Results for "Sören Dörscher"

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Noise and instability of an optical lattice clockJul 17 2015Nov 03 2015We present an analysis of the different types of noise from the detection and interrogation laser in our strontium lattice clock. We develop a noise model showing that in our setup quantum projection noise--limited detection is possible if more than 130~atoms ... More
Lattice-induced photon scattering in an optical lattice clockFeb 08 2018Jul 19 2018We investigate scattering of lattice laser radiation in a strontium optical lattice clock and its implications for operating clocks at interrogation times up to several tens of seconds. Rayleigh scattering does not cause significant decoherence of the ... More
Lattice-induced photon scattering in an optical lattice clockFeb 08 2018We investigate scattering of lattice laser radiation in a strontium optical lattice clock and its implications for operating clocks at interrogation times up to several ten seconds. Rayleigh scattering does not cause significant decoherence of the atomic ... More
Optimal decision under ambiguity for diffusion processesOct 18 2011Oct 18 2012In this paper we consider stochastic optimization problems for an ambiguity averse decision maker who is uncertain about the parameters of the underlying process. In a first part we consider problems of optimal stopping under drift ambiguity for one-dimensional ... More
Hartree Corrections in a Mean-field Limit for Fermions with Coulomb InteractionSep 15 2016May 24 2017We consider the many-body dynamics of fermions with Coulomb interaction in a mean-field scaling limit where the kinetic and potential energy are of the same order for large particle numbers. In the considered limit the spatial variation of the mean-field ... More
Phasetype distributions, autoregressive processes and overshootAug 04 2010Autoregressive processes are intensively studied in statistics and other fields of applied stochastics. For many applications the overshoot and the threshold-time are of special interest. When the upward innovations are in the class of phasetype distributions ... More
An Application of Periodic Unfolding on ManifoldsJun 10 2013We show how the newly developed method of Periodic Unfolding on Riemannian manifolds can be applied to PDE problems: We consider the homogenization of an elliptic model problem. In the limit, we obtain a generalization of the well-known limit- and cell-problem. ... More
Radial multipliers on amalgamated free products of II_1-factorsJun 24 2013Dec 18 2013Let $\mathcal{M}_i$ be a family of $\mathrm{II}_1$-factors, containing a common $\mathrm{II}_1$-subfactor $\mathcal{N}$, such that $[\mathcal{M}_i:\mathcal{N}] \in \mathbb{N}_0$ for all $i$. Furthermore, let $\phi \colon \mathbb{N}_0 \to \mathbb{C}$. ... More
Finite element simulation of nonlinear bending models for thin elastic rods and platesJan 28 2019Nonlinear bending phenomena of thin elastic structures arise in various modern and classical applications. Characterizing low energy states of elastic rods has been investigated by Bernoulli in 1738 and related models are used to determine configurations ... More
Geometric Set Cover and Hitting Sets for Polytopes in $R^3$Feb 20 2008Suppose we are given a finite set of points $P$ in $\R^3$ and a collection of polytopes $\mathcal{T}$ that are all translates of the same polytope $T$. We consider two problems in this paper. The first is the set cover problem where we want to select ... More
Gott time machines in the Anti-de Sitter spaceJan 12 1995In 1991 Gott presented a solution of Einstein's field equations in 2+1 dimensions with $\Lambda = 0$ that contained closed timelike curves (CTC's). This solution was remarkable because at first it did not seem to be unphysical in any other respect. Later, ... More
Hartree-Fock Corrections in a Mean-field Limit for FermionsSep 15 2016We consider the many-body dynamics of fermions with Coulomb interaction in a mean-field scaling limit where the kinetic and potential energy are of the same order for large particle numbers. In the considered limit the spatial variation of the mean-field ... More
Generalized Fibonacci Numbers and Blackwell's Renewal TheoremDec 22 2010We investigate a connection between generalized Fibonacci numbers and renewal theory for stochastic processes. Using Blackwell's renewal theorem we find an approximation to the generalized Fibonacci numbers. With the help of error estimates in the renewal ... More
On the Beavers-Joseph-Saffman boundary condition for curved interfacesApr 22 2015The appropriate boundary condition between an unconfined incompressible viscous fluid and a porous medium is given by the law of Beavers and Joseph. The latter has been justified both experimentally and mathematically, using the method of periodic homogenisation. ... More
