Results for "C. Richter"

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Motion Scaling Solutions for Improved Performance in High Delay Surgical TeleoperationFeb 08 2019Robotic teleoperation brings great potential for advances within the field of surgery. The ability of a surgeon to reach patient remotely opens exciting opportunities. Early experience with telerobotic surgery has been interesting, but the clinical feasibility ... More
Commutative ring spectraOct 06 2017In this survey paper on commutative ring spectra we present some basic features of commutative ring spectra and discuss model category structures. As a first interesting class of examples of such ring spectra we focus on (commutative) algebra spectra ... More
Dynamic landscape models of coevolutionary gamesNov 28 2016Mar 15 2017Players of coevolutionary games may update not only their strategies but also their networks of interaction. Based on interpreting the payoff of players as fitness, dynamic landscape models are proposed. The modeling procedure is carried out for Prisoner's ... More
Properties of interaction networks, structure coefficients, and benefit-to-cost ratiosMay 29 2018Jun 06 2018In structured populations the spatial arrangement of cooperators and defectors on the interaction graph together with the structure of the graph itself determines the game dynamics and particularly whether or not fixation of cooperation (or defection) ... More
Analyzing coevolutionary games with dynamic fitness landscapesMar 21 2016Coevolutionary games cast players that may change their strategies as well as their networks of interaction. In this paper a framework is introduced for describing coevolutionary game dynamics by landscape models. It is shown that coevolutionary games ... More
Fixation properties of multiple cooperator configurations on regular graphsNov 16 2018Mar 20 2019Whether or not cooperation is favored in evolutionary games on graphs depends on the population structure and spatial properties of the interaction network. Population structures can be expressed as configurations. Such configurations extend scenarios ... More
A lower bound for coherences on the Brown-Peterson spectrumApr 15 2005Feb 27 2009We provide a lower bound for the coherence of the homotopy commutativity of the Brown-Peterson spectrum, BP, at a given prime p and prove that it is at least (2p^2 + 2p - 2)-homotopy commutative. We give a proof based on Dyer-Lashof operations that BP ... More
Codynamic Fitness Landscapes of Coevolutionary Minimal SubstratesApr 23 2014Coevolutionary minimal substrates are simple and abstract models that allow studying the relationships and codynamics between objective and subjective fitness. Using these models an approach is presented for defining and analyzing fitness landscapes of ... More
Relationships between dilemma strength and fixation properties in coevolutionary gamesJan 11 2019May 13 2019Whether or not cooperation is favored over defection in evolutionary games can be assigned by structure coefficients for any arrangement of cooperators and defectors on any network modeled as a regular graph. We study how these structure coefficients ... More
Exact Relativistic Gravitational Field of a Stationary Counterrotating Dust DiskAug 13 1999Disks of collisionless particles are important models for certain galaxies and accretion disks in astrophysics. We present here a solution to the stationary axisymmetric Einstein equations which represents an infinitesimally thin dust disk consisting ... More
Physically Realistic Solutions to the Ernst Equation on Hyperelliptic Riemann SurfacesJun 10 1998Oct 07 1998We show that the class of hyperelliptic solutions to the Ernst equation (the stationary axisymmetric Einstein equations in vacuum) previously discovered by Korotkin and Neugebauer and Meinel can be derived via Riemann-Hilbert techniques. The present paper ... More
Quantum speedup of classical mixing processesSep 26 2006Apr 05 2007Most approximation algorithms for #P-complete problems (e.g., evaluating the permanent of a matrix or the volume of a polytope) work by reduction to the problem of approximate sampling from a distribution $\pi$ over a large set $\S$. This problem is solved ... More
Two remarks on the local Hamiltonian problemDec 27 2007In this note we present two natural restrictions of the local Hamiltonian problem which are BQP-complete under Karp reduction. Restrictions complete for QCMA, QMA_1, and MA were demonstrated previously.
