Results for "Jörg Neugebauer"

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Stationary two-black-hole configurations: A non-existence proofMay 29 2011Based on the solution of a boundary problem for disconnected (Killing) horizons and the resulting violation of characteristic black hole properties, we present a non-existence proof for equilibrium configurations consisting of two aligned rotating black ... More
Collisions of rigidly rotating disks of dust in General RelativityJun 07 2006Sep 25 2006We discuss inelastic collisions of two rotating disks by using the conservation laws for baryonic mass and angular momentum. In particular, we formulate conditions for the formation of a new disk after the collision and calculate the total energy loss ... More
Non-existence of stationary two-black-hole configurationsFeb 09 2010Jun 07 2010We resume former discussions of the question, whether the spin-spin repulsion and the gravitational attraction of two aligned sub-extremal black holes can balance each other. To answer the question we formulate a boundary value problem for two separate ... More
Non-existence of stationary two-black-hole configurations: The degenerate caseMar 27 2011In a preceding paper we examined the question whether the spin-spin repulsion and the gravitational attraction of two aligned sub-extremal black holes can balance each other. Based on the solution of a boundary value problem for two separate (Killing-) ... More
Anomalous phonon lifetime shortening in paramagnetic CrN caused by magneto-lattice coupling: A combined spin and ab initio molecular dynamics studyFeb 08 2018We study the mutual coupling of spin fluctuations and lattice vibrations in paramagnetic CrN by combining atomistic spin dynamics and ab initio molecular dynamics. The two degrees of freedom are dynamically coupled leading to non-adiabatic effects. Those ... More
Stationary black-hole binaries: A non-existence proofFeb 04 2013Jun 23 2014We resume former discussions of the question, whether the spin-spin repulsion and the gravitational attraction of two aligned black holes can balance each other. Based on the solution of a boundary problem for disconnected (Killing) horizons and the resulting ... More
Non-existence of stationary two-black-hole configurationsMay 26 2009Jun 25 2009We resume former discussions of the question, whether the spin-spin repulsion and the gravitational attraction of two aligned black holes can balance each other. To answer the question we formulate a boundary value problem for two separate (Killing-) ... More
Thermodynamic Description of Inelastic Collisions in General RelativityJan 24 2007Apr 03 2007We discuss head-on collisions of neutron stars and disks of dust ("galaxies") following the ideas of equilibrium thermodynamics, which compares equilibrium states and avoids the description of the dynamical transition processes between them. As an always ... More
Trends in the elastic response of binary early transition metal nitridesNov 11 2011Motivated by an increasing demand for coherent data that can be used for selecting materials with properties tailored for specific application requirements, we studied elastic response of nine binary early transition metal nitrides (ScN, TiN, VN, YN, ... More
Solutions of Einstein's field equations related to Jacobi's inversion problemFeb 14 2003A new class of exact solutions to the axisymmetric and stationary vacuum Einstein equations containing n arbitrary complex parameters and one arbitrary real solution of the axisymmetric three-dimensional Laplace equation is presented. The solutions are ... More
Ab initio study of pressure stabilised NiTi allotropes: pressure-induced transformations and hysteresis loopsOct 13 2011Dec 06 2011Changes in stoichiometric NiTi allotropes induced by hydrostatic pressure have been studied employing density functional theory. By modelling the pressure-induced transitions in a way that imitates quasi-static pressure changes, we show that the experimentally ... More
Ab initio study of point defects in NiTi-based alloysOct 15 2013Mar 20 2014Changes in temperature or stress state may induce reversible B2$\leftrightarrow$(R)$\leftrightarrow$ B19' martensitic transformations and associated shape memory effects in close-to-stoichiometric nickel-titanium (NiTi) alloys. Recent experimental studies ... More
Fully pseudospectral solution of the conformally invariant wave equation near the cylinder at spacelike infinity. II: Schwarzschild backgroundSep 22 2016It has recently been demonstrated (Class. Quantum Grav. 31, 085010, 2014) that the conformally invariant wave equation on a Minkowski background can be solved with a fully pseudospectral numerical method. In particular, it is possible to include spacelike ... More