Barbero's Hamiltonian derived from a generalized Hilbert-Palatini actionNov 07 1995Barbero recently suggested a modification of Ashtekar's choice of canonical variables for general relativity. Although leading to a more complicated Hamiltonian constraint this modified version, in which the configuration variable still is a connection, ... More
On the Solution of General Impulse Control Problems Using Superharmonic FunctionsApr 12 2013Sep 19 2013In this paper, a characterization of the solution of impulse control problems in terms of superharmonic functions is given. In a general Markovian framework, the value function of the impulse control problem is shown to be the minimal function in a convex ... More
Generic steady state bifurcations in monoid equivariant dynamics with applications in homogeneous coupled cell systemsFeb 23 2018Oct 09 2018We prove that steady state bifurcations in finite-dimensional dynamical systems that are symmetric with respect to a monoid representation generically occur along an absolutely indecomposable subrepresentation. This is stated as a conjecture in B. Rink ... More
A method for pricing American options using semi-infinite linear programmingMar 23 2011Jun 09 2011We introduce a new approach for the numerical pricing of American options. The main idea is to choose a finite number of suitable excessive functions (randomly) and to find the smallest majorant of the gain function in the span of these functions. The ... More
Creation of Quantum-Degenerate Gases of Ytterbium in a Compact 2D-/3D-MOT SetupMar 05 2013We report on the first experimental setup based on a 2D-/3D-MOT scheme to create both Bose-Einstein condensates and degenerate Fermi gases of several ytterbium isotopes. Our setup does not require a Zeeman slower and offers the flexibility to simultaneously ... More
Distributed Convex Optimization with Many Convex ConstraintsOct 07 2016We address the problem of solving convex optimization problems with many convex constraints in a distributed setting. Our approach is based on an extension of the alternating direction method of multipliers (ADMM) that recently gained a lot of attention ... More
Collectivity in small collision systems : an initial state perspectiveNov 01 2016Measurements of multi-particle correlations in the collisions of small systems such as $p+p$, $p/d/^3He+A$ show striking similarity to the observations in heavy ion collisions. A number of observables measured in the high multiplicity events of these ... More
Impulse control and expected supremaMar 04 2015Nov 04 2015We consider a class of impulse control problems for general underlying strong Markov processes on the real line, which allows for an explicit solution. The optimal impulse times are shown to be of threshold type and the optimal threshold is characterized ... More
A General Method for Finding the Optimal Threshold in Discrete TimeOct 23 2017Oct 26 2018We develop an approach for solving one-sided optimal stopping problems in discrete time for general underlying Markov processes on the real line. The main idea is to transform the problem into an auxiliary problem for the ladder height variables. In case ... More
Equivariant bifurcations in $4$-dimensional fixed point spacesNov 02 2015Jul 11 2016In this paper we continue the study of group representations which are counterexamples to the Ize conjecture. As in the previous papers by Lauterbach [14] and Lauterbach & Matthews [15] we find new infinite series of finite groups leading to such counterexamples. ... More
The Monotone Case Approach for the Solution of Certain Multidimensional Optimal Stopping ProblemsMay 04 2017Jun 03 2019This paper studies explicitly solvable multidimensional optimal stopping problems of sum- and product-type in discrete and continuous time using the monotone case approach. It gives a review on monotone case stopping using the Doob decomposition, resp. ... More
Mean-field Dynamics for the Nelson Model with FermionsJul 18 2018Feb 24 2019The Nelson model (with ultraviolet cutoff) describes a quantum system of non-relativistic particles coupled to a positive or zero mass quantized scalar field. We take the non-relativistic particles to obey Fermi statistics and discuss the time evolution ... More
Primal-dual gap estimators for a posteriori error analysis of nonsmooth minimization problemsFeb 11 2019The primal-dual gap is a natural upper bound for the energy error and, for uniformly convex minimization problems, also for the error in the energy norm. This feature can be used to construct reliable primal-dual gap error estimators for which the constant ... More
Branching within branching II: Limit theoremsMay 15 2015This continues work started in part I on a general branching-within-branching model for host-parasite co-evolution. Here we focus on asymptotic results for relevant processes in the case when parasites survive. In particular, limit theorems for the processes ... More
