamination Measurements of a Sputtered Ti SurfaceJan 01 2017Often a surface sensitive analytical technique in combination with sample erosion by inert ion sputtering is used for compositional in-depth analysis of solid state samples. Layer by layer the sample gets eroded and then the composition of the actual ... More
Orientations of 1-Factorizations and the List Chromatic Index of Small GraphsMay 01 2017As starting point, we formulate a corollary to the Quantitative Combinatorial Nullstellensatz. This corollary does not require the consideration of any coefficients of polynomials, only evaluations of polynomial functions. In certain situations, our corollary ... More
Volume Laws for Boxed Plane Partitions and Area Laws for Ferrers DiagramsApr 28 2008Jan 27 2009We asymptotically analyse the volume-random variables of general, symmetric and cyclically symmetric plane partitions fitting inside a box. We consider the respective symmetry class equipped with the uniform distribution. We also prove area limit laws ... More
Bench Measurements and Simulations of Beam Coupling ImpedanceMay 04 2018After a general introduction, the basic principles of wake-field and beamcoupling- impedance computations are explained. This includes time domain, frequency domain, and methods that do not include excitations by means of a particle beam. The second part ... More
Simple evaluation of one of Malmstén's integralsSep 25 2017The logarithmic integral no. 4.325.7 from Gradshteyn and Ryzhik's tables of integrals was first evaluated by Malmst\'en. Recently, Blagouchine used contour integration methods to evaluate a family of logarithmic integrals that contains this integral. ... More
Weights in arithmetic geometryMar 03 2010The concept of weights on the cohomology of algebraic varieties was initiated by fundamental ideas and work of A. Grothendieck and P. Deligne. It is deeply connected with the concept of motives and appeared first on the singular cohomology as the weights ... More
Determining the geometry of noncircular gears for given transmission functionMay 07 2019A pair of noncircular gears can be used to generate a strictly increasing continuous function $\psi(\varphi)$ whose derivative $\psi'(\varphi) = \mathrm{d}\psi(\varphi)/\mathrm{d}\varphi > 0$ is $2\pi/n$-periodic, where $\varphi$ and $\gamma = \psi(\varphi)$ ... More
Influence of the SIPG penalisation on the numerical properties of linear systems for elastic wave propagationDec 15 2017Interior penalty discontinuous Galerkin discretisations (IPDG) and especially the symmetric variant (SIPG) for time-domain wave propagation problems are broadly accepted and widely used due to their advantageous properties. Linear systems with block structure ... More
Kinematic Fitting in the Presence of ISR at the ILCJan 29 2009Kinematic fitting is a well-established tool to improve jet energy and invariant mass resolutions by fitting the measured values under constraints (e.g. energy conservation). However, in the presence of substantial ISR and Beamstrahlung, naive energy ... More
Void Statistics and Void Galaxies in the 2dFGRSOct 15 2007For the 2dFGRS we study the properties of voids and of fainter galaxies within voids that are defined by brighter galaxies. Our results are compared with simulated galaxy catalogues from the Millenium simulation coupled with a semianalytical galaxy formation ... More
INTEGRAL observations of the field of the BL Lacertae object S5~0716+714Aug 31 2004We have performed observations of the blazar S5 0716+714 with INTEGRAL on 2-6 April 2004. In the first months of 2004, the source had increased steadily in optical brightness and had undergone two outbursts. During the latter, occurred in March, it reached ... More
The variability of the quasar 3C 273: a radio to gamma-ray viewDec 11 2009We have analysed the first 15 months of Fermi/LAT data of the radio loud quasar 3C 273. Intense gamma-ray activity has been detected, showing an average flux of F(> 100 MeV) = 1.4e-6 ph/cm^2/s, with a peak at F(> 100 MeV) = 5.6e-6 ph/cm^2/s detected during ... More
The nature of the multi-wavelength emission of 3C 111Jul 13 2012Jul 31 2012We attempt to determine the nature of the high energy emission of the radio galaxy 3C 111, by distinguishing between the effects of the thermal and non-thermal processes. We study the X-ray spectrum of 3C 111 between 0.4 keV and 200 keV, and its spectral ... More
The extreme high frequency peaked BL Lac 1517+656Oct 25 1999We present optical spectroscopy data that allowed a measurement of the redshift for the X-ray selected BL Lacertae object 1517+656. With a redshift of z = 0.702 this object has an absolute magnitude of B = -26.4 and is also an extremely powerful radio ... More