Penning ionization of acene molecules by He nanodropletsJan 11 2018Acene molecules (anthracene, tetracene, pentacene) and fullerene (C$_{60}$) are embedded in He nanodroplets (He$_N$) and probed by EUV synchrotron radiation. When resonantly exciting the He nanodroplets, the embedded molecules M are efficiently ionized ... More
The nature of NV absorbers at high redshiftJul 29 2008Jan 23 2009We present a study of NV absorption systems at 1.5 < z < 2.5 in the optical spectra of 19 QSOs. Our analysis includes both absorbers arising from the intergalactic medium as well as systems in the vicinity of the background quasar. We construct detailed ... More
Assessing robustness of radiomic features by image perturbationJun 18 2018Image features need to be robust against differences in positioning, acquisition and segmentation to ensure reproducibility. Radiomic models that only include robust features can be used to analyse new images, whereas models with non-robust features may ... More
Riemann-Hilbert Problems for the Ernst Equation and Fibre BundlesNov 12 1998Riemann--Hilbert techniques are used in the theory of completely integrable differential equations to generate solutions that contain a free function which can be used at least in principle to solve initial or boundary value problems. The solution of ... More
Almost uniform sampling via quantum walksJun 24 2006Sep 18 2006Many classical randomized algorithms (e.g., approximation algorithms for #P-complete problems) utilize the following random walk algorithm for {\em almost uniform sampling} from a state space $S$ of cardinality $N$: run a symmetric ergodic Markov chain ... More
Dust depletion of Ca and Ti in QSO absorption line systemsMay 10 2016To explore the role of titanium- and calcium-dust depletion in gas in and around galaxies we systematically study Ti/Ca abundance ratios in intervening absorption-line systems at low and high redshift. We investigate high-resolution optical spectra obtained ... More
Towards topological Hochschild homology of Johnson-Wilson spectraJul 06 2018Oct 04 2018We offer a complete description of $THH(E(2))$ under the assumption that the Johnson-Wilson spectrum $E(2)$ at a chosen odd prime carries an $E_\infty$-structure. We also place $THH(E(2))$ in a cofiber sequence $E(2) \rightarrow THH(E(2))\rightarrow \overline{THH}(E(2))$ ... More
Towards a semiclassical understanding of chaotic single- and many-particle quantum dynamics at post-Heisenberg time scalesMar 22 2019Despite considerable progress during the last decades in devising a semiclassical theory for classically chaotic quantum systems a quantitative semiclassical understanding of their dynamics at late times (beyond the so-called Heisenberg time $T_H$) is ... More
Adaptation for nonparametric estimators of locally stationary processesFeb 27 2019Two adaptive bandwidth selection methods for nonparametric estimators in locally stationary processes are proposed. We investigate a cross validation approach and a method based on contrast minimization and derive asymptotic properties of both methods. ... More
Set-up for multi coincidence experiments of EUV to VIS photons and charged particles -- the solid angle maximization approachJun 11 2019The coincident detection of particles is a powerful method in experimental physics, enabling the investigation of a variety of projectile-target interactions. The vast majority of coincidence experiments is performed with charged particles, as they can ... More
A spectral sequence for the homology of a finite algebraic deloopingFeb 04 2013Oct 29 2015In the world of chain complexes E_n-algebras are the analogues of based n-fold loop spaces in the category of topological spaces. Fresse showed that operadic E_n-homology of an E_n-algebra computes the homology of an n-fold algebraic delooping. The aim ... More
Quasisymmetric functions from a topological point of viewMay 30 2006Oct 26 2007It is well-known that the homology of the classifying space of the unitary group is isomorphic to the ring of symmetric functions, Symm. We offer the cohomology of the loop space of the suspension of the infinite complex projective space as a topological ... More