Fully pseudospectral solution of the conformally invariant wave equation near the cylinder at spacelike infinityNov 26 2013Apr 02 2014We study the scalar, conformally invariant wave equation on a four-dimensional Minkowski background in spherical symmetry, using a fully pseudospectral numerical scheme. Thereby, our main interest is in a suitable treatment of spatial infinity, which ... More
Structural stability and thermodynamics of CrN magnetic phases from ab initio and experimentAug 14 2014The dynamical and thermodynamic phase stabilities of the stoichiometric compound CrN including different structural and magnetic configurations are comprehensively investigated using a first-principles density-functional-theory (DFT) plus U approach in ... More
Quantum-Confined Stark Effect in polar and nonpolar Wurtzite InN/GaN Heterostructures: Influence on Electronic Structure and Compensation by Coulomb AttractionJan 11 2013In this paper we systematically analyze the electronic structures of polar and nonpolar wurtzite-InN/GaN quantum dots and their modification due to the quantum-confined Stark effect caused by intrinsic fields. This is achieved by combining continuum elasticity ... More
A comparison of atomistic and continuum theoretical approaches to determine electronic properties of GaN/AlN quantum dotsNov 10 2008In this work we present a comparison of multiband k.p-models, the effective bond-orbital approach, and an empirical tight-binding model to calculate the electronic structure for the example of a truncated pyramidal GaN/AlN self-assembled quantum dot with ... More
Modeling of grain boundary dynamics using amplitude equationsJul 16 2014Aug 18 2014We discuss the modelling of grain boundary dynamics within an amplitude equations description, which is derived from classical density functional theory or the phase field crystal model. The relation between the conditions for periodicity of the system ... More
Macroscopic Elastic Properties of Textured ZrN--AlN Polycrystalline Aggregates: From Ab initio Calculations to Grain-Scale InteractionsOct 16 2013Jul 09 2014Despite the fast development of computational materials modelling, theoretical description of macroscopic elastic properties of textured polycrystalline aggregates starting from basic principles remains a challenging task. In this communication we use ... More
On computing the generalized Lambert seriesFeb 29 2012Jun 24 2012We show how the generalized Lambert series sum(n>=1, x*q^n/(1-x*q^n)) can be computed with Theta convergence. This allows the computation of the sum of the inverse Fibonacci numbers without splitting the sum into even and odd part. The method is a special ... More
Calculating initial data for the conformal Einstein equations by pseudo-spectral methodsJun 26 1998We present a numerical scheme for determining hyperboloidal initial data sets for the conformal field equations by using pseudo-spectral methods. This problem is split into two parts. The first step is the determination of a suitable conformal factor ... More
Natural domains for edge-degenerate differential operatorsJun 01 2010We study cone differential operators on the half-axis and edge-degenerate differential operators on a half-space. We construct subspaces of edge Sobolev spaces that can be considered as natural domains for edge-degenerate operators and indicate how they ... More
Strong martingale type and uniform smoothnessJul 28 2004We introduce stronger versions of the usual notions of martingale type p <= 2 and cotype q >= 2 of a Banach space X and show that these concepts are equivalent to uniform p-smoothness and q-convexity, respectively. All these are metric concepts, so they ... More
Pták's nondiscrete induction and its application to matrix iterationsMay 12 2014Vlastimil Pt\'ak's method of nondiscrete induction is based on the idea that in the analysis of iterative processes one should aim at rates of convergence as functions rather than just numbers, because functions may give convergence estimates that are ... More
Comparison of methods to extract an asymmetry parameter from dataApr 06 2011Sep 27 2011Several methods to extract an asymmetry parameter in an event distribution function are discussed and compared in terms of statistical precision and applicability. These methods are: simple counting rate asymmetries, event weighting procedures and the ... More
Robust multigrid for high-order discontinuous Galerkin methods: A fast Poisson solver suitable for high-aspect ratio Cartesian gridsMar 08 2016We present a polynomial multigrid method for nodal interior penalty and local discontinuous Galerkin formulations of the Poisson equation on Cartesian grids. For smoothing we propose two classes of overlapping Schwarz methods. The first class comprises ... More