The law of large numbers for the free multiplicative convolutionNov 19 2012Apr 08 2013In classical probability the law of large numbers for the multiplicative convolution follows directly from the law for the additive convolution. In free probability this is not the case. The free additive law was proved by D. Voiculescu in 1986 for probability ... More
Radial multipliers on reduced free products of operator algebrasJan 03 2012Jan 04 2012Let A_i be a family of unital C*-algebras, respectively, of von Neumann algebras and phi: N_0 \to C. We show that if a Hankel matrix related to phi is trace-class, then there exists a unique completely bounded map M_phi on the reduced free product of ... More
Error bounds for discretized optimal transport and its reliable efficient numerical solutionOct 13 2017The discretization of optimal transport problems often leads to large linear programs with sparse solutions. We derive error estimates for the approximation of the problem using convex combinations of Dirac measures and devise an active-set strategy that ... More
Dirac and Laplace operators on some non-orientable conformally flat manifoldsFeb 21 2011In this paper we present an explicit construction for the fundamental solution to the Dirac and Laplace operator on some non-orientable conformally flat manifolds. We first treat a class of projective cylinders and tori where we can study monogenic sections ... More
Optimal relaxed portfolio strategies for growth rate maximization problems with transaction costsSep 03 2012Jun 07 2013In this paper we investigate a new class of growth rate maximization problems based on impulse control strategies such that the average number of trades per time unit does not exceed a fixed level. Moreover, we include proportional transaction costs to ... More
Twisted superfluid phase in the extended one-dimensional Bose-Hubbard modelMay 17 2016Jul 21 2016In one-dimensional systems a twisted superfluid phase is found which is induced by a spontaneous breaking of the time-reversal symmetry. Using the density-matrix renormalization group allows us to show that the excitation energy gap closes exponentially ... More
Ferromagnetism and non-local correlations in the Hubbard modelMar 08 2012We study the possibility and stability of band-ferromagnetism in the single-band Hubbard model for the simple cubic (SC) lattice. A non-local self-energy is derived within a modified perturbation theory. Results for the spectral density and quasiparticle ... More
Incrementally Building Topology Graphs via Distance MapsNov 05 2018Mapping is an essential task for mobile robots and topological representation often works as a basis for the various applications. In this paper, a novel framework that can build topological maps incrementally is proposed. The algorithm is based on distance ... More
Resolvent-Techniques For Multiple Exercise ProblemsSep 27 2013We study optimal multiple stopping of strong Markov processes with random refraction periods. The refraction periods are assumed to be exponentially distributed with a common rate and independent of the underlying dynamics. Our main tool is using the ... More
Hypergeometric continuation of divergent perturbation series. I. Critical exponents of the Bose-Hubbard modelMar 13 2018We study the connection between the exponent of the order parameter of the Mott insulator-to-superfluid transition occurring in the two-dimensional Bose-Hubbard model, and the divergence exponents of its one- and two-particle correlation functions. We ... More
Incrementally Building Topology Graphs via Distance MapsNov 05 2018May 08 2019Mapping is an essential task for mobile robots and topological representation often works as a basis for the various applications. In this paper, a novel framework that can build topological maps incrementally is proposed. The algorithm is using a distance ... More
Branching within branching I: The extinction problemMay 15 2015We consider a discrete-time host-parasite model for a population of cells which are colonized by proliferating parasites. The cell population grows like an ordinary Galton-Watson process, but in reflection of real biological settings the multiplication ... More
A host-parasite model for a two-type cell populationApr 02 2012Feb 05 2013A host-parasite model is considered for a population of cells that can be of two types, A or B, and exhibits unilateral reproduction: while a B-cell always splits into two cells of the same type, the two daughter cells of an A-cell can be of any type. ... More
On time-inconsistent stopping problems and mixed strategy stopping timesApr 19 2018May 07 2018A game-theoretic framework for time-inconsistent stopping problems where the time-inconsistency is due to the consideration of a non-linear function of an expected reward is developed. A class of mixed strategy stopping times that allows the agents in ... More
On Finding Equilibrium Stopping Times for Time-Inconsistent Markovian ProblemsSep 15 2017Dec 04 2018Standard Markovian optimal stopping problems are consistent in the sense that the first entrance time into the stopping set is optimal for each initial state of the process. Clearly, the usual concept of optimality cannot in a straightforward way be applied ... More
