Results for "Stefan Sorge"

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On Kernelization and Approximation for the Vector Connectivity ProblemOct 31 2014Jun 23 2015In the Vector Connectivity problem we are given an undirected graph $G=(V,E)$, a demand function $\phi\colon V\to\{0,\ldots,d\}$, and an integer $k$. The question is whether there exists a set $S$ of at most $k$ vertices such that every vertex $v\in V\setminus ... More
The Minimum Feasible Tileset problemSep 30 2014We consider the Minimum Feasible Tileset problem: Given a set of symbols and subsets of these symbols (scenarios), find a smallest possible number of pairs of symbols (tiles) such that each scenario can be formed by selecting at most one symbol from each ... More
Smoothing of the slowly extracted coasting beam from a synchrotronApr 19 2019Slow extraction of beam from synchrotrons or storage rings as required by many fixed target experiments is performed by controlled excitation and feeding of a structural lattice resonance. Due to the sensitive nature of this resonant extraction process, ... More
The Parameterized Complexity of the Minimum Shared Edges ProblemFeb 04 2016We study the NP-complete Minimum Shared Edges (MSE) problem. Given an undirected graph, a source and a sink vertex, and two integers p and k, the question is whether there are p paths in the graph connecting the source with the sink and sharing at most ... More
On Computing Centroids According to the $p$-Norms of Hamming Distance VectorsJul 17 2018Jun 26 2019In this paper we consider the $p$-Norm Hamming Centroid problem which asks to determine whether some given binary strings have a centroid with a bound on the $p$-norm of its Hamming distances to the strings. Specifically, given a set of strings $S$ and ... More
Matchings under Preferences: Strength of Stability and Trade-offsFeb 15 2019Jun 05 2019We propose two solution concepts for matchings under preferences: robustness and near stability. The former strengthens while the latter relaxes the classic definition of stability by Gale and Shapley (1962). Informally speaking, robustness requires that ... More
A Note on Clustering AggregationJul 24 2018We consider the clustering aggregation problem in which we are given a set of clusterings and want to find an aggregated clustering which minimizes the sum of mismatches to the input clusterings. In the binary case (each clustering is a bipartition) this ... More
On Computing Centroids According to the $p$-Norms of Hamming Distance VectorsJul 17 2018Jul 18 2018In this paper we consider the \textsc{$p$-Norm Hamming Centroid} problem which asks to determine whether some given binary strings have a centroid with a bound on the $p$\nobreakdash-norm of its Hamming distances to the strings. Specifically, given a ... More
Valuation of path-dependent American options using a Monte Carlo approachJan 12 1998It is shown how to obtain accurate values for American options using Monte Carlo simulation. The main feature of the novel algorithm consists of tracking the boundary between exercise and hold regions via optimization of a certain payoff function. We ... More
Collective flow and QCD phase transitionJun 16 1999Jun 23 1999In the first part I discuss the sensitivity of collective matter expansion in ultrarelativistic heavy-ion collisions to the transition between quark and hadronic matter (physics of the softest point of the Equation of State). A kink in the centrality ... More
Constant-factor approximations for Capacitated Arc Routing without triangle inequalityApr 14 2014Given an undirected graph with edge costs and edge demands, the Capacitated Arc Routing problem (CARP) asks for minimum-cost routes for equal-capacity vehicles so as to satisfy all demands. Constant-factor polynomial-time approximation algorithms were ... More
``Day 1'' Physics at RHIC: Predictions from RQMDMay 04 1999I discuss predictions based on the transport theoretical approach ``relativistic quantum molecular dynamics''. They can be tested rather soon by the upcoming experiments at the Relativistic Heavy Ion Collider at BNL (RHIC). Here I focus on the question ... More
Assessing the Computational Complexity of Multi-Layer Subgraph DetectionApr 26 2016Multi-layer graphs consist of several graphs (layers) over the same vertex set. They are motivated by real-world problems where entities (vertices) are associated via multiple types of relationships (edges in different layers). We chart the border of ... More
Highly Sensitive Centrality Dependence of Elliptic Flow -- A Novel Signature of the Phase Transition in QCDDec 21 1998Jun 24 1999Elliptic flow of the hot, dense system which has been created in nucleus-nucleus collisions develops as a response to the initial azimuthal asymmetry of the reaction region. Here it is suggested that the magnitude of this response shows a ``kinky'' dependence ... More