An algebraic model for commutative HZ-algebrasNov 26 2014Jan 12 2017We show that the homotopy category of commutative algebra spectra over the Eilenberg-Mac Lane spectrum of the integers is equivalent to the homotopy category of E-infinity-monoids in unbounded chain complexes. We do this by establishing a chain of Quillen ... More
Some properties of Lubin-Tate cohomology for classifying spaces of finite groupsMay 10 2010May 31 2011We consider brave new cochain extensions $F(BG_+,R)\to F(EG_+,R)$, where $R$ is either a Lubin-Tate spectrum $E_n$ or the related 2-periodic Morava K-theory $K_n$, and $G$ is a finite group. When $R$ is an Eilenberg-Mac Lane spectrum, in some good cases ... More
Realizability of algebraic Galois extensions by strictly commutative ring spectraJun 16 2004Nov 18 2005We discuss some of the basic ideas of Galois theory for commutative S-algebras originally formulated by John Rognes. We restrict attention to the case of finite Galois groups and to global Galois extensions. We describe parts of the general framework ... More
A strictly commutative model for the cochain algebra of a spaceJan 03 2018Sep 24 2018The commutative differential graded algebra $A_{\mathrm{PL}}(X)$ of polynomial forms on a simplicial set $X$ is a crucial tool in rational homotopy theory. In this note, we construct an integral version $A^{\mathcal{I}}(X)$ of $A_{\mathrm{PL}}(X)$. Our ... More
Galois extensions of Lubin-Tate spectraOct 26 2007Sep 02 2008Let E_n be the n-th Lubin-Tate spectrum at a prime p. There is a commutative S-algebra E^{nr}_n whose coefficients are built from the coefficients of E_n and contain all roots of unity whose order is not divisible by p. For odd primes p we show that E^{nr}_n ... More
Discrete Time Term Structure Theory and Consistent Recalibration ModelsSep 05 2014We develop theory and applications of forward characteristic processes in discrete time following a seminal paper of Jan Kallsen and Paul Kr\"uhner. Particular emphasis is placed on the dynamics of volatility surfaces which can be easily formulated and ... More
Transport and two-way coupling effect of inertial particles by large-scale and very-large-scale motions in turbulenceJun 05 2019Direct numerical simulations two-way coupled with inertial particles are used to investigate the particle distribution and two-way coupling effect of low-inertia ($St_{LSM}=0.0625$, $St_{VLSM}=0.009$) and high-inertia ($St_{LSM}=0.475$, $St_{VLSM}=0.069$) ... More
Uniqueness of $E_\infty$ structures for connective coversJun 21 2005May 26 2006We refine our earlier work on the existence and uniqueness of E-infinity structures on K-theoretic spectra to show that at each prime p, the connective Adams summand has an essentially unique structure as a commutative S-algebra. For the p-completion ... More
$Γ$-cohomology of rings of numerical polynomials and $E_\infty$ structures on K-theoryApr 29 2003Apr 25 2005We investigate Gamma-cohomology of some commutative cooperation algebras E_*E associated with certain periodic cohomology theories. For KU and E(1), the Adams summand at a prime p, and for KO we show that Gamma-cohomology vanishes above degree 1. As these ... More
Some properties of the Thom spectrum over loop suspension of complex projective spaceJul 20 2012Jan 16 2013This note provides a reference for some properties of the Thom spectrum $M\xi$ over $\Omega\Sigma\CPi$. Some of this material is used in recent work of Kitchloo and Morava. We determine the $M\xi$-cohomology of $\CPi$ and show that $M\xi^*(\CPi)$ injects ... More
On the Grassmannian homology of $\mathbbm{F}_2$ and $\mathbbm{F}_3$Feb 14 2010Jul 02 2010We prove the vanishing of the subgroup of Bloch's cubical higher Chow groups $CH^2(\text{Spec}(\MF_p),3)$, $p=2,3$, generated by the images of corresponding projective Grassmannian homology groups ${}^PGH_1^2(\MF_p)$ using computer calculations.