Treatment of Photon Radiation in Kinematic Fits at Future e+ e- CollidersJun 02 2010Kinematic fitting, where constraints such as energy and momentum conservation are imposed on measured four-vectors of jets and leptons, is an important tool to improve the resolution in high-energy physics experiments. At future e+ e- colliders, photon ... More
X-ray luminous radio-quiet high redshift QSOs in the ROSAT All-Sky SurveyApr 19 1999X-ray luminous radio-quiet high redshift QSOs are rare and can be used for the investigation of several important astronomical questions. We have conducted a large area survey for radio-quiet high redshift QSOs in the ROSAT All-Sky Survey, from which ... More
Consideration of Photon Radiation in Kinematic Fits for Future e+ e- CollidersJun 30 2010Kinematic fitting is an important tool to improve the resolution in high-energy physics experiments. At future e+e- colliders, photon radiation parallel to the beam carrying away large amounts of energy and momentum will become a challenge for kinematic ... More
Fermi detected blazars seen by INTEGRALDec 11 2009Dec 14 2009Multiwavelength observations are essential to constrain physical parameters of the blazars observed by Fermi/LAT. Among the 187 AGN significantly detected in public INTEGRAL data above 20 keV by the imager IBIS/ISGRI, 20 blazars were detected. 15 of these ... More
On Reasoning with AmbiguitiesFeb 21 1995Feb 22 1995The paper adresses the problem of reasoning with ambiguities. Semantic representations are presented that leave scope relations between quantifiers and/or other operators unspecified. Truth conditions are provided for these representations and different ... More
Trigonometric R Matrices related to `Dilute' Birman--Wenzl--Murakami AlgebraFeb 16 1994Explicit expressions for three series of $R$ matrices which are related to a ``dilute'' generalisation of the Birman--Wenzl--Murakami are presented. Of those, one series is equivalent to the quantum $R$ matrices of the $D^{(2)}_{n+1}$ generalised Toda ... More
Non-degenerate curves with maximal Hartshorne-Rao moduleSep 21 2002Extending results for space curves we establish bounds for the cohomology of a non-degenerate curve in projective $n$-space. As a consequence, for any given $n$ we determine all possible pairs $(d, g)$ where $d$ is the degree and $g$ is the (arithmetic) ... More
Characterization of some projective subschemes by locally free resolutionsDec 16 2002A locally free resolution of a subscheme is by definition an exact sequence consisting of locally free sheaves (except the ideal sheaf) which has uniqueness properties like a free resolution. The purpose of this paper is to characterize certain locally ... More
SDLCQ and String/Field Theory CorrespondencesFeb 05 2001String/Field theory correspondences have been discussed heavily in recent years. Here, we describe a testing scenario involving a non-perturbative field theory calculation using the framework of supersymmetric discrete light-cone quantization (SDLCQ). ... More
Aperiodicity and Disorder - Does it Matter?Oct 25 2000The effects of an aperiodic order or a random disorder on phase transitions in statistical mechanics are discussed. A heuristic relevance criterion based on scaling arguments as well as specific results for Ising models with random disorder or certain ... More
X-Ray Scattering at FeCo(001) Surfaces and the Crossover between Ordinary and Normal TransitionsOct 21 1997In a recent experiment by Krimmel et al. [PRL 78, 3880 (1997)], the critical behavior of FeCo near a (001) surface was studied by x-ray scattering. Here the experimental data are reanalyzed, taking into account recent theoretical results on order-parameter ... More
Nurse Rostering with Genetic AlgorithmsMar 19 2010In recent years genetic algorithms have emerged as a useful tool for the heuristic solution of complex discrete optimisation problems. In particular there has been considerable interest in their use in tackling problems arising in the areas of scheduling ... More
Space-Time-Parallel Poroelasticity SimulationDec 20 2017The accurate, reliable and efficient numerical approximation of multi-physics processes in heterogeneous porous media with varying media coefficients that include fluid flow and structure interactions is of fundamental importance in energy, environmental, ... More
A Pyramidal Evolutionary Algorithm with Different Inter-Agent Partnering Strategies for Scheduling ProblemsJan 21 2008Mar 03 2008This paper combines the idea of a hierarchical distributed genetic algorithm with different inter-agent partnering strategies. Cascading clusters of sub-populations are built from bottom up, with higher-level sub-populations optimising larger parts of ... More