Hypergeometric continuation of divergent perturbation series. II. Comparison with Shanks transformation and Padé approximationMar 13 2018We explore in detail how analytic continuation of divergent perturbation series by generalized hypergeometric functions is achieved in practice. Using the example of strong-coupling perturbation series provided by the two-dimensional Bose-Hubbard model, ... More
Heterogeneous Multi-sensor Calibration based on Graph OptimizationMay 27 2019Many robotics and mapping systems contain multiple sensors to perceive the environment. Extrinsic parameter calibration, the identification of the position and rotation transform between the frames of the different sensors, is critical to fuse data from ... More
Automorphic Forms and Dirac Operators on Conformally Flat ManifoldsApr 12 2018In this paper we present a summarizing description of the connection between Dirac operators on conformally flat manifolds and automorphic forms based on a series of joint work with John Ryan over the last fifteen years. We also outline applications to ... More
Numerical approximation of optimal convex shapesOct 25 2018This article investigates the numerical approximation of shape optimization problems with PDE constraint on classes of convex domains. The convexity constraint provides a compactness property which implies well posedness of the problem. Moreover, we prove ... More
An Elementary Method for the Explicit Solution of Multidimensional Optimal Stopping ProblemsMay 04 2017We study explicitly solvable multidimensional optimal stopping problems. Our approach is based on the notion of monotone stopping problems in discrete and continuous time. The method is illustrated with a variety of examples including multidimensional ... More
Convergence of switching diffusionsMar 04 2014Nov 26 2014This paper studies the asymptotic behavior of processes with switching. More precisely, the stability under fast switching for diffusion processes and discrete state space Markovian processes is considered. The proofs are based on semimartingale techniques, ... More
Evacuating Two Robots from a Disk: A Second CutMay 25 2019We present an improved algorithm for the problem of evacuating two robots from the unit disk via an unknown exit on the boundary. Robots start at the center of the disk, move at unit speed, and can only communicate locally. Our algorithm improves previous ... More
Convergence of fully discrete implicit and semi-implicit approximations of nonlinear parabolic equationsFeb 21 2019The article addresses the convergence of implicit and semi-implicit, fully discrete approximations of a class of nonlinear parabolic evolution problems. Such schemes are popular in the numerical solution of evolutions defined with the $p$-Laplace operator ... More
A New Method and a New Scaling For Deriving Fermionic Mean-field DynamicsSep 01 2014Jan 11 2016We introduce a new method for deriving the time-dependent Hartree or Hartree-Fock equations as an effective mean-field dynamics from the microscopic Schroedinger equation for fermionic many-particle systems in quantum mechanics. The method is an adaption ... More
A high-performance optical lattice clock based on bosonic atomsMar 08 2018Optical lattice clocks with uncertainty and instability in the $10^{-17}$-range and below have so far been demonstrated exclusively using fermions. Here, we demonstrate a bosonic optical lattice clock with $3\times 10^{-18}$ instability and $2.0\times ... More
Notes on the Cluster Gutzwiller Method: Inhomogeneous Lattices, Excitations, and Cluster Time EvolutionAug 09 2016Several perspectives of the cluster Gutzwiller method are briefly discussed. I show that the cluster mean-field method can be used for large inhomogeneous lattices, for computing local excitations, and for the time evolution of correlated quantum systems. ... More
Alternating direction method of multipliers with variable step sizesApr 20 2017The alternating direction method of multipliers (ADMM) is a flexible method to solve a large class of convex minimization problems. Particular features are its unconditional convergence with respect to the involved step size and its direct applicability. ... More
Distributed Convex Optimization with Many Convex ConstraintsOct 07 2016Apr 06 2018We address the problem of solving convex optimization problems with many convex constraints in a distributed setting. Our approach is based on an extension of the alternating direction method of multipliers (ADMM) that recently gained a lot of attention ... More
Riesz representation and optimal stopping with two case studiesSep 10 2013Oct 20 2015In this paper we demonstrate that the Riesz representation of excessive functions is a useful and enlightening tool to study optimal stopping problems. After a short general discussion of the Riesz representation we concretize, firstly, on a d-dimensional ... More