The magnetic susceptibility of disordered non-diffusive mesoscopic systemsMar 17 1999Disorder-induced spectral correlations of mesoscopic quantum systems in the non-diffusive regime and their effect on the magnetic susceptibility are studied. We perform impurity averaging for non-translational invariant systems by combining a diagrammatic ... More
From clean to diffusive mesoscopic systems: A semiclassical approach to the magnetic susceptibilityJun 18 1998We study disorder-induced spectral correlations and their effect on the magnetic susceptibility of mesoscopic quantum systems in the non-diffusive regime. By combining a diagrammatic perturbative approach with semiclassical techniques we perform impurity ... More
The structure of Siegel modular forms modulo p and U(p) congruencesDec 19 2013We determine the ring structure of Siegel modular forms of degree g modulo a prime p, extending Nagaoka's result in the case of degree g=2. We characterize U(p) congruences of Jacobi forms and Siegel modular forms, and surprisingly find different behaviors ... More
Skewness-kurtosis adjusted confidence estimators and significance testsApr 10 2015First and second kind modifications of usual confidence intervals for estimating the expectation and of usual local alternative parameter choices are introduced in a way such that the asymptotic behavior of the true non-covering probabilities and the ... More
Effects of in-chain and off-chain substitutions on spin fluctuations in the spin-Peierls compound CuGeO_3Mar 06 1997The effect of in-chain and off-chain substitutions on 1D spin fluctuations in the spin-Peierls compound CuGeO_3 has been studied using Raman scattering in order to understand the interplay between defect induced states, enhanced spin-spin correlations ... More
Field-Effect Devices Utilizing LaAlO$_3$-SrTiO$_3$ InterfacesJan 28 2012Using LaAlO$_3$-SrTiO$_3$ bilayers, we have fabricated field-effect devices that utilize the two-dimensional electron liquid generated at the bilayers' {\textit n}-type interfaces as drain-source channels and the LaAlO$_3$ layers as gate dielectrics. ... More
Highly anisotropic magnetic states of Co dimers bound to graphene-vacanciesMay 15 2012The adsorption behavior and the magnetic states of cobalt atoms and dimers on single vacancies in a graphene sheet are investigated by means of relativistic density functional calculations. It is found that local magnetic moments are formed in both cases, ... More
A spectral refinement of the Bergelson-Host-Kra decomposition and new multiple ergodic theoremsSep 12 2016Jun 20 2017We investigate how spectral properties of a measure preserving system $(X,\mathcal{B},\mu,T)$ are reflected in the multiple ergodic averages arising from that system. For certain sequences $a:\mathbb{N}\to\mathbb{N}$ we provide natural conditions on the ... More
Large subsets of discrete hypersurfaces in $\mathbb{Z}^d$ contain arbitrarily many collinear pointsJan 29 2015Feb 04 2016In 1977 L.T. Ramsey showed that any sequence in $\mathbb{Z}^2$ with bounded gaps contains arbitrarily many collinear points. Thereafter, in 1980, C. Pomerance provided a density version of this result, relaxing the condition on the sequence from having ... More
Bringing Together Dynamic Geometry Software and the Graphics Processing UnitAug 14 2018We equip dynamic geometry software (DGS) with a user-friendly method that enables massively parallel calculations on the graphics processing unit (GPU). This interplay of DGS and GPU opens up various applications in education and mathematical research. ... More
The role of Zhang-Rice singlet-like excitations in one-dimensional cupratesJan 27 2000We present the first calculation of the electron-energy loss spectrum of infinite one-dimensional undoped CuO_3 chains within a multi-band Hubbard model. The results show good agreement with experimental spectra of Sr_2CuO_3. The main feature in the spectra ... More
The transition from an ordered antiferromagnet to a quantum disordered spin liquid in a solvable bilayer modelOct 26 1995We present a spin-1/2 bilayer model for the quantum order-disorder transition which (i) can be solved by mean-field theory for bulk quantities, (ii) becomes critical at the transition, and (iii) allows to include intralayer frustration. We present numerical ... More
