Results for "Magnus T. Koudahl"

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Asynchronous Multi-Agent Primal-Dual OptimizationJun 07 2016We present a framework for asynchronously solving nonlinear optimization problems over networks of agents which are augmented by the presence of a centralized cloud computer. This framework uses a Tikhonov-regularized primal-dual approach in which the ... More
A Reinforcement Learning Framework for Sequencing Multi-Robot BehaviorsSep 12 2019Sep 13 2019Given a list of behaviors and associated parameterized controllers for solving different individual tasks, we study the problem of selecting an optimal sequence of coordinated behaviors in multi-robot systems for completing a given mission, which could ... More
Ergodicity-breaking reveals time optimal economic behavior in humansJun 11 2019Jun 12 2019Ergodicity describes an equivalence between the expectation value and the time average of observables. Applied to human behaviour, ergodic theory reveals how individuals should tolerate risk in different environments. To optimise wealth over time, agents ... More
Ergodicity-breaking reveals time optimal economic behavior in humansJun 11 2019Ergodicity describes an equivalence between the expectation value and the time average of observables. Applied to human behaviour, ergodic theory reveals how individuals should tolerate risk in different environments. To optimise wealth over time, agents ... More
Ergodicity-breaking reveals time optimal economic behavior in humansJun 11 2019Jun 19 2019Ergodicity describes an equivalence between the expectation value and the time average of observables. Applied to human behaviour, ergodic theory reveals how individuals should tolerate risk in different environments. To optimise wealth over time, agents ... More
A Limited-Feedback Approximation Scheme for Optimal Switching Problems with Execution DelaysMay 02 2016Feb 14 2017We consider a type of optimal switching problems with non-uniform execution delays and ramping. Such problems frequently occur in the operation of economical and engineering systems. We first provide a solution to the problem by applying a probabilistic ... More
On the Finite Horizon Optimal Switching Problem with Random LagAug 24 2018Aug 21 2019We consider an optimal switching problem with random lag and possibility of component failure. The random lag is modeled by letting the operation mode follow a regime switching Markov-model with transition intensities that depend on the switching mode. ... More
A Finite Horizon Optimal Switching Problem with Memory and Application to Controlled SDDEsMay 22 2019We consider an optimal switching problem where the terminal reward depends on the entire control trajectory. We show existence of an optimal control by applying a probabilistic technique based on the concept of Snell envelopes. We then apply this result ... More
A Bayesian model selection approach for identifying differentially expressed transcripts from RNA-Seq dataDec 09 2014Sep 26 2016Recent advances in molecular biology allow the quantification of the transcriptome and scoring transcripts as differentially or equally expressed between two biological conditions. Although these two tasks are closely linked, the available inference methods ... More
Cancellation-Free Circuits in Unbounded and Bounded DepthMay 14 2013Oct 17 2014We study the notion of "cancellation-free" circuits. This is a restriction of linear Boolean circuits (XOR circuits), but can be considered as being equivalent to previously studied models of computation. The notion was coined by Boyar and Peralta in ... More
Time-Periodic Solutions of the Burgers EquationMay 03 2012We investigate the time periodic solutions to the viscous Burgers equation $u_t -\mu u_{xx} + uu_x = f$ for irregular forcing terms. We prove that the corresponding Burgers operator is a diffeomorphism between appropriate function spaces.
Inverse semigroup C*-algebras associated with left cancellative semigroupsFeb 27 2012Mar 09 2012To each discrete left cancellative semigroup $S$ one may associate a certain inverse semigroup $I_l(S)$, often called the left inverse hull of $S$. We show how the full and the reduced C*-algebras of $I_l(S)$ are related to the full and reduced semigroup ... More
Simplified a priori Estimate for the Time Periodic Burgers' EquationMay 03 2012We present here a version of the existence and uniqueness result of time periodic solutions to the viscous Burgers equation with irregular forcing terms (with Sobolev regularity -1 in space). The key result here is an a priori estimate which is simpler ... More
Thermodynamic stability of droplets, bubbles and thick films in open and closed poresSep 03 2019A fluid in a pore can form diverse heterogeneous structures. We combine a capillary description with the cubic-plus-association equation of state to study the thermodynamic stability of droplets, bubbles and films of water at 358 K in a cylindrically ... More
Rapid mixing of subset Glauber dynamics on graphs of bounded tree-widthFeb 17 2011Motivated by the `subgraphs world' view of the ferromagnetic Ising model, we develop a general approach to studying mixing times of Glauber dynamics based on subset expansion expressions for a class of graph polynomials. With a canonical paths argument, ... More
On Fell bundles over inverse semigroups and their left regular representationsNov 09 2016We prove a version of Wordingham's theorem for left regular representations in the setting of Fell bundles of inverse semigroups and use this result to discuss the various associated cross sectional C*-algebras.