Subset-lex: did we miss an order?May 26 2014Jan 09 2015We generalize a well-known algorithm for the generation of all subsets of a set in lexicographic order with respect to the sets as lists of elements (subset-lex order). We obtain algorithms for various combinatorial objects such as the subsets of a multiset, ... More
When is the (co)sine of a rational angle equal to a rational number?Jun 15 2010If the cosine of a rational multiple of $\pi$ is a rational number then it is an integral multiple of $\frac12$. For this fact, we give a proof accessible to an interested school student. We then discuss which quadratic and cubic irrationalities are values ... More
On the probability distribution function of the mass surface density of molecular clouds. IISep 19 2014The probability distribution function (PDF) of the mass surface density of molecular clouds provides essential information about the structure of molecular cloud gas and condensed structures out of which stars may form. In general, the PDF shows two basic ... More
Probing Color Response - Wakes in a Color PlasmaJun 30 2005The wake induced in a hot QCD medium by a high momentum parton (jet precursor) is calculated in the framework of linear response theory. Two different scenarios are discussed: a weakly coupled quark gluon plasma (pQGP) as described by hard-thermal loop ... More
Focus talk on interactions between jets and mediumSep 13 2005The energy and momentum lost by a hard parton propagating through hot and dense matter has to be redistributed during the nuclear medium evolution. Apart from heating the medium, there is the possibility that collective modes are excited leading to the ... More
Matched $G^k$-constructions yield $C^k$-continuous iso-geometric elementsJun 17 2014Sep 10 2014The note shows how $G^k$ (geometrically continuous surface) constructions yield $C^k$ iso-geometric elements also at irregular quad mesh points where three or more than four elements come together.
Improved Method to extract Nucleon Helicity Distributions using Event WeightingOct 21 2016An improved analysis method to extract quark helicity distributions from semi-inclusive double spin asymmetries in deep inelastic scattering is presented. The method relies on the fact that fragmentation functions, describing the fragmentation of a quark ... More
New Gowdy-symmetric vacuum and electrovacuum solutionsJan 13 2016Jun 02 2016We construct a 4-parameter family of inhomogeneous cosmological models, which contains two recently derived 3-parameter families as special cases. The corresponding exact vacuum solution to Einstein's field equations is obtained with methods from soliton ... More
Gowdy-Symmetric Vacuum and Electrovacuum SolutionsOct 06 2015"Smooth Gowdy-symmetric generalized Taub-NUT solutions" are a class of inhomogeneous cosmological vacuum models with a past and a future Cauchy horizon. In this proceedings contribution, we present families of exact solutions within that class, which ... More
Geometric relations for rotating and charged AdS black holesFeb 21 2014Jun 16 2014We derive mass-independent equations and inequalities for Kerr-Newman-anti-de Sitter black holes. In particular, we obtain an equation that relates electric charge, angular momentum and the areas of the event and Cauchy horizons. An area-angular momentum-charge ... More
Intermediate extension of Chow motives of Abelian typeNov 22 2012Sep 23 2016In this article, we give an unconditional construction of a motivic analogue of the intermediate extension in the context of Chow motives of Abelian type. Our main application concerns intermediate extensions of Chow motives associated to Kuga families ... More
The UMD constants of the summation operatorsJul 28 2004The UMD property of a Banach space is one of the most useful properties when one thinks about possible applications. This is in particular due to the boundedness of the vector-valued Hilbert transform for functions with values in such a space. Looking ... More
Refinability of splines derived from regular tessellationsOct 19 2012Dec 09 2012Splines can be constructed by convolving the indicator function of a cell whose shifts tessellate $\R^k$. This paper presents simple, non-algebraic criteria that imply that, for regular shift-invariant tessellations, only a small subset of such spline ... More
Computing SIAC spline coefficientsOct 01 2014The Discontinuous Galerkin (DG) method applied to hyperbolic differential equations outputs weakly-linked polynomial pieces. Post-processing these pieces by Smoothness-Increasing Accuracy-Conserving (SIAC) convolution with B-splines can improve the accuracy ... More