High-resolution observations of two OVI absorbers at z=2 towards PKS 1448-232Oct 20 2011To explore the ionization conditions in highly-ionized absorbers at high redshift we have studied in detail two intervening OVI absorbers at z=2 towards the quasar PKS1448-232, based on high (R=75,000) and intermediate (R=45,000) resolution optical VLT/UVES ... More
Cu-O network dependent core-hole screening in low-dimensional cuprates: A theoretical analysisMar 11 2000We analyze the influence of the dimensionality on the Cu 2p_3/2 core level X-ray photoemission spectra of undoped cuprates. Both exchange splitting and delocalization properties are described within one framework using a multi-band Hubbard model. The ... More
Emission from Water Vapor and Absorption from Other Gases at 5-7.5 Microns in Spitzer-IRS Spectra of Protoplanetary DisksJul 09 2014We present spectra of 13 T Tauri stars in the Taurus-Auriga star-forming region showing emission in Spitzer Space Telescope Infrared Spectrograph (IRS) 5-7.5 micron spectra from water vapor and absorption from other gases in these stars' protoplanetary ... More
Embedding convex geometries and a bound on convex dimensionFeb 06 2015Oct 13 2016The notion of an abstract convex geometry offers an abstraction of the standard notion of convexity in a linear space. Kashiwabara, Nakamura and Okamoto introduce the notion of a generalized convex shelling into $\mathbb{R}$ and prove that a convex geometry ... More
Chemical Gating of a Weak Topological Insulator: Bi14Rh3I9Oct 10 2017The compound Bi14Rh3I9 has recently been suggested as a weak three-dimensional topological insulator on the basis of angle-resolved photoemission and scanning-tunneling experiments in combination with density functional (DF) electronic structure calculations. ... More
Poincare duality and Periodicity, II. James PeriodicityDec 29 2008Let K be a connected finite complex. This paper studies the problem of whether one can attach a cell to some iterated suspension S^j K so that the resulting space satisfies Poincare duality. When this is possible, we say that S^j K is a spine. We introduce ... More
Poincare duality and PeriodicityJul 10 2007Oct 16 2009We construct periodic families of Poincare complexes, partially solving a question of Hodgson that was posed in the proceedings of the 1982 Northwestern homotopy theory conference. We also construct infinite families of Poincare complexes whose top cell ... More
Phase separation in star polymer-colloid mixturesOct 12 2000We examine the demixing transition in star polymer-colloid mixtures for star arm numbers f=2,6,16,32 and different star-colloid size ratios. Theoretically, we solve the thermodynamically self-consistent Rogers-Young integral equations for binary mixtures ... More
Experimental Test of a Trace Formula for a Chaotic Three Dimensional Microwave CavityJun 18 2002Jul 22 2002We have measured resonance spectra in a superconducting microwave cavity with the shape of a three-dimensional generalized Bunimovich stadium billiard and analyzed their spectral fluctuation properties. The experimental length spectrum exhibits contributions ... More
Coexistence of Magnetic Order and Two-dimensional Superconductivity at LaAlO$_3$/SrTiO$_3$ InterfacesMay 02 2011A two dimensional electronic system with novel electronic properties forms at the interface between the insulators LaAlO$_3$ and SrTiO$_3$. Samples fabricated until now have been found to be either magnetic or superconducting, depending on growth conditions. ... More
Spin filtering and magnetoresistance in ballistic tunnel junctionsMar 21 2001Oct 19 2001We theoretically investigate magnetoresistance (MR) effects in connection with spin filtering in quantum-coherent transport through tunnel junctions based on non-magnetic/semimagnetic heterostructures. We find that spin filtering in conjunction with the ... More
Holomorphic projections and Ramanujan's mock theta functionsJun 17 2013Feb 10 2014We employ spectral methods of automorphic forms to establish a holomorphic projection operator for tensor products of vector-valued harmonic weak Maass forms and vector-valued modular forms. We apply this operator to discover simple recursions for Fourier ... More
The sub-DLA toward HE0001-2340: galaxy formation at z=2May 17 2005We present a detailed analysis of chemical abundances in a sub-damped Ly alpha absorber (sub-DLA) at z=2.187 towards the quasar HE0001-2340 (z_em=2.28) using VLT/UVES data. This sub-DLA system consists of at least 25 individual subcomponents spanning ... More