Extrinsic curvature of codimension one isometric immersions with Hölder continuous derivativesJan 22 2016Sep 14 2016We prove that if $n$ is even, $(M,g)$ is a compact $n$-dimensional Riemannian manifold whose Pfaffian form is a positive multiple of the volume form, and $y\in C^{1,\alpha}(M;\mathbb{R}^{n+1})$ is an isometric immersion with $n/(n+1)< \alpha\leq 1$, then ... More
Numerical solution of a nonlinear eigenvalue problem arising in optimal insulationAug 12 2017The optimal insulation of a heat conducting body by a thin film of variable thickness can be formulated as a nondifferentiable, nonlocal eigenvalue problem. The discretization and iterative solution for the reliable computation of corresponding eigenfunctions ... More
Anscombe's Model for Sequential Clinical Trials RevisitedDec 15 2017In Anscombe's classical model, the objective is to find the optimal sequential rule for learning about the difference between two alternative treatments and subsequently selecting the superior one. The population for which the procedure is optimised has ... More
XYZ at BelleMay 20 2019Recent results of exotic states with heavy quarks, denoted as $XYZ$ states, are presented. The results include searches for the $Y$(4260) in $B$ meson decays, a spin partner of $Y$(4630), and the strange Pentaquark $P_s^+$. In addition, the measurements ... More
Spectral approximation of fractional PDEs in image processing and phase field modelingApr 02 2017Aug 23 2017Fractional differential operators provide an attractive mathematical tool to model effects with limited regularity properties. Particular examples are image processing and phase field models in which jumps across lower dimensional subsets and sharp transitions ... More
Stability of a simple scheme for the approximation of elastic knots and self-avoiding inextensible curvesApr 06 2018We discuss a semi-implicit numerical scheme that allows for minimizing the bending energy of curves within certain isotopy classes. To this end we consider a weighted sum of the bending energy and the tangent-point functional. Based on estimates for the ... More
Musical Instrument Separation on Shift-Invariant Spectrograms via Stochastic Dictionary LearningJun 01 2018Aug 02 2018We propose a novel method for the blind separation of audio signals produced by musical instruments. While the approach of applying non-negative matrix factorization (NMF) has been studied in many papers, it does not make use of the pitch-invariance that ... More
Dimerized Mott insulators in hexagonal optical latticesApr 07 2014Sep 10 2014We study bosonic atoms in optical honeycomb lattices with anisotropic tunneling and find dimerized Mott insulator phases with fractional filling. These incompressible insulating phases are characterized by an interaction-driven localization of particles ... More
Lattice point inequalities for centered convex bodiesMay 24 2015We study upper bounds on the number of lattice points for convex bodies having their centroid at the origin. For the family of simplices as well as in the planar case we obtain best possible results. For arbitrary convex bodies we provide an upper bound, ... More
On a discrete John-type theoremApr 10 2019As a discrete counterpart to the classical John theorem on the approximation of (symmetric) $n$-dimensional convex bodies $K$ by ellipsoids, Tao and Vu introduced so called generalized arithmetic progressions $P(A,b)\subset Z^n$ in order to cover (many ... More
Azimuthal anisotropies in p+Pb collisions from classical Yang-Mills dynamicsFeb 04 2015May 27 2015We compute single and double inclusive gluon distributions in classical Yang-Mills simulations of proton-lead collisions and extract the associated transverse momentum dependent Fourier harmonics $v_2(p_T)$ and $v_3(p_T)$. Gluons have a large $v_2$ in ... More
Space-Time Picture of Baryon Stopping in the Color-Glass CondensateNov 09 2018Nov 28 2018We discuss baryon stopping in the Color Glass Condensate description of high energy scattering. We consider the scattering of a distribution of valence quarks on an ultra-relativistic sheet of colored charge. We compute the distribution of scattered quarks ... More
Singular Values for ReLU LayersDec 06 2018Despite their prevalence in neural networks we still lack a thorough theoretical characterization of ReLU layers. This paper aims to further our understanding of ReLU layers by studying how the activation function ReLU interacts with the linear component ... More
Classics Illustrated: Limits of SpacetimesJun 17 2014Oct 06 2014We carefully study the $e \rightarrow m$ and $e \rightarrow 0$ limits of the Reissner-Nordstr\"om spacetime using Geroch's definition of limits of spacetimes. This is implemented by embedding the one-parameter family of spacetimes in anti-de Sitter space, ... More