Some remarks on depth of dead ends in groupsMar 21 2007Mar 22 2007It is known, that the existence of dead ends (of arbitrary depth) in the Cayley graph of a group depends on the chosen set of generators. Nevertheless there exist many groups, which do not have dead ends of arbitrary depth with respect to any set of generators. ... More
Supercritical series expansion for the contact process in heterogeneous and disordered environmentsMay 14 2007The supercritical series expansion of the survival probability for the one-dimensional contact process in heterogeneous and disordered lattices is used for the evaluation of the loci of critical points and critical exponents $\beta$. The heterogeneity ... More
Truncated Variational Expectation MaximizationOct 10 2016We derive a novel variational expectation maximization approach based on truncated variational distributions. The truncated distributions are proportional to exact posteriors in a subset of a discrete state space and equal zero otherwise. In contrast ... More
Some Facets of Complexity Theory and Cryptography: A Five-Lectures TutorialNov 21 2001Dec 20 2002In this tutorial, selected topics of cryptology and of computational complexity theory are presented. We give a brief overview of the history and the foundations of classical cryptography, and then move on to modern public-key cryptography. Particular ... More
Exact Complexity of Exact-Four-ColorabilitySep 14 2001Let $M_k \seq \nats$ be a given set that consists of $k$ noncontiguous integers. Define $\exactcolor{M_k}$ to be the problem of determining whether $\chi(G)$, the chromatic number of a given graph $G$, equals one of the $k$ elements of the set $M_k$ exactly. ... More
The general classical solution of the superparticleJul 08 1994The theory of vectors and spinors in 9+1 dimensional spacetime is introduced in a completely octonionic formalism based on an octonionic representation of the Clifford algebra $\Cl(9,1)$. The general solution of the classical equations of motion of the ... More
k-Disjunctive cuts and a finite cutting plane algorithm for general mixed integer linear programsJul 26 2007In this paper we give a generalization of the well known split cuts of Cook, Kannan and Schrijver to cuts which are based on multi-term disjunctions. They will be called k-disjunctive cuts. The starting point is the question what kind of cuts is needed ... More
Measurement of Permanent Electric Dipole Moments of Charged Hadrons in Storage RingsJan 14 2013Jul 30 2013Permanent Electric Dipole Moments (EDMs) of elementary particles violate two fundamental symmetries: time reversal invariance (T) and parity (P). Assuming the CPT theorem this implies CP-violation. The CP-violation of the Standard Model is orders of magnitude ... More
The algebraic theory of Kreck surgeryApr 21 2004In the 1980s Matthias Kreck developed a modified surgery theory with obstructions in a hardly understood monoid $l_n(Z[\pi])$. This paper presents a couple of purely algebraic tools to find out whether an element in $l_{2q}(R)$ is "elementary" i.e. whether ... More
Weights and conservativitySep 11 2015Sep 21 2016The purpose of this article is to study conservativity in the context of triangulated categories equipped with a weight structure. As application, we establish (weight) conservativity for the restriction of the (generic) l-adic realization to the category ... More
Cooperative sequential adsorption with nearest-neighbor exclusion and next-nearest neighbor interactionJun 01 2008May 25 2009A model for cooperative sequential adsorption that incorporates nearest-neighbor exclusion and next-nearest neighbor interaction is presented. It is analyzed for the case of one-dimensional dimer and two-dimensional monomer adsorption. Analytic solutions ... More
Ellipticity in Pseudodifferential Algebras of Toeplitz TypeAug 19 2011Let L^\star be a filtered algebra of abstract pseudodifferential operators equipped with a notion of ellipticity, and T^\star be a subalgebra of operators of the form P_1AP_0, where P_0 and P_1 are two projections. The elements of L^\star act as linear ... More
On global regular solution branches and multiple solutions of the Boltzmann equationJan 06 2016Existence of global regular solution branches of the Boltzmann Cauchy problem with continuously differentiable data in phase space dimension $2d\geq 6$ with polynomial decay at infinity of order greater than $2d$ is proved. There are data in this class ... More
More cubic surfaces violating the Hasse principleJun 14 2010We generalize L.J. Mordell's construction of cubic surfaces for which the Hasse principle fails.