On the hitting times of quantum versus random walksAug 01 2008In this paper we define new Monte Carlo type classical and quantum hitting times, and we prove several relationships among these and the already existing Las Vegas type definitions. In particular, we show that for some marked state the two types of hitting ... More
R-matrix theory of driven electromagnetic cavitiesMar 18 2003Jul 17 2003Resonances of cylindrical symmetric microwave cavities are analyzed in R-matrix theory which transforms the input channel conditions to the output channels. Single and interfering double resonances are studied and compared with experimental results, obtained ... More
Magnetic susceptibility of frustrated spin-s J1-J2 quantum Heisenberg magnets: High-temperature expansion and exact diagonalization dataJan 22 2014Motivated by recent experiments on low-dimensional frustrated quantum magnets with competing nearest-neighbor exchange coupling J1 and next nearest-neighbor exchange coupling J2 we investigate the magnetic susceptibility of two-dimensional J1-J2 Heisenberg ... More
Analytical ground state for the three-band Hubbard modelApr 17 1999For the calculation of charge excitations as those observed in, e.g., photo-emission spectroscopy or in electron-energy loss spectroscopy, a correct description of ground-state charge properties is essential. In strongly correlated systems like the undoped ... More
Open-Sourced Reinforcement Learning Environments for Surgical RoboticsMar 05 2019Reinforcement Learning (RL) is a machine learning framework for artificially intelligent systems to solve a variety of complex problems. Recent years has seen a surge of successes solving challenging games and smaller domain problems, including simple ... More
Simplicity of Ore monoid ringsMay 08 2017Apr 12 2019Given a non-associative unital ring $R$, a monoid $G$ and a set $\pi$ of additive maps $R \rightarrow R$, we introduce the Ore monoid ring $R[\pi ; G]$, and, in a special case, the differential monoid ring. We show that these structures generalize, in ... More
Extending Drawings of Graphs to Arrangements of PseudolinesApr 25 2018A pseudoline is a homeomorphic image of the real line in the plane so that its complement is disconnected. An arrangement of pseudolines is a set of pseudolines in which every two cross exactly once. A drawing of a graph is pseudolinear if the edges can ... More
The influence of atomic alignment on absorption and emission spectroscopyJul 09 2018Spectroscopic observations play essential roles in astrophysics. They are crucial for determining physical parameters in the universe, providing information about the chemistry of various astronomical environments. The proper execution of the spectroscopic ... More
Brauer groups for commutative $S$-algebrasMay 28 2010Feb 02 2012We investigate a notion of Azumaya algebras in the context of structured ring spectra and give a definition of Brauer groups. We investigate their Galois theoretic properties, and discuss examples of Azumaya algebras arising from Galois descent and cyclic ... More
Automatic Generation of Bounds for Polynomial Systems with Application to the Lorenz SystemDec 21 2017Jun 06 2018This study covers an analytical approach to calculate positively invariant sets of dynamical systems. Using Lyapunov techniques and quantifier elimination methods, an automatic procedure for determining bounds in the state space as an enclosure of attractors ... More
On the crossing number of K_13Jul 12 2013Since the crossing number of K_{12} is now known to be 150, it is well-known that simple counting arguments and Kleitman's parity theorem for the crossing number of K_{2n+1} combine with a specific drawing of K_{13} to show that the crossing number of ... More
Microdeflectometry - a novel tool to acquire 3D microtopography with nanometer height resolutionOct 24 2007Feb 15 2008We introduce "microdeflectometry", a novel technique for measuring the microtopography of specular surfaces. The primary data is the local slope of the surface under test. Measuring the slope instead of the height implies high information efficiency and ... More
Impulsive laser-induced alignment of OCS molecules at FERMIAug 22 2018Aug 24 2018We demonstrate the experimental realization of impulsive alignment of carbonyl sulfide (OCS) molecules at the Low Density Matter Beamline (LDM) at the free-electron laser FERMI. OCS molecules in a molecular beam were impulsively aligned using 200 fs pulses ... More