Budget-restricted utility games with ordered strategic decisionsJul 11 2014We introduce the concept of budget games. Players choose a set of tasks and each task has a certain demand on every resource in the game. Each resource has a budget. If the budget is not enough to satisfy the sum of all demands, it has to be shared between ... More
GENO -- GENeric Optimization for Classical Machine LearningMay 31 2019Although optimization is the longstanding algorithmic backbone of machine learning, new models still require the time-consuming implementation of new solvers. As a result, there are thousands of implementations of optimization algorithms for machine learning ... More
Classification error in multiclass discrimination from Markov dataSep 22 2015As a model for an on-line classification setting we consider a stochastic process $(X_{-n},Y_{-n})_{n}$, the present time-point being denoted by 0, with observables $ \ldots,X_{-n},X_{-n+1},\ldots, X_{-1}, X_0$ from which the pattern $Y_0$ is to be inferred. ... More
Unconditional stability of semi-implicit discretizations of singular flowsNov 29 2017A popular and efficient discretization of evolutions involving the singular $p$-Laplace operator is based on a factorization of the differential operator into a linear part which is treated implicitly and a regularized singular factor which is treated ... More
A new algorithm for computing idempotents of R-trivial monoidsJun 06 2019The authors of [Primitive orthogonal idempotents for R-trivial monoids, Journal of Algebra] provide an algorithm for finding a complete system of primitive orthogonal idempotents for CM, where M is any finite R-trivial monoid. Their method relies on a ... More
Odd cycles in subgraphs of sparse pseudorandom graphsJun 12 2019We answer two extremal questions about odd cycles that naturally arise in the study of sparse pseudorandom graphs. Let $\Gamma$ be an $(n,d,\lambda)$-graph, i.e., $n$-vertex, $d$-regular graphs with all nontrivial eigenvalues in the interval $[-\lambda,\lambda]$. ... More
Emulating Molecular Orbitals and Electronic Dynamics with Ultracold AtomsMar 20 2015Nov 23 2015In recent years, ultracold atoms in optical lattices have proven their great value as quantum simulators for studying strongly correlated phases and complex phenomena in solid-state systems. Here we reveal their potential as quantum simulators for molecular ... More
Nonlinear amplification of instabilities with longitudinal expansionJan 17 2012We study the dynamics of nonequilibrium instabilities in anisotropically expanding systems. The most prominent example of such a system is the 'Glasma' in the context of relativistic heavy-ion collision experiments, where the expansion is a consequence ... More
Results on Charmonium and Charmonium-like States at the Belle ExperimentSep 08 2011New results of the Belle experiment at the KEKB asymmetric e^+e^- collider are presented, in particular (a) measurement of the mass and width of the $\eta_c$ and $\eta_c'$ in B meson decays, (b) measurement of the mass, width and quantum numbers of the ... More
Results on Charmonium(-like) and Bottomonium(-like) States from Belle and BaBarOct 12 2010Spectroscopy results for Belle and BaBar are reported. A particular focus is put on new results of the X(3872) state with its radiative decays to $J$/$\psi$$\gamma$ and $\psi'$$\gamma$, its decay into $J$/$\psi$3$\pi$ and the search for production in ... More
Optimal multiple stopping with random waiting timesMay 09 2012In the standard models for optimal multiple stopping problems it is assumed that between two exercises there is always a time period of deterministic length $\delta$, the so called refraction period. This prevents the optimal exercise times from bunching ... More
Designing a Roadside Sensor Infrastructure to Support Automated DrivingFeb 15 2019Automation of complex traffic scenarios is expected to rely on input from a roadside infrastructure to complement the vehicles' environment perception. We here explore design requirements for a prototypical setup of virtual vision or RADAR sensors along ... More
Optimal stopping of strong Markov processesMar 21 2012Apr 02 2012We characterize the value function and the optimal stopping time for a large class of optimal stopping problems where the underlying process to be stopped is a fairly general Markov process. The main result is inspired by recent findings for L\'evy processes ... More
Ehrhart tensor polynomialsJun 06 2017The notion of Ehrhart tensor polynomials, a natural generalization of the Ehrhart polynomial of a lattice polytope, was recently introduced by Ludwig and Silverstein. We initiate a study of their coefficients. In the vector and matrix cases, we give Pick-type ... More
Exotics: Heavy Pentaquarks and TetraquarksJun 02 2017Jul 27 2017For many decades after the invention of the quark model in 1964 there was no evidence that hadrons are formed from anything other than the simplest pairings of quarks and antiquarks, mesons being formed of a quark-antiquark pair and baryons from three ... More