Solving Partition Problems Almost Always Requires Pushing Many Vertices AroundAug 27 2018A fundamental graph problem is to recognize whether the vertex set of a graph G can be bipartitioned into sets A and B such that G[A] and G[B] satisfy properties P_A and P_B, respectively. This so-called (P_A,P_B)-RECOGNITION problem generalizes amongst ... More
Your Rugby Mates Don't Need to Know your Colleagues: Triadic Closure with Edge ColorsNov 23 2018Given an undirected graph $G=(V,E)$ the NP-hard Strong Triadic Closure (STC) problem asks for a labeling of the edges as weak and strong such that at most $k$ edges are weak and for each induced $P_3$ in $G$ at least one edge is weak. In this work, we ... More
Packing directed circuits quarter-integrallyJul 04 2019The celebrated Erd\H{o}s-P\'{o}sa theorem states that every undirected graph that does not admit a family of $k$ vertex-disjoint cycles contains a feedback vertex set (a set of vertices hitting all cycles in the graph) of size $O(k \log k)$. After being ... More
Efficient Algorithms for Measuring the Funnel-likeness of DAGsJan 31 2018Funnels are a new natural subclass of DAGs. Intuitively, a DAG is a funnel if every source-sink path can be uniquely identified by one of its arcs. Funnels are an analog to trees for directed graphs that is more restrictive than DAGs but more expressive ... More
Remnants of Initial Anisotropic High Energy Density Domains in Nucleus-Nucleus CollisionsNov 03 1998Dec 19 1998Anisotropic high energy density domains may be formed at early stages of ultrarelativistic heavy ion collisions, e.g. due to phase transition dynamics or non-equilibrium phenomena like (mini-)jets. Here we investigate hadronic observables resulting from ... More
The Minimum Shared Edges Problem on Planar GraphsFeb 03 2016We study the Minimum Shared Edges problem introduced by Omran et al. [Journal of Combinatorial Optimization, 2015] on planar graphs: Planar MSE asks, given a planar graph G = (V,E), two distinct vertices s,t in V , and two integers p, k, whether there ... More
Computational Complexity Aspects of Point Visibility GraphsNov 06 2017May 16 2018A point visibility graph is a graph induced by a set of points in the plane where the vertices of the graph represent the points in the point set and two vertices are adjacent if and only if no other point from the point set lies on the line segment between ... More
Resource Adaptive Agents in Interactive Theorem ProvingJan 23 2009We introduce a resource adaptive agent mechanism which supports the user in interactive theorem proving. The mechanism uses a two layered architecture of agent societies to suggest appropriate commands together with possible command argument instantiations. ... More
sec-cs: Getting the Most out of Untrusted Cloud StorageJun 10 2016We present sec-cs, a hash-table-like data structure for file contents on untrusted storage that is both secure and storage-efficient. We achieve authenticity and confidentiality with zero storage overhead using deterministic authenticated encryption. ... More
Reliability of regulatory networks and its evolutionMay 27 2008The problem of reliability of the dynamics in biological regulatory networks is studied in the framework of a generalized Boolean network model with continuous timing and noise. Using well-known artificial genetic networks such as the repressilator, we ... More
Reliability of genetic networks is evolvableJul 10 2007Control of the living cell functions with remarkable reliability despite the stochastic nature of the underlying molecular networks -- a property presumably optimized by biological evolution. We here ask to what extent the property of a stochastic dynamical ... More
The midpoint between dipole and parton showersJun 16 2015Sep 19 2015We present a new parton-shower algorithm. Borrowing from the basic ideas of dipole cascades, the evolution variable is judiciously chosen as the transverse momentum in the soft limit. This leads to a very simple analytic structure of the evolution. A ... More
Interactive Natural Language Acquisition in a Multi-modal Recurrent Neural ArchitectureMar 24 2017Feb 07 2018For the complex human brain that enables us to communicate in natural language, we gathered good understandings of principles underlying language acquisition and processing, knowledge about socio-cultural conditions, and insights about activity patterns ... More