Empirical Big Data Research: A Systematic Literature MappingSep 10 2015Background: Big Data is a relatively new field of research and technology, and literature reports a wide variety of concepts labeled with Big Data. The maturity of a research field can be measured in the number of publications containing empirical results. ... More
Clusters of eigenvalues for the magnetic Laplacian with Robin conditionJun 04 2014We study the Schr\"{o}dinger operator with a constant magnetic field in the exterior of a compact domain in euclidean space. Functions in the domain of the operator are subject to a boundary condition of the third type (a magnetic Robin condition). In ... More
Manipulating the Mott lobes: optical lattice bosons coupled to an array of atomic quantum dotsJun 06 2018Dec 06 2018We analyze quantum phase transitions in a system of optical lattice bosons coupled to an array of atomic quantum dots, or pseudospins-1/2. The system parallels the Bose-Hubbard model with a single difference of the direct tunneling between the lattice ... More
Convergence Rate Estimates for Consensus over Random GraphsOct 21 2016Mar 21 2017Multi-agent coordination algorithms with randomized interactions have seen use in a variety of settings in the multi-agent systems literature. In some cases, these algorithms can be random by design, as in a gossip-like algorithm, and in other cases they ... More
Convergence Rate Estimates for Consensus over Random GraphsOct 21 2016Multi-agent coordination algorithms with randomized interactions have seen use in a variety of settings in the multi-agent systems literature. In some cases, these algorithms can be random by design, as in a gossip-like algorithm, and in other cases they ... More
Acyclicity in Edge-Colored GraphsJan 08 2016Sep 12 2016A walk $W$ in edge-colored graphs is called properly colored (PC) if every pair of consecutive edges in $W$ is of different color. We introduce and study five types of PC acyclicity in edge-colored graphs such that graphs of PC acyclicity of type $i$ ... More
CASAD: CAN-Aware Stealthy-Attack Detection for In-Vehicle NetworksSep 18 2019Nowadays, vehicles have complex in-vehicle networks (IVNs) with millions of lines of code controlling almost every function in the vehicle including safety-critical functions. It has recently been shown that IVNs are becoming increasingly vulnerable to ... More
Cloud-Based Centralized/Decentralized Multi-Agent Optimization with Communication DelaysAug 25 2015We present and analyze a computational hybrid architecture for performing multi-agent optimization. The optimization problems under consideration have convex objective and constraint functions with mild smoothness conditions imposed on them. For such ... More
Asynchronous Multi-Agent Primal-Dual OptimizationJun 07 2016Oct 13 2016We present a framework for asynchronously solving convex optimization problems over networks of agents which are augmented by the presence of a centralized cloud computer. This framework uses a Tikhonov-regularized primal-dual approach in which the agents ... More
Higher order finite difference schemes for the magnetic induction equationsFeb 02 2011We describe high order accurate and stable finite difference schemes for the initial-boundary value problem associated with the magnetic induction equations. These equations model the evolution of a magnetic field due to a given velocity field. The finite ... More
Constraint Learning for Control Tasks with Limited Duration Barrier FunctionsAug 26 2019Sep 05 2019When deploying autonomous agents in unstructured environments over sustained periods of time, adaptability and robustness oftentimes outweigh optimality as a primary consideration. In other words, safety and survivability constraints play a key role and ... More
Quantum limited particle sensing in optical tweezersJul 24 2009Particle sensing in optical tweezers systems provides information on the position, velocity and force of the specimen particles. The conventional quadrant detection scheme is applied ubiquitously in optical tweezers experiments to quantify these parameters. ... More