A Solvable Two-dimensional Optimal Stopping Problem in the Presence of AmbiguityMay 14 2019According to conventional wisdom, ambiguity accelerates optimal timing by decreasing the value of waiting in comparison with the unambiguous benchmark case. We study this mechanism in a multidimensional setting and show that in a multifactor model ambiguity ... More
Derivation of the Bogoliubov Time Evolution for Gases with Finite Speed of SoundNov 05 2017The derivation of mean-field limits for quantum systems at zero temperature has attracted many researchers in the last decades. Recent developments are the consideration of pair correlations in the effective description, which lead to a much more precise ... More
Oscillations and interactions of dark and dark-bright solitons in Bose-Einstein condensatesApr 03 2008Solitons are among the most distinguishing fundamental excitations in a wide range of non-linear systems such as water in narrow channels, high speed optical communication, molecular biology and astrophysics. Stabilized by a balance between spreading ... More
Representing Dataset Quality Metadata using Multi-Dimensional ViewsAug 11 2014Data quality is commonly defined as fitness for use. The problem of identifying quality of data is faced by many data consumers. Data publishers often do not have the means to identify quality problems in their data. To make the task for both stakeholders ... More
Luzzu - A Framework for Linked Data Quality AssessmentDec 11 2014Jan 07 2016With the increasing adoption and growth of the Linked Open Data cloud [9], with RDFa, Microformats and other ways of embedding data into ordinary Web pages, and with initiatives such as, the Web is currently being complemented with a Web of ... More
OpenCourseWare Observatory -- Does the Quality of OpenCourseWare Live up to its Promise?Oct 21 2014Apr 14 2015A vast amount of OpenCourseWare (OCW) is meanwhile being published online to make educational content accessible to larger audiences. The awareness of such courses among users and the popularity of systems providing such courses are increasing. However, ... More
Improved Bounds and Schemes for the Declustering ProblemMar 02 2006The declustering problem is to allocate given data on parallel working storage devices in such a manner that typical requests find their data evenly distributed on the devices. Using deep results from discrepancy theory, we improve previous work of several ... More
Some applications of parabolic Dirac operators to the instationary Navier-Stokes problem on conformally flat cylinders and tori in $\mathbb{R}^3$Apr 05 2018In this paper we give a survey on how to apply recent techniques of Clifford analysis over conformally flat manifolds to deal with instationary flow problems on cylinders and tori. Solutions are represented in terms of integral operators involving explicit ... More
Remarks on Kneip's linear smoothersMay 07 2014We were trying to understand the analysis provided by Kneip (1994, Ordered Linear Smoothers). In particular we wanted to persuade ourselves that his results imply the oracle inequality stated by Tsybakov (2014, Lecture 8). This note contains our reworking ... More
Optimal portfolio selection under vanishing fixed transaction costsNov 04 2016In this paper, asymptotic results in a long-term growth rate portfolio optimization model under both fixed and proportional transaction costs are obtained. More precisely, the convergence of the model when the fixed costs tend to zero is investigated. ... More
Luzzu Quality Metric Language -- A DSL for Linked Data Quality AssessmentApr 29 2015The steadily growing number of linked open datasets brought about a number of reservations amongst data consumers with regard to the datasets' quality. Quality assessment requires significant effort and consideration, including the definition of data ... More
Hypergeometric analytic continuation of the strong-coupling perturbation series for the 2d Bose-Hubbard modelMar 13 2015Aug 04 2015We develop a scheme for analytic continuation of the strong-coupling perturbation series of the pure Bose-Hubbard model beyond the Mott insulator-to-superfluid transition at zero temperature, based on hypergeometric functions and their generalizations. ... More
A Tight Approximation for Fully Dynamic Bin Packing without BundlingNov 03 2017May 24 2018We consider a variant of the classical Bin Packing Problem, called Fully Dynamic Bin Packing. In this variant, items of a size in $(0,1]$ must be packed in bins of unit size. In each time step, an item either arrives or departs from the packing. An algorithm ... More
Wind Turbine Model and Observer in Takagi-Sugeno Model StructureJan 31 2014Based on a reduced-order, dynamic nonlinear wind turbine model in Takagi-Sugeno (TS) model structure, a TS state observer is designed as a disturbance observer to estimate the unknown effective wind speed. The TS observer model is an exact representation ... More