Stochastic mortality models: An infinite dimensional approachJul 11 2019Demographic projections of future mortality rates involve a high level of uncertainty and require stochastic mortality models. The current paper investigates forward mortality models driven by a (possibly infinite dimensional) Wiener process and a compensated ... More
Weak Limit of the 3-State Quantum Walk on the LineApr 04 2014May 21 2014We revisit the one dimensional discrete time quantum walk with 3 states and the Grover coin. We derive analytic expressions for observed the localization, an long time approximation for the probability density function (PDF). We also connect the time ... More
Streaming KernelizationMay 06 2014Kernelization is a formalization of preprocessing for combinatorially hard problems. We modify the standard definition for kernelization, which allows any polynomial-time algorithm for the preprocessing, by requiring instead that the preprocessing runs ... More
On the commutability of homogenization and linearization in finite elasticityNov 16 2010May 16 2011We study non-convex elastic energy functionals associated to (spatially) periodic, frame indifferent energy densities with a single non-degenerate energy well at SO(n). Under the assumption that the energy density admits a quadratic Taylor expansion at ... More
Evidence of early multi-strange hadron freeze-out in high energy nuclear collisionsApr 18 1998Recently reported transverse momentum distributions of strange hadrons produced in Pb(158AGeV) on Pb collisions and corresponding results from the relativistic quantum molecular dynamics (RQMD) approach are examined. We argue that the experimental observations ... More
The H-Covariant Strong Picard GroupoidSep 08 2004Apr 25 2005The notion of H-covariant strong Morita equivalence is introduced for *-algebras over C = R(i) with an ordered ring R which are equipped with a *-action of a Hopf *-algebra H. This defines a corresponding H-covariant strong Picard groupoid which encodes ... More
A shortcut to (sun)flowers: Kernels in logarithmic space or linear timeApr 30 2015We investigate whether kernelization results can be obtained if we restrict kernelization algorithms to run in logarithmic space. This restriction for kernelization is motivated by the question of what results are attainable for preprocessing via simple ... More
Finite-Size Corrections for Ground States of Edwards-Anderson Spin GlassesOct 28 2011May 30 2012Extensive computations of ground state energies of the Edwards-Anderson spin glass on bond-diluted, hypercubic lattices are conducted in dimensions d=3,..,7. Results are presented for bond-densities exactly at the percolation threshold, p=p_c, and deep ... More
Superstability of the yeast cell cycle dynamics: Ensuring causality in the presence of biochemical stochasticityMay 05 2006Gene regulatory dynamics is governed by molecular processes and therefore exhibits an inherent stochasticity. However, for the survival of an organism it is a strict necessity that this intrinsic noise does not prevent robust functioning of the system. ... More
The generating of Fractal Images Using MathCAD ProgramMar 24 2009This paper presents the graphic representation in the z-plane of the first three iterations of the algorithm that generates the Sierpinski Gasket. It analyzes the influence of the f(z) map when we represent fractal images.
Projection methods for ill-posed problems revisitedJul 13 2015The discretization of least-squares problems for linear ill-posed operator equations in Hilbert spaces is considered. The main subject of this article concerns conditions for convergence of the associated discretized minimum-norm least-squares solution ... More
Twisted Reidemeister torsion, the Thurston norm and fibered manifoldsJan 29 2013We prove that the twisted Reidemeister torsion of a 3-manifold corresponding to a fibered class is monic and we show that it gives lower bounds on the Thurston norm. The former fixes a flawed proof in [FV10], the latter gives a quick alternative argument ... More
Reidemeister torsion, the Thurston norm and Harvey's invariantsAug 31 2005Feb 25 2006Recently twisted and higher order Alexander polynomials were used by Cochran, Harvey, Friedl--Kim and Turaev to give lower bounds on the Thurston norm. We first show how Reidemeister torsion relates to these Alexander polynomials. We then give lower bounds ... More
A Hidden Signal in the Ulam sequenceJul 01 2015Jul 06 2016The Ulam sequence is defined as $a_1 =1, a_2 = 2$ and $a_n$ being the smallest integer that can be written as the sum of two distinct earlier elements in a unique way. This gives $$1, 2, 3, 4, 6, 8, 11, 13, 16, 18, 26, 28, 36, 38, 47, \dots$$ Ulam remarked ... More