Recovering tree-child networks from shortest inter-taxa distance informationNov 24 2017Phylogenetic networks are a type of leaf-labelled, acyclic, directed graph used by biologists to represent the evolutionary history of species whose past includes reticulation events. A phylogenetic network is tree-child if each non-leaf vertex is the ... More
Beyond Gröbner Bases: Basis Selection for Minimal SolversMar 12 2018Many computer vision applications require robust estimation of the underlying geometry, in terms of camera motion and 3D structure of the scene. These robust methods often rely on running minimal solvers in a RANSAC framework. In this paper we show how ... More
A Limited-Feedback Approximation Scheme for Optimal Switching Problems with Execution DelaysMay 02 2016Sep 22 2016We consider a type of optimal switching problems with non-uniform execution delays and ramping. Such problems frequently occur in the operation of economical and engineering systems. We first provide a solution to the problem by applying a probabilistic ... More
On the Finite Horizon Optimal Switching Problem with Random LagAug 24 2018We consider an optimal switching problem with random lag and possibility of component failure. The random lag is modeled by letting the operation mode follow a regime switching Markov-model with transition intensities that depend on the switching mode. ... More
Directable Fuzzy and Nondeterministic AutomataSep 22 2017We study three notions of directability of fuzzy automata akin to the D1-, D2- and D3-directability of nondeterministic automata. Thus an input word $w$ of a fuzzy automaton is D1-directing if a fixed single state is reachable by $w$ from all states, ... More
Analytic formulas for topological degree of non-smooth mappings: the even-dimensional caseJun 20 2010Feb 09 2013Topological degrees of continuous mappings between manifolds of even dimension are studied in terms of index theory of pseudo-differential operators. The index formalism of non-commutative geometry is used to derive analytic integral formulas for the ... More
The Pimsner-Voiculescu sequence for coactions of compact Lie groupsApr 25 2010Mar 02 2011The Pimsner-Voiculescu sequence is generalized to a Pimsner-Voiculescu tower describing the $KK$-category equivariant with respect to coactions of a compact Lie group satisfying the Hodgkin condition. A dual Pimsner-Voiculescu tower is used to show that ... More
Khovanov's conjecture over Z[c]Aug 15 2003We disprove the conjecture of M. Khovanov (math.QA/9908171) on the functoriality of his link homology with polynomial coefficients. This is in contrast to the case of integer coefficients, where functoriality was proved in math.GT/0206303 .
Implementation of an Android Framework for USB storage access without root rightsNov 22 2017This bachelor thesis describes the implementation of an Android framework to access mass storage devices over the USB interface of a smartphone. First the basics of USB (i.e. interfaces, endpoints and USB On the go) and accessing USB devices via the official ... More
Monitoring of tritium purity during long-term circulation in the KATRIN test experiment LOOPINO using laser Raman spectroscopyAug 08 2012The gas circulation loop LOOPINO has been set up and commissioned at Tritium Laboratory Karlsruhe (TLK) to perform Raman measurements of circulating tritium mixtures under conditions similar to the inner loop system of the neutrino-mass experiment KATRIN, ... More
Tilting and Refined Donaldson-Thomas InvariantsMar 25 2013Mar 06 2014We study tilting for the heart A of the canonical t-structure of the finite-dimensional derived category of the Ginzburg algebra for a quiver with potential (Q,W). We give conditions on that the stable objects for a central charge on A define a sequence ... More
Index formulas and charge deficiencies on the Landau levelsMar 15 2010The notion of charge deficiency from Avron, Seiler, Simon (Charge deficiency, charge transport and comparison of dimensions, Comm. Math. Phys. 159) is studied from the view of $KK$-theory and is applied to the Landau levels in $\C^n$. We calculate the ... More
Rational Misiurewicz maps are rareJan 13 2007Mar 11 2007We show that the set of Misiurewicz maps has Lebesgue measure zero in the parameter space of rational maps for any fixed degree greater than or equal to 2.
On the differentiability conditions at spacelike infinityDec 12 1997We consider space-times which are asymptotically flat at spacelike infinity, i^0. It is well known that, in general, one cannot have a smooth differentiable structure at i^0, but have to use direction dependent structures. Instead of the oftenly used ... More
Rational Misiurewicz maps are rare IIMar 11 2007Feb 11 2008We show that the set of Misiurewicz maps has Lebesgue measure zero in the space of rational functions for any fixed degree greater than or equal to 2 (generalising the earlier version math.DS/0701382).
An invariant of link cobordisms from Khovanov homologyJun 28 2002Dec 23 2004In [Duke Math. J. 101 (1999) 359-426], Mikhail Khovanov constructed a homology theory for oriented links, whose graded Euler characteristic is the Jones polynomial. He also explained how every link cobordism between two links induces a homomorphism between ... More
A fast minimal solver for absolute camera pose with unknown focal length and radial distortion from four planar pointsMay 27 2018Jun 05 2018In this paper we present a fast minimal solver for absolute camera pose estimation from four known points that lie in a plane. We assume a perspective camera model with unknown focal length and unknown radial distortion. The radial distortion is modelled ... More
A new Eulerian model for viscous and heat conducting compressible flowJan 02 2018In this article, a suite of physically inconsistent properties of the Navier-Stokes equations, associated with the lack of mass diffusion and the definition of velocity, are presented. We show that these inconsistencies are consequences of the Lagrangian ... More
Shared matings in $V_2$Dec 22 2016Jan 09 2017We give a new constructive method to prove existence of shared matings in the special class $V_2$ consisting of rational maps with a super-attracting $2$-cycle (up to M\"obius conjugacy). The proof does not use Thurston's Theorem on branched coverings ... More
Statistical and knowledge supported visualization of multivariate dataAug 31 2010In the present work we have selected a collection of statistical and mathematical tools useful for the exploration of multivariate data and we present them in a form that is meant to be particularly accessible to a classically trained mathematician. We ... More
Operator-valued pseudo-differential operators and the twisted index pairingNov 26 2010Nov 10 2011The notion of pseudo-differential operators with coefficients in a continuous trace algebra over a manifold are introduced and their index theory is studied. The algebra of principal symbols in this calculus provides an abstract Poincar\'e dual to the ... More
Analytic formulas for topological degree of non-smooth mappings: the odd-dimensional caseApr 07 2010The notion of topological degree is studied for mappings from the boundary of a relatively compact strictly pseudo-convex domain in a Stein manifold into a manifold in terms of index theory of Toeplitz operators on the Hardy space. The index formalism ... More
The dual nest for degenerate Yoccoz puzzlesApr 08 2009The Yoccoz puzzle is a fundamental tool in Holomorphic Dynamics. The original combinatorial argument by Yoccoz, based on the Branner-Hubbard tableau, counts the preimages of a non-degenerate annulus in the puzzle. However, in some important new applications ... More
Equivariant extensions of *-algebrasMar 30 2010Nov 07 2010A bivariant functor is defined on a category of *-algebras and a category of operator ideals, both with actions of a second countable group $G$, into the category of abelian monoids. The element of the bivariant functor will be $G$-equivariant extensions ... More
Rational Misiurewicz maps for which the Julia set is not the whole sphereJun 26 2009We show that Misiurewicz maps for which the Julia set is not the whole sphere are Lebesgue density points of hyperbolic maps.
Static spacetimes with prescribed multipole moments; a proof of a conjecture by GerochJun 23 2009In this paper we give sufficient conditions on a sequence of multipole moments for a static spacetime to exist with precisely these moments. The proof is constructive in the sense that a metric having prescribed multipole moments up to a given order can ... More
Current-voltage relation for superconducting d-wave junctionsFeb 03 1997We calculate the current-voltage (I-V) relation for planar superconducting d-wave junctions for both arbitrary transmission of the junction and arbitrary orientation of the d-wave superconductors. The midgap states (MGS) present at interfaces/surfaces ... More
Hamiltonian Hopf bifurcations in the discrete nonlinear Schrödinger trimer: oscillatory instabilities, quasiperiodic solutions and a 'new' type of self-trapping transitionJul 30 2003Jan 08 2004Oscillatory instabilities in Hamiltonian