Sputter-Induced Cross-Contaminations in Analytical AES and XPS Instrumentation: Utilization of the effect for the In-situ Deposition of Ultrathin Functional LayersFeb 27 2013Cross contaminations are observed on sample surfaces by AES and XPS, if multiple samples are mounted on one sample holder and a neighbouring sample was sputter depth profiled. During sputter depth profiling sputtered material is deposited on inner surfaces ... More
Thin film evolution equations from (evaporating) dewetting liquid layers to epitaxial growthOct 14 2010In the present contribution we review basic mathematical results for three physical systems involving self-organising solid or liquid films at solid surfaces. The films may undergo a structuring process by dewetting, evaporation/condensation or epitaxial ... More
Towards finding the single-particle content of two-dimensional adjoint QCDJun 26 2015The single-particle content of two-dimensional adjoint QCD remains elusive due to the inability to distinguish single- from multi-particle states. To find a criterion we compare several approximations to the theory. Starting from the asymptotic theory ... More
In-Situ Low-Angle Cross Sectioning: Bevel Slope Flattening due to Self-Alignment EffectsJun 24 2015Low-angle cross sections are produced inside an Auger microprobe using the equipped depth profile ion sputter gun. Simply the sample is partly covered by a mask. Utilizing the edge of this mask the sample is sputtered with ions. Due to the shading of ... More
Buffon's problem with a pivot needleJan 14 2014Jan 16 2014In this paper, we solve Buffon's needle problem for a needle consisting of two line segments connected in a pivot point.
Buffon's problem with a star of needles and a lattice of parallelogramsSep 24 2012A star of n (n greater than or equal to 2) line segments (needles) of equal length with common endpoint and constant angular spacing is randomly placed onto a lattice which is the union of two families of equidistant lines in the plane with angle alpha ... More
Hasse principles for higher-dimensional fieldsOct 15 2009Dec 04 2014For schemes X over global or local fields, or over their rings of integers, K. Kato stated several conjectures on certain complexes of Gersten-Bloch-Ogus type, generalizing the fundamental exact sequence of Brauer groups for a global field. He proved ... More
The mean width of the oloid and integral geometric applications of itApr 25 2016The oloid is the convex hull of two circles with equal radius in perpendicular planes so that the center of each circle lies on the other circle. We calculate the mean width of the oloid in two ways, first via the integral of mean curvature, and then ... More
Limit laws for discrete excursions and meanders and linear functional equations with a catalytic variableMay 26 2011Dec 13 2011We study limit distributions for random variables defined in terms of coefficients of a power series which is determined by a certain linear functional equation. Our technique combines the method of moments with the kernel method of algebraic combinatorics. ... More
On Dirichlet Products Evaluated at Fibonacci NumbersJun 06 2016In this work we discuss Dirichlet products evaluated at Fibonacci numbers. As first applications of the results we get a representation of Fibonacci numbers in terms of Euler's totient function, an upper bound on the number of primitive prime divisors ... More
Dilute Birman--Wenzl--Murakami Algebra and $D^{(2)}_{n+1}$ modelsFeb 14 1994A ``dilute'' generalisation of the Birman--Wenzl--Murakami algebra is considered. It can be ``Baxterised'' to a solution of the Yang--Baxter algebra. The $D^{(2)}_{n+1}$ vertex models are examples of corresponding solvable lattice models and can be regarded ... More
The roughening transition of interfaces in disordered mediaOct 29 1997Competing pinning effects on a D-dimensional interface by weak impurity disorder and a periodic potential of the underlying crystal lattice are analyzed for $2<D<4$. We use both the Gaussian variational method (GVM) and the functional renormalization ... More
On Cloning Context-FreenessJul 22 1997To Rogers (1994) we owe the insight that monadic second order predicate logic with multiple successors (MSO) is well suited in many respects as a realistic formal base for syntactic theorizing. However, the agreeable formal properties of this logic come ... More
Correlators in N=1 SYM(2+1)Apr 30 2001We present a calculation of the correlator <0|T^{++}(r) T^{++}(0) |0> in N=1 SYM theory in 2+1 dimensions. In the calculation, we use supersymmetric discrete light-cone quantization (SDLCQ), which preserves the supersymmetry at every step of the calculation. ... More