Motivic intersection complexApr 01 2011Apr 28 2011In this article, we give an unconditional definition of the motivic analogue of the intersection complex, establish its basic properties, and prove its existence in certain cases.
Fully pseudospectral time evolution and its application to 1+1 dimensional physical problemsApr 18 2012Dec 16 2012It was recently demonstrated that time-dependent PDE problems can numerically be solved with a fully pseudospectral scheme, i.e. using spectral expansions with respect to both spatial and time directions (Hennig and Ansorg, 2009 [15]). This was done with ... More
High Spatial Resolution HST/NICMOS Observations of Markarian 231Jul 19 2004Observations of Markarian 231 at 1.1 microns taken with NICMOS on the Hubble Space Telescope are described. The brightness of the object in the near infrared and the inherent short-term stability of the NICMOS optical and instrumental system enables application ... More
Electronic and structural properties of vacancies on and below the GaP(110) surfaceOct 28 1997May 19 1998We have performed total-energy density-functional calculations using first-principles pseudopotentials to determine the atomic and electronic structure of neutral surface and subsurface vacancies at the GaP(110) surface. The cation as well as the anion ... More
Studying null and time-like geodesics in the classroomApr 30 2011In a first course of general relativity it is usually quite difficult for students to grasp the concept of a geodesic. It is supposed to be straight (auto-parallel) and yet it 'looks' curved. In these situations it is very useful to have some explicit ... More
Algebraic stability analysis of constraint propagationOct 20 2004Aug 12 2005The divergence of the constraint quantities is a major problem in computational gravity today. Apparently, there are two sources for constraint violations. The use of boundary conditions which are not compatible with the constraint equations inadvertently ... More
Top-heavy IMFs in ultra compact dwarf galaxies?Jan 18 2012Ultra compact dwarf galaxies (UCDs) are dense stellar systems at the border between massive star-clusters and small galaxies. Their on average high optical mass-to-light (M/L) ratio cannot be explained by stellar populations with the canonical stellar ... More
Nonlinear evolution of electron shear flow instabilities in the presence of an external guide magnetic fieldAug 08 2016The dissipation mechanism by which the magnetic field reconnects in the presence of an external (guide) magnetic field in the direction of the main current is not well understood. In thin electron current sheets (ECS) (thickness ~ an electron inertial ... More
Effect of guide field on three dimensional electron shear flow instabilities in collisionless magnetic reconnectionNov 12 2014Apr 06 2015We examine the effect of an external guide field and current sheet thickness on the growth rates and nature of three dimensional unstable modes of an electron current sheet driven by electron shear flow. The growth rate of the fastest growing mode drops ... More
Random Diophantine inequalities of additive typeOct 16 2011Using the Davenport-Heilbronn circle method, we show that for almost all additive Diophantine inequalities of degree $k$ in more than $2k$ variables the expected asymptotic formula for the density of solutions holds true. This appears to be the first ... More
Stochastic Load-Redistribution Model for Cascading Failure PropagationSep 23 2009Jan 28 2010A new class of probabilistic models for cascading failure propagation in interconnected systems is proposed. The models take into account important characteristics of real systems that are not considered in existing generic approaches. Specifically, it ... More