The Variability and Period Analysis for the BL Lac AO 0235+164Feb 19 2017Variability is one of the extreme observational properties of BL Lacertae objects. AO 0235+164 is a well studied BL Lac through the whole electro-magnetic wavebands. In the present work, we show its optical R band photometric observations carried out ... More
High quality cobalt ferrite ultrathin films with large inversion parameter grown in epitaxy on Ag(001)Jun 29 2018Cobalt ferrite ultrathin films with inverse spinel structure are among the best candidates for spin-filtering at room temperature. We have fabricated high-quality epitaxial ultrathin CoFe2O4 layers on Ag(001) following a three-step method: an ultrathin ... More
H_2 absorption in a dense interstellar filament in the Milky Way haloMay 01 2003We investigate interstellar absorption from molecular hydrogen (H_2) and metals in an intermediate-velocity cloud (IVC) in the direction of the LMC star Sk -68 80 (HD 36521), based on data from the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. ... More
The most metal-poor damped Ly alpha system at z<3: constraints on early nucleosynthesisFeb 06 2006To constrain the conditions for very early nucleosynthesis in the Universe we compare the chemical enrichment pattern of an extremely metal-poor damped Lyman alpha (DLA) absorber with predictions from recent explosive nucleosynthesis model calculations. ... More
Optimal drawings of $K_{p,q}$ in surfaces, $p$ fixed, $q$ largeJun 11 2018For a fixed positive integer $p$ and surface $\Sigma$, there is a finite set $\mathcal{D}(p,\Sigma)$ of `good' drawings of complete bipartite graphs $K_{p,r}$ (with possible varying $r$) such that, for every good drawing $D$ of $K_{p,q}$, there is a good ... More
Graphs with at most one crossingJan 28 2019Apr 26 2019The crossing number of a graph $G$ is the least number of crossings over all possible drawings of $G$. We present a structural characterization of graphs with crossing number one.
The Surface Topography of a Magnetic Fluid -- a Quantitative Comparison between Experiment and Numerical SimulationApr 05 2006Jul 20 2006The normal field instability in magnetic liquids is investigated experimentally by means of a radioscopic technique which allows a precise measurement of the surface topography. The dependence of the topography on the magnetic field is compared to results ... More
Graphs with at most one crossingJan 28 2019The crossing number of a graph $G$ is the least number of crossings over all possible drawings of $G$. We present a structural characterization of graphs with crossing number one.
Evidence for Superconducting Phase Coherence in the Metallic/Insulating Regime of the LaAlO3-SrTiO3 Interface Electron SystemDec 18 2015A superconducting phase with an extremely low carrier density of the order of 10^13 cm^-2 is present at LaAlO3-SrTiO3 interfaces. If depleted from charge carriers by means of a gate field, this superconducting phase undergoes a transition into a metallic/insulating ... More
Large Negative Electronic Compressibility of LaAlO3-SrTiO3 Interfaces with Ultrathin LaAlO3 LayersJul 27 2012A two-dimensional electron liquid is formed at the n-type interface between SrTiO3 and LaAlO3. Here we report on Kelvin probe microscopy measurements of the electronic compressibility of this electron system. The electronic compressibility is found to ... More
Response of a ferrofluid to traveling-stripe forcingMar 20 2008We observe the dynamics of waves propagating on the surface of a ferrofluid under the influence of a spatially and temporarily modulated field. In particular, we excite plane waves by a travelling lamellar modulation of the magnetization. By this external ... More
The Milky Way halo as a QSO absorption-line system. New results from an HST/STIS absorption-line catalogue of Galactic high-velocity cloudsJan 07 2013We use archival UV absorption-line data from HST/STIS to statistically analyse the absorption characteristics of the high-velocity clouds (HVCs) in the Galactic halo towards more than 40 extragalactic background sources. We determine absorption covering ... More
A Symbiotic Scenario for the Rapid Formation of Supermassive Black HolesNov 17 2006The most massive black holes, lurking at the centers of large galaxies, must have formed less than a billion years after the big bang, as they are visible today in the form of bright quasars at redshift larger than six. Their early appearance is mysterious, ... More