On the Role of the Annihilation Channel in Front Form PositroniumMay 12 1997The annihilation channel is implemented into the front form calculations of the positronium spectrum presented in a previous publication. The effective Hamiltonian is calculated analytically. Its eigensolutions are obtained numerically. A complete separation ... More
Level-spacing distributions of the Gaussian unitary random matrix ensembleNov 14 2002Jun 24 2004Level-spacing distributions of the Gaussian Unitary Ensemble (GUE) of random matrix theory are expressed in terms of solutions of coupled differential equations. Series solutions up to order 50 in the level spacing are obtained, thus providing a very ... More
Co-Indexing Labelled DRSs to Represent and Reason with AmbiguitiesJul 25 1995The paper addresses the problem of representing ambiguities in a way that allows for monotonic disambiguation and for direct deductive computation. The paper focuses on an extension of the formalism of underspecified DRSs to ambiguities introduced by ... More
A short-key one-time pad cipherAug 18 2016A process for the secure transmission of data is presented that has to a certain degree the advantages of the one-time pad (OTP) cipher, that is, simplicity, speed, and information-theoretically security, but overcomes its fundamental weakness, the necessity ... More
Recent advances in and future challenges for mesoscopic hydrodynamic modelling of complex wettingMar 14 2018Jul 21 2018We highlight some recent developments that widen the scope and reach of mesoscopic thin-film (or long-wave) hydrodynamic models employed to describe the dynamics of thin films, drops and contact lines of simple and complex liquids on solid substrates. ... More
Long Time Stability of the Energy Scale Calibration of a Quantum 2000Jun 10 2015According to the international standard ISO 15472 the energy scale of an XPS instrument, type Physical Electronics Quantum 2000, was calibrated. It is shown, how the procedures of the ISO 15472 were adapted to the hardware and software design of the Quantum ... More
Patterned deposition at moving contact linesJul 03 2013When a simple or complex liquid recedes from a smooth solid substrate it often leaves a homogeneous or structured deposit behind. In the case of a receding non-volatile pure liquid the deposit might be a liquid film or an arrangement of droplets depending ... More
Dienstplanerstellung in Krankenhaeusern mittels genetischer AlgorithmenMay 30 2013This thesis investigates the use of problem-specific knowledge to enhance a genetic algorithm approach to multiple-choice optimisation problems. It shows that such information can significantly enhance performance, but that the choice of information and ... More
Reducing the Aspect Ratio of Contact Holes by In-Situ Low-Angle Cross SectioningApr 16 2015Auger analysis of high-aspect ratio contact holes of integrated microelectronic devices is a challenging analytical task. Due to geometrical shadowing the primary electron beam and the energy analyser have not the required direct line of sight to the ... More
Rigidity theorems for K- and H-cohomology and other functorsMar 30 2015Apr 26 2018Suslin proved that for an extension K/k of algebraically closed fields the induced maps K_m(k)[n] --> K_m(K)[n] and K_m(k)/n ---> K_m(K)/n for the higher K-groups are isomorphisms, where A[n] is the subgroup of n-torsion in an abelien group, and A/n = ... More
An Indirect Genetic Algorithm for Set Covering ProblemsMar 20 2008This paper presents a new type of genetic algorithm for the set covering problem. It differs from previous evolutionary approaches first because it is an indirect algorithm, i.e. the actual solutions are found by an external decoder function. The genetic ... More
Artificial Immune Systems (AIS) - A New Paradigm for Heuristic Decision MakingJan 28 2008May 16 2008Over the last few years, more and more heuristic decision making techniques have been inspired by nature, e.g. evolutionary algorithms, ant colony optimisation and simulated annealing. More recently, a novel computational intelligence technique inspired ... More
Multiplicative monotone convolutionsMar 25 2005Recently, Bercovici has introduced multiplicative convolutions based on Muraki's monotone independence and shown that these convolution of probability measures correspond to the composition of some function of their Cauchy transforms. We provide a new ... More
Deformation of string topology into homotopy skein modulesNov 25 2002Oct 20 2003Relations between the string topology of Chas and Sullivan and the homotopy skein modules of Hoste and Przytycki are studied. This provides new insight into the structure of homotopy skein modules and their meaning in the framework of quantum topology. ... More