Current Redistribution in Resistor Networks: Fat-Tail Statistics in Regular and Small-World NetworksOct 21 2016The redistribution of electrical currents in resistor networks after single-bond failures is analyzed in terms of current-redistribution factors that are shown to depend only on the topology of the network and on the values of the bond resistances. We ... More
False-Name Manipulation in Weighted Voting Games is Hard for Probabilistic Polynomial TimeMar 07 2013False-name manipulation refers to the question of whether a player in a weighted voting game can increase her power by splitting into several players and distributing her weight among these false identities. Analogously to this splitting problem, the ... More
Blow-up of the non-equivariant 2+1 dimensional wave mapMay 13 2012It has been known for a long time that the equivariant 2+1 wave map into the 2-sphere blows up if the initial data are chosen appropriately. Here, we present numerical evidence for the stability of the blow-up phenomenon under explicit violations of equivariance. ... More
Time-resolved analysis of strong-field induced plasmon oscillations in metal clusters by spectral interferometry with few-cycle laser fieldsNov 04 2010Feb 10 2011We propose a scheme for ultrafast real-time imaging of laser-induced collective electron oscillations (Mie plasmons) in gas phase metal clusters by interferometrically stable scanning of two intense few-cycle optical laser pulses. The feasibility of our ... More
On the number of certain Del Pezzo surfaces of degree four violating the Hasse principleJul 14 2015We give an asymptotic expansion for the density of del Pezzo surfaces of degree four in a certain Birch Swinnerton-Dyer family violating the Hasse principle due to a Brauer-Manin obstruction. Under the assumption of Schinzel's hypothesis and the finiteness ... More
The Hasse principle for lines on del Pezzo surfacesOct 21 2014Feb 25 2015In this paper, we consider the following problem: Does there exist a cubic surface over $\mathbb{Q}$ which contains no line over $\mathbb{Q}$, yet contains a line over every completion of $\mathbb{Q}$? This question may be interpreted as asking whether ... More
Absolute Continuity under Time Shift for Ornstein-Uhlenbeck type Processes with Delay or AnticipationNov 27 2014The paper is concerned with one-dimensional two-sided Ornstein-Uhlenbeck type processes with delay or anticipation. We prove existence and uniqueness requiring almost sure boundedness on the left half-axis in case of delay and almost sure boundedness ... More
General Upper Bounds on the Running Time of Parallel Evolutionary AlgorithmsJun 15 2012We present a new method for analyzing the running time of parallel evolutionary algorithms with spatially structured populations. Based on the fitness-level method, it yields upper bounds on the expected parallel running time. This allows to rigorously ... More
Violating the no-signaling principle with classical inseparable beams in an optical parity-time symmetric systemSep 05 2016We show that the no-signaling principle can be violated with classical inseparable beams in the presence of a parity-time (PT) symmetric subsystem. Thus, the problems associated to PT-symmetric quantum theories recently discovered by Lee et al. [Phys. ... More
Non-linear absorption and density dependent dephasing in Rydberg EIT-mediaMay 07 2013Oct 15 2013Light propagation through an ensemble of ultra-cold Rydberg atoms in electromagnetically induced transparency (EIT) configuration is studied. In strongly interacting Rydberg EIT media, non-linear optical effects lead to a non-trivial dependence of the ... More