Locally enhanced conductivity due to the tetragonal domain structure in LaAlO$_{3}$/SrTiO$_{3}$ heterointerfacesDec 11 2013The ability to control materials properties through interface engineering is demonstrated by the appearance of conductivity at the interface of certain insulators, most famously the {001} interface of the band insulators LaAlO$_{3}$ and TiO$_{2}$-terminated ... More
On the implementation of a locally modified finite element method for interface problems in deal.IIJun 04 2018In this work, we describe a simple finite element approach that is able to resolve weak discontinuities in interface problems accurately. The approach is based on a fixed patch mesh consisting of quadrilaterals, that will stay unchanged independent of ... More
Modeling specific action potentials in the human atria based on a minimal reaction-diffusion modelSep 05 2017We present an effective method to model empirical action potentials of specific patients in the human atria based on the minimal model of Bueno-Orovio, Cherry and Fenton adapted to atrial electrophysiology. In this model, three ionic are currents introduced, ... More
Factorisations and characterisations of induced-hereditary and compositive propertiesAug 05 2003A graph property (i.e., a set of graphs) is induced-hereditary or additive if it is closed under taking induced-subgraphs or disjoint unions. If $\cP$ and $\cQ$ are properties, the product $\cP \circ \cQ$ consists of all graphs $G$ for which there is ... More
Partial Fermionization---Spectral Universality in 1D Repulsive Bose GasesFeb 22 2019Due to the vast growth of the many-body level density with excitation energy, its smoothed form is of central relevance for spectral and thermodynamic properties of interacting quantum systems. We compute the cumulative of this level density for confined ... More
Uniqueness of circumcenters in generalized Minkowski spacesMar 28 2018Apr 04 2018In an $n$-dimensional normed space every bounded set has a unique circumball if and only if every set of cardinality two has a unique circumball and if and only if the unit ball of the space is strictly convex. When the symmetry of the norm is dropped, ... More
OpenCL 2.0 for FPGAs using OCLAccAug 28 2015Designing hardware is a time-consuming and complex process. Realization of both, embedded and high-performance applications can benefit from a design process on a higher level of abstraction. This helps to reduce development time and allows to iteratively ... More
A multi-instance deep neural network classifier: application to Higgs boson CP measurementMar 02 2018Sep 06 2018We investigate properties of a classifier applied to the measurements of the CP state of the Higgs boson in $H\rightarrow\tau\tau$ decays. The problem is framed as binary classifier applied to individual instances. Then the prior knowledge that the instances ... More
Ball Convex Bodies in Minkowski SpacesMar 07 2016The notion of ball convexity, considered in finite dimensional real Banach spaces, is a natural and useful extension of usual convexity; one replaces intersections of half-spaces by suitable intersections of balls. A subset $S$ of a normed space is called ... More
The locally adapted patch finite element method for interface problems on triangular meshesSep 30 2016Nov 15 2016We present a locally adapted parametric finite element method for interface problems. For this adapted finite element method we show optimal convergence for elliptic interface problems with a discontinuous diffusion parameter. The method is based on the ... More
A proof of a sumset conjecture of ErdősMar 01 2018Jun 13 2019In this paper we show that every set $A \subset \mathbb{N}$ with positive density contains $B+C$ for some pair $B,C$ of infinite subsets of $\mathbb{N}$, settling a conjecture of Erd\H{o}s. The proof features two different decompositions of an arbitrary ... More
Multiple origins for the DLA at $z_\mathrm{abs}=0.313$ toward PKS 1127$-$145 indicated by a complex dust depletion pattern of Ca, Ti, and MnSep 20 2017We investigate the dust depletion properties of optically thick gas in and around galaxies and its origin we study in detail the dust depletion patterns of Ti, Mn, and Ca in the multi-component damped Lyman-$\alpha$ (DLA) absorber at $z_\mathrm{abs}=0.313$ ... More
Ore extensions for function algebrasFeb 12 2019Feb 15 2019In this article we consider the Ore extension Algebra for the algebra $\mathcal{A}$ of functions with finite support on a countable set. We derive explicit formulas for twisted derivations on $\mathcal{A}.$ We give a description for the centralizer of ... More