Quantum deformations of fundamental groups of oriented 3-manifoldsFeb 27 2002Feb 27 2002We compute two-term skein modules of framed oriented links in oriented 3-manifolds. They contain the self-writhe and total linking number invariants of framed oriented links in a universal way. The relations in a natural presentation of the skein module ... More
Measures and geometric probabilities for ellipses intersecting circlesDec 06 2016Santal\'o calculated the measures for all positions of a moving line segment in which it lies inside a fixed circle and intersects this circle in one or two points. From these measures he concluded hitting probabilities for a line segment thrown randomly ... More
Hitting probabilities for random convex bodies and lattices of trianglesDec 18 2013In the first part of this paper, we obtain symmetric formulae for the probabilities that a plane convex body hits exactly 1, 2, 3, 4, 5 or 6 triangles of a lattice of congruent triangles in the plane. Furthermore, a very simple formula for the expectation ... More
Random chords and point distances in regular polygonsApr 12 2012Sep 05 2012In this paper we obtain the chord length distribution function for any regular polygon. From this function we conclude the density function and the distribution function of the distance between two uniformly and independently distributed random points ... More
Technical Report: Artificial DNA - a Concept for Self-Building Embedded SystemsJul 24 2017This technical report deals with the concept of an artificial DNA which contains a blueprint of the structure and organization of an embedded system. This blueprint can be used to build up the embedded system in a self-organizing manner at run-time. The ... More
Dilute Algebras and Solvable Lattice ModelsNov 24 1995The definition of a dilute braid-monoid algebra is briefly reviewed. The construction of solvable vertex and interaction-round-a-face models built on representations of the dilute Temperley-Lieb and Birman-Wenzl-Murakami algebras is discussed.
Representations of Two-Colour BWM Algebras and Solvable Lattice ModelsDec 03 1996Many of the known solutions of the Yang-Baxter equation, which are related to solvable lattice models of vertex- and IRF-type, yield representations of the Birman-Wenzl-Murakami algebra. From these, representations of a two-colour generalization of the ... More
Note on a Positronium Model from Flow Equations in Front Form DynamicsAug 13 1998Jan 16 2001In this note we address the problem of solving for the positronium mass spectrum. We use front-form dynamics together with the method of flow equations. For a special choice of the similarity function, the calculations can be simplified by analytically ... More
SYM Correlators and the Maldacena ConjectureAug 21 2002We report on progress in evaluating quantum filed theories with supersymmetric discrete light-cone quantization (SDLCQ). We compare the method to lattice gauge theory and point out its relevance for lattice calculations. As an exciting application we ... More
Analytical solution to the Schrodinger equation of a laser-driven correlated two-particle systemJan 31 2002The time-dependent quantum system of two laser-driven electrons in a harmonic oscillator potential is analysed, taking into account the repulsive Coulomb interaction between both particles. The Schrodinger equation of the two-particle system is shown ... More
Improved bounds on the number of ternary square-free wordsMay 29 2001Aug 02 2001Improved upper and lower bounds on the number of square-free ternary words are obtained. The upper bound is based on the enumeration of square-free ternary words up to length 110. The lower bound is derived by constructing generalised Brinkhuis triples. ... More
Testing SDLCQ in 2+1 dimensionsMar 13 2000The SDLCQ regularization is known to explicitly preserve supersymmetry in 1+1 dimensions. To test this property in higher dimensions, we consider supersymmetric Yang-Mills theory on R x S^1 x S^1. In particular, we choose one of the compact directions ... More
Basis Invariants in Non--Abelian Gauge TheoriesJan 23 1997Feb 05 1997A basis of Lorentz and gauge-invariant monomials in non--Abelian gauge theories with matter is described, applicable for the inverse mass expansion of effective actions. An algorithm to convert an arbitrarily given invariant expression into a linear combination ... More
Recent HERA Results and Future ProspectsJun 10 1998A few selected HERA results are presented and the prospects for future measurements with high luminosity are discussed, which will become available after the planned luminosity upgrade of the HERA storage ring planned for 2000.