Nonlinear Effects in Pulse Propagation through Doppler-Broadened Closed-Loop Atomic MediaNov 26 2007Nonlinear effects in pulse propagation through a medium consisting of four-level double-$\Lambda$-type systems are studied theoretically. We apply three continous-wave driving fields and a pulsed probe field such that they form a closed interaction loop. ... More
Stably diffeomorphic manifolds and l_{2q+1}(Z[π])Aug 14 2008Oct 23 2008The monoids l_{2q+1}(Z[\pi]) detect s-cobordisms amongst certain bordisms between stably diffeomorphic 2q-dimensional manifolds and generalise the Wall simple surgery obstruction groups, L_{2q+1}^s(Z[\pi]) \subset l_{2q+1}(Z[\pi]). In this paper we give ... More
The Tits alternative for non-spherical triangles of groupsMay 14 2014Jul 29 2014Triangles of groups have been introduced by Gersten and Stallings. They are, roughly speaking, a generalisation of the amalgamated free product of two groups and occur in the framework of Corson diagrams. First, we prove an intersection theorem for Corson ... More
Autonomous Cleaning of Corrupted Scanned Documents - A Generative Modeling ApproachJan 12 2012Jul 02 2012We study the task of cleaning scanned text documents that are strongly corrupted by dirt such as manual line strokes, spilled ink etc. We aim at autonomously removing dirt from a single letter-size page based only on the information the page contains. ... More
Mosco Type Convergence of Bilinear Forms and Weak Convergence of $n$-Particle SystemsSep 21 2012Feb 09 2015It is well known that Mosco (type) convergence is a tool in order to verify weak convergence of finite dimensional distributions of sequences of stochastic processes. In the present paper we are concerned with the concept of Mosco type convergence for ... More
Number systems over ordersAug 16 2017Let $\mathbb{K}$ be a number field of degree $k$ and let $\mathcal{O}$ be an order in $\mathbb{K}$. A generalized number system over $\mathcal{O}$ (GNS for short) is a pair $(p,\mathcal{D})$ where $p \in \mathcal{O}[x]$ is monic and $\mathcal{D}\subset\mathcal{O}$ ... More
$\boldsymbolβ$-adic Halton sequencesOct 17 2016Van der Corput and Halton sequences are well-known low-discrepancy sequences. Almost twenty years ago Ninomiya defined analogues of van der Corput sequences for $\beta$-numeration and proved that they also form low-discrepancy sequences if $\beta$ is ... More
Bounding, splitting, and almost disjointnessNov 21 2012We investigate some aspects of bounding, splitting, and almost disjointness. In particular, we investigate the relationship between the bounding number, the closed almost disjointness number, splitting number, and the existence of certain kinds of splitting ... More
Fractal-driven distortion of resting state functional networks in fMRI: a simulation studyAug 04 2012Fractals are self-similar and scale-invariant patterns found ubiquitously in nature. A lot of evidences implying fractal properties such as 1/f power spectrums have been also observed in resting state fMRI time series. To explain the fractal behavior ... More
Maximal $L_p$-regularity of non-local boundary value problemsJul 09 2014We investigate the $\mathcal R$-boundedness of operator families belonging to the Boutet de Monvel calculus. In particular, we show that weakly and strongly parameter-dependent Green operators of nonpositive order are $\mathcal R$-bounded. Such operators ... More
Coloring ordinals by realsApr 14 2007We study combinatorial principles we call Homogeneity Principle HP(\kappa) and Injectivity Principle IP(\kappa,\lambda) for regular \kappa>\aleph_1 and \lambda\leq\kappa which are formulated in terms of coloring the ordinals <\kappa by reals.