New Bounds for the Traveling Salesman ConstantNov 25 2013Mar 27 2014Let $X_1, X_2, \dots, X_n$ be independent and uniformly distributed random variables in the unit square $[0,1]^2$ and let $L(X_1, \dots, X_n)$ be the length of the shortest traveling salesman path through these points. In 1959, Beardwood, Halton $\&$ ... More
Nonextensive statistical mechanics and complex scale-free networksSep 07 2006One explanation for the impressive recent boom in network theory might be that it provides a promising tool for an understanding of complex systems. Network theory is mainly focusing on discrete large-scale topological structures rather than on microscopic ... More
Aging Exponents in Self-Organized CriticalityJun 11 1997Aug 07 1997In a recent Letter [Phys. Rev. Lett. 79, 889 (1997) and cond-mat/9702054] we have demonstrated that the avalanches in the Bak-Sneppen model display aging behavior similar to glassy systems. Numerical results for temporal correlations show a broad distribution ... More
Stiffness of the Edwards-Anderson Model in all DimensionsAug 01 2005Sep 23 2005A comprehensive description in all dimensions is provided for the scaling exponent $y$ of low-energy excitations in the Ising spin glass introduced by Edwards and Anderson. A combination of extensive numerical as well as theoretical results suggest that ... More
Neutron skin thickness of heavy nuclei with $α$-particle correlations and the slope of the nuclear symmetry energyMar 12 2014Jun 16 2014The formation of $\alpha$-particle clusters on the surface of heavy nuclei is described in a generalized relativistic mean-field model with explicit cluster degrees of freedom. The effects on the size of the neutron skin of Sn nuclei and ${}^{208}$Pb ... More
Fermions and the scattering equationsDec 18 2014Mar 03 2015This paper investigates how tree-level amplitudes with massless quarks, gluons and/or massless scalars transforming under a single copy of the gauge group can be expressed in the context of the scattering equations as a sum over the inequivalent solutions ... More
The SISCone jet algorithm optimised for low particle multiplicitiesAug 09 2011Dec 10 2011The SISCone jet algorithm is a seedless infrared-safe cone jet algorithm. There exists an implementation which is highly optimised for a large number of final state particles. However, in fixed-order perturbative calculations with a small number of final ... More
Does one need the O(epsilon)- and O(epsilon^2)-terms of one-loop amplitudes in an NNLO calculation ?Jul 26 2011Sep 12 2011This article discusses the occurences of one-loop amplitudes within a next-to-next-to-leading order calculation. In an NNLO calculation the one-loop amplitude enters squared and one would therefore naively expect that the O(epsilon)- and O(epsilon^2)-terms ... More
Automated calculations for multi-leg processesJul 23 2007Jul 26 2007The search for signals of new physics at the forthcoming LHC experiments involves the analysis of final states characterised by a high number of hadronic jets or identified particles. Precise theoretical predictions for these processes require the computation ... More
Hopf algebra structures in particle physicsOct 14 2003In the recent years, Hopf algebras have been introduced to describe certain combinatorial properties of quantum field theories. I will give a basic introduction to these algebras and review some occurrences in particle physics.
Moments of event shapes in electron-positron annihilation at NNLOSep 28 2009Nov 10 2009This article gives the perturbative NNLO results for the moments of the most commonly used event shape variables associated to three-jet events in electron-positron annihilation: Thrust, heavy jet mass, wide jet broadening, total jet broadening, C parameter ... More
Introduction to Monte Carlo methodsJun 23 2000These lectures given to graduate students in high energy physics, provide an introduction to Monte Carlo methods. After an overview of classical numerical quadrature rules, Monte Carlo integration together with variance-reducing techniques is introduced. ... More
Calculational techniques (not only) for single top productionMay 29 2000A next-to-leading order calculation for single top production including spin-dependent observables requires efficient techniques for the calculation of the relevant loop amplitudes. We discuss the adaption of dimensional regularization, the spinor helicity ... More
Coherent states and geodesics: cut locus and conjugate locusFeb 22 1995Sep 15 1995The intimate relationship between coherent states and geodesics is pointed out. For homogenous manifolds on which the exponential from the Lie algebra to the Lie group equals the geodesic exponential, and in particular for symmetric spaces, it is proved ... More
Symmetry Dependence of Localization in Quasi- 1- dimensional Disordered WiresMar 26 2000Jun 25 2000The crossover in energy level statistics of a quasi-1-dimensional disordered wire as a function of its length L is used, in order to derive its averaged localization length, without magnetic field, in a magnetic field and for moderate spin orbit scattering ... More
Indirect Detection of Dark Matter with gamma raysOct 10 2013Feb 12 2014The details of what constitutes the majority of the mass that makes up dark matter in the Universe remains one of the prime puzzles of cosmology and particle physics today - eighty years after the first observational indications. Today, it is widely accepted ... More
Status of the NLO Corrections to the Photon Impact FactorJun 20 2002We present the status of the programme of calculating the next-to-leading order corrections to the virtual photon impact factor. In particular, we discuss new results for the transversely polarized photon. We briefly outline the definition of infrared ... More
Herwig++ for e+e- collisionsAug 03 2004Some results obtained with the new Monte Carlo event generator Herwig++ are presented. In its first version (1.0), Herwig++ is capable of simulating e+e- Annihilation events. We discuss its relevance for future e+e- colliders and show results on the multiplicity ... More
From Unified Theories to Precision Neutrino ExperimentsAug 31 2006The expected high sensitivities of future neutrino oscillation experiments will allow precision tests of unified theories of flavour. In order to compare GUT scale predictions for neutrino masses, leptonic mixing angles and CP violating phases with experimental ... More
On Polynomial Kernels for Integer Linear Programs: Covering, Packing and FeasibilityFeb 14 2013Feb 15 2013We study the existence of polynomial kernels for the problem of deciding feasibility of integer linear programs (ILPs), and for finding good solutions for covering and packing ILPs. Our main results are as follows: First, we show that the ILP Feasibility ... More
On Polynomial Kernels for Sparse Integer Linear ProgramsFeb 14 2013Feb 15 2013Integer linear programs (ILPs) are a widely applied framework for dealing with combinatorial problems that arise in practice. It is known, e.g., by the success of CPLEX, that preprocessing and simplification can greatly speed up the process of optimizing ... More
Polynomial Kernelizations for MIN F^+Pi_1 and MAX NPFeb 11 2009Dec 13 2011It has been observed in many places that constant-factor approximable problems often admit polynomial or even linear problem kernels for their decision versions, e.g., Vertex Cover, Feedback Vertex Set, and Triangle Packing. While there exist examples ... More
The asymptotic rank of metric spacesJan 08 2007Oct 20 2008In this article we define and study a notion of asymptotic rank for metric spaces and show in our main theorem that for a large class of spaces, the asymptotic rank is characterized by the growth of the higher filling functions. For a proper, cocompact, ... More
Nilpotent groups without exactly polynomial Dehn functionApr 16 2010We prove super-quadratic lower bounds for the growth of the filling area function of a certain class of Carnot groups. This class contains groups for which it is known that their Dehn function grows no faster than $n^2\log n$. We therefore obtain the ... More
Measurement of the production cross section for W- and Z-bosons in association with jets in ATLASJun 10 2011We report on the measurements of inclusive W+jets and Z+jets cross sections in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector. Cross sections, in both the electron and muon decay modes of the bosons, are presented as a function of ... More
Theta divisors with curve summands and the Schottky problemSep 10 2014Aug 25 2015We prove the following converse of Riemann's Theorem: let (A,\Theta) be an indecomposable principally polarized abelian variety whose theta divisor can be written as a sum of a curve and a codimension two subvariety \Theta=C+Y. Then C is smooth, A is ... More
A Remark on Non-equivalent Star Products via Reduction for CP^nFeb 17 1998In this paper we construct non-equivalent star products on CP^n by phase space reduction. It turns out that the non-equivalent star products occur very natural in the context of phase space reduction by deforming the momentum map of the U(1)-action on ... More
The Covariant Picard Groupoid in Differential GeometrySep 23 2005In this article we discuss some general results on the covariant Picard groupoid in the context of differential geometry and interpret the problem of lifting Lie algebra actions to line bundles in the Picard groupoid approach.
Flavor physics with $Λ_b$ baryonsJan 13 2014Feb 26 2015At the LHC, bottom baryons are being produced in unprecedented quantities, which opens up a new field for flavor physics. For example, the decay $\Lambda_b \to p \mu^- \bar{\nu}$ can be used to obtain a novel determination of the CKM matrix element $|V_{ub}|$, ... More
A causal perspective on random geometryMay 02 2009In this thesis we investigate the importance of causality in non-perturbative approaches to quantum gravity. Firstly, causal sets are introduced as a simple kinematical model for causal geometry. It is shown how causal sets could account for the microscopic ... More
Hyperon-nucleon interaction and baryonic contact terms in SU(3) chiral effective field theoryDec 16 2013In this proceeding we summarize results for baryonic contact terms derived within SU(3) chiral effective field theory. The four-baryon contact terms, necessary for the description of the hyperon-nucleon interaction, include SU(3) symmetric and explicit ... More
Density of states near the Mott-Hubbard transition in the limit of large dimensionsMar 12 1998Oct 30 1998The zero temperature Mott-Hubbard transition as a function of the Coulomb repulsion U is investigated in the limit of large dimensions. The behavior of the density of states near the transition at U=U_c is analyzed in all orders of the skeleton expansion. ... More
A model of semimetallic behavior in strongly correlated electron systemsNov 17 1998Metals with values of the resistivity and the Hall coefficient much larger than typical ones, e.g., of sodium, are called semimetals. We suggest a model for semimetals which takes into account the strong Coulomb repulsion of the charge carriers, especially ... More
Phenomenological guide to physics beyond the Standard ModelFeb 14 2005Various aspects of physics beyond the Standard Model are discussed from the perspective of the fantastic phenomenological success of the Standard Model, its simplicity and predictive power
Status of the Minimal Supersymmetric Standard ModelOct 04 1995Recent results in study of the Minimal Supersymmetric Standard Model as the effective low energy theory give important hints for experimental search for supersymmetry. Also, in the bottom-up approach to explore weak scale - GUT scale connection, they ... More
The Kaon B-parameter in quenched QCDOct 02 2005I report on a recent determination by the ALPHA collaboration of the kaon B-parameter using lattice QCD with Wilson type quarks. An effort is made to control all systematic errors except for the quenched approximation. The preliminary result for the renormalization ... More
Non-perturbative Renormalization in Lattice Field TheoryNov 27 2000I review the strategies which have been developped in recent years to solve the non-perturbative renormalization problem in lattice field theories. Although the techniques are general, the focus will be on applications to lattice QCD. I discuss the momentum ... More
The Schrodinger functional with chirally rotated boundary conditionsNov 16 2005Using orbifold techniques I construct the Schrodinger functional (SF) for a doublet of Wilson quarks with chirally rotated boundary conditions. This allows to perform checks of universality: for instance, the renormalized SF coupling constant, defined ... More
Data Unfolding Methods in High Energy PhysicsNov 07 2016A selection of unfolding methods commonly used in High Energy Physics is compared. The methods discussed here are: bin-by-bin correction factors, matrix inversion, template fit, Tikhonov regularisation and two examples of iterative methods. Two procedures ... More
The semiclassical small-$\hbar$ limit of loci of roots of fundamental solutions for polynomial potentialsMay 04 2008Dec 15 2008In this paper a description of the small-$\hbar$ limit of loci of zeros of fundamental solutions for polynomial potentials is given. The considered cases of the potentials are bounded to the ones which provided us with simple turning points only. Among ... More
New opportunities with spectro-interferometry and spectro-astrometryDec 15 2013Latest-generation spectro-interferometric instruments combine a milliarcsecond angular resolution with spectral capabilities, resulting in an immensely increased information content. Here, I present methodological work and results that illustrate the ... More
A Common View on Strong, Uniform, and Other Notions of Equivalence in Answer-Set ProgrammingDec 06 2007Logic programming under the answer-set semantics nowadays deals with numerous different notions of program equivalence. This is due to the fact that equivalence for substitution (known as strong equivalence) and ordinary equivalence are different concepts. ... More
A generalized likelihood ratio test statistic for Cherenkov telescope dataDec 04 2011Jun 15 2012Astrophysical sources of TeV gamma rays are usually established by Cherenkov telescope observations. These counting type instruments have a field of view of few degrees in diameter and record large numbers of particle air showers via their Cherenkov radiation ... More
An amusing sequence of functionsOct 11 2016We consider the amusing sequence of functions $f_n: \mathbb{R} \rightarrow \mathbb{R}$ given by $$ f_n(x) = \sum_{k=1}^{n}{\frac{|\sin{(k \pi x)}|}{k}}.$$ Every rational point is eventually the location of a strict local minimum of $f_n$: more precisely, ... More
Generation of real algebraic loci via complex detoursOct 19 2015May 03 2016We discuss the locus generation algorithm used by the dynamic geometry software Cinderella, and how it uses complex detours to resolve singularities. We show that the algorithm is independent of the orientation of its complex detours. We conjecture that ... More
On the arithmetic rank of projective subspace arrangementsJul 08 2016If $V$ is a projective subspace arrangement over an infinite field, consisting of $m$ irreducible components all intersecting in the empty set, and each of codimension $c_i,i=1,\ldots,m$, then the arithmetic rank of the defining ideal of $V$ is bounded ... More
Power correction analyses in e+e- annihilationSep 29 2000The current status of theoretical work and experimental analyses on power corrections in QCD for e+e- annihilation will be reviewed. Measurements of the number of active quark flavours n_f and the QCD colour factors C_A and C_F derived from QCD fits to ... More
Deformations of WZW modelsDec 17 2003Jan 12 2004Current-current deformations for WZW models of semisimple compact groups are discussed in a sigma model approach. We start with the abelian rank one group U(1). Afterwards, we keep the rank one but allow for non abelian structures by considering SU(2). ... More
Gauging Flavour in Meta-Stable Susy Breaking ModelsAug 04 2006Aug 16 2006We modify the first ISS model (hep-th/0602239) by gauging a diagonal flavour symmetry. We add additional multiplets transforming as fundamentals and anti-fundamentals under the gauged flavour group. Their number is chosen such that the microscopic theory ... More
Strings, Branes and Extra DimensionsOct 05 2001Jan 03 2002This review is devoted to strings and branes. Firstly, perturbative string theory is introduced. The appearance of various types of branes is discussed. These include orbifold fixed planes, D-branes and orientifold planes. The connection to BPS vacua ... More
Polarization-anisotropy induced spatial anisotropy of polariton amplification in planar semiconductor microcavitiesNov 05 2007Based on a microscopic many-particle theory we investigate the amplification of polaritons in planar semiconductor microcavities. We study a spatially perfectly isotropic microcavity system and excitation geometry. For this system, our analysis shows ... More
Implementation and Evaluation of multimodal input/output channels for task-based industrial robot programmingMar 17 2015Programming industrial robots is not very intuitive, and the programmer has to be a domain expert for e.g. welding and programming to know how the task is optimally executed. For SMEs such employees are not affordable, nor cost-effective. Therefore a ... More
Lectures on configuration space methods for sunrise-type diagramsJul 23 2003In this lecture series I will give a fundamental insight into configuration space techniques which are of help to calculate a broad class of Feynman diagrams, the sunrise-type diagrams. Applications are shown along with basic concepts and techniques.
Analyzing QCD Sum Rules for Heavy Baryons at Next-to-Leading Order in α_SOct 15 1997In this talk I consider QCD sum rules for the ground state heavy baryons to leading order in $1/m_Q$ and at next-to-leading order in $\alpha_S$ within the context of Heavy Quark Symmetry. The analysis is done at a fixed scale $\mu=1 GeV$. The evolution ... More
On the Stokes matrices of the $tt^*$-Toda equationOct 01 2016We derive a formula for the signature of the symmetrized Stokes matrix $\cal{S}+\cal{S}^\mathrm{T}$ for the $tt^*$-Toda equation. As a corollary, we verify a conjecture of Cecotti and Vafa regarding when $\cal{S}+\cal{S}^\mathrm{T}$ is positive definite, ... More
Gaia - A White Dwarf Discovery MachineOct 30 2006The Gaia data will help to improve the construction of a luminosity function for the disk and the halo and will provide a more accurate determination of the age of our solar neighborhood. Moreover, reliable stellar dynamical investigations of the disk ... More
Gauge covariant heat kernel expansion at finite temperatureFeb 18 2003The heat kernel method is extended to the case of finite temperature. Special emphasis is given to the study of gauge theories. Due to the compactness of space in the Euclidean time direction (inverse temperature) the field strength cannot completely ... More
Resummation of soft modes in the free energy of Phi^4 theoryAug 26 1998Nov 24 1998A new method is proposed for the calculation of the free energy of an N-component Phi^4 theory at finite temperature. The method combines a perturbative treatment of the hard modes with a non-perturbative treatment in the effectively three-dimensional ... More
A model and sensitivity analysis of the quality economics of defect-detection techniquesDec 12 2016One of the main cost factors in software development is the detection and removal of defects. However, the relationships and influencing factors of the costs and revenues of defect-detection techniques are still not well understood. This paper proposes ... More