Kinetic Model for Stochastic Heating in the INCA DischargeJun 01 2018Jun 07 2018A novel electron heating mechanism based on periodically structured vortex fields induced in a plane was first proposed in 2014 [U. Czarnetzki and Kh. Tarnev, Physics of Plasmas 21, 123508 (2014)]. This theoretical concept has now been realized in an ... More
On a harmonic solution for two-dimensional adjoint QCDMay 31 2018Two-dimensional QCD with adjoint fermions has many attractive features, yet its single-particle content remains largely unknown. To lay the foundation for a crucially improved approximation of the theory's spectrum, we developed a method to find the basis ... More
Application of the analytical methods REM/EDX, AES and SNMS to a chlorine induced aluminium corrosionFeb 06 2015Scanning electron microscopy - SEM - with energy dispersive X-ray detection - EDX -, Auger electron spectroscopy - AES - and sputtered neutral mass spectrometry - SNMS - have been used to characterize a chlorine induced corrosion of an aluminium metallisation. ... More
Genetic Algorithms for Multiple-Choice ProblemsApr 19 2010This thesis investigates the use of problem-specific knowledge to enhance a genetic algorithm approach to multiple-choice optimisation problems.It shows that such information can significantly enhance performance, but that the choice of information and ... More
On Stronger Calculi for QBFsApr 21 2016Quantified Boolean formulas (QBFs) generalize propositional formulas by admitting quantifications over propositional variables. QBFs can be viewed as (restricted) formulas of first-order predicate logic and easy translations of QBFs into first-order formulas ... More
On the depinning of a drop of partially wetting liquid on a rotating cylinderOct 14 2010We discuss the analogy of the behaviour of films and drops of liquid on a rotating horizontal cylinder on the one hand and substrates with regular one-dimensional wettability patterns on the other hand. Based on the similarity between the respective governing ... More
Analysis of a Sputtered Si Surface for Ar Sputter Gas Supply Purity MonitoringApr 10 2017For sputter depth profiling often sample erosion by Ar+ ions is used. Only a high purity of the sputter gas and a low contamination level of the ion gun avoids misleading depth profile measurements results. Here a new measurement procedure is presented, ... More
Frobenius algebras and skein modules of surfaces in 3-manifoldsFeb 27 2008For each Frobenius algebra there is defined a skein module of surfaces embedded in a given 3-manifold and bounding a prescribed curve system in the boundary. The skein relations are local and generate the kernel of a certain natural extension of the corresponding ... More
Empty simplices of polytopes and graded Betti numbersDec 14 2005The conjecture of Kalai, Kleinschmidt, and Lee on the number of empty simplices of a simplicial polytope is established by relating it to the first graded Betti numbers of the polytope. The proof allows us to derive explicit optimal bounds on the number ... More
Killing forms on G2 and Spin7 manifoldsOct 04 2004Killing forms on Riemannian manifolds are differential forms whose covariant derivative is totally skew-symmetric. We show that on a compact manifold with holonomy G2 or Spin7 any Killing form has to be parallel. The main tool is a universal Weitzenboeck ... More