Complexity of the Exact Domatic Number Problem and of the Exact Conveyor Flow Shop ProblemDec 09 2002Mar 23 2004We prove that the exact versions of the domatic number problem are complete for the levels of the boolean hierarchy over NP. The domatic number problem, which arises in the area of computer networks, is the problem of partitioning a given graph into a ... More
Is the existence of a softest point in the directed flow excitation function an unambiguous signal for the creation of a quark-gluon plasma?May 27 2002The excitation function of the in-plane directed flow of nucleons is studied within a non-equilibrium transport approach. It is demonstrated that a local minimum in the excitation function of the directed flow develops, which is not related to a transition ... More
Sequential Tunneling through Molecular Spin RingsAug 29 2006Mar 19 2007We consider electrical transport through molecules with Heisenberg-coupled spins arranged in a ring structure in the presence of an easy-axis anisotropy. The molecules are coupled to two metallic leads and a gate. In the charged state of the ring, a Zener ... More
Cotunneling current through quantum dots with phonon-assisted spin-flip processesSep 15 2005Jan 30 2006We consider cotunneling through a quantum dot in the presence of spin-flip processes induced by the coupling to acoustic phonons of the surrounding. An expression for the phonon-assisted cotunneling current is derived by means of a generalized Schrieffer-Wolff ... More
Numerical evolution of plane gravitational waves in the Friedrich-Nagy gaugeMar 06 2014Jul 25 2014The first proof of well-posedness of an initial boundary value problem for the Einstein equations was given in 1999 by Friedrich and Nagy. They used a frame formalism with a particular gauge for formulating the equations. This `Friedrich-Nagy' (FN) gauge ... More
Random diophantine equations, IDec 19 2012We consider additive diophantine equations of degree $k$ in $s$ variables and establish that whenever $s\ge 3k+2$ then almost all such equations satisfy the Hasse principle. The equations that are soluble form a set of positive density, and among the ... More
Transfer Function Synthesis without Quantifier EliminationJul 18 2012Sep 28 2012Traditionally, transfer functions have been designed manually for each operation in a program, instruction by instruction. In such a setting, a transfer function describes the semantics of a single instruction, detailing how a given abstract input state ... More
Classical Polylogarithm -- Abstract of a series of lectures given at the workshop on polylogs in Essen, May 1 -- 4, 1997Oct 08 2012These are extended abstracts from an series of lectures in 1997. The text has not been updated since then. We explain the construction of the motivic polylog as published in Annette Huber, J\"org Wildeshaus, Classical Motivic Polylogarithm According to ... More
Counting in hyperbolic spikes: the diophantine analysis of multihomogeneous diagonal equationsFeb 05 2014A method is described to sum multi-dimensional arithmetic functions subject to hyperbolic summation conditions, provided that asymptotic formulae in rectangular boxes are available. In combination with the circle method, the new method is a versatile ... More
Cowen-Douglas tuples and fiber dimensionsJan 11 2016Let T be a Cowen-Douglas tuple on a Banach space X. We use functional representations of T to associate with each T-invariant subspace Y of X an integer called the fiber dimension of Y. Among other results we prove a limit formula for the fiber dimension, ... More
The field of values bound on ideal GMRESNov 26 2012Apr 09 2013A widely known result of Howard Elman, and its improvements due to Gerhard Starke, Michael Eiermann and Oliver Ernst, gives a bound on the (worst-case) GMRES residual norm using quantities related to the field of values of the given matrix and of its ... More
Nonparametric Analysis of Random Utility ModelsJun 15 2016This paper develops and implements a nonparametric test of Random Utility Models. The motivating application is to test the null hypothesis that a sample of cross-sectional demand distributions was generated by a population of rational consumers. We test ... More
On the Brauer-Manin obstruction for degree four del Pezzo surfacesMar 28 2015We show that, for every integer $1 \leq d \leq 4$ and every finite set $S$ of places, there exists a degree $d$ del Pezzo surface $X$ over ${\mathbb Q}$ such that ${\rm Br}(X)/{\rm Br}({\mathbb Q}) \cong {\mathbb Z}/2{\mathbb Z}$ and the Brauer-Manin ... More
The interior of axisymmetric and stationary black holes: Numerical and analytical studiesMar 23 2011We investigate the interior hyperbolic region of axisymmetric and stationary black holes surrounded by a matter distribution. First, we treat the corresponding initial value problem of the hyperbolic Einstein equations numerically in terms of a single-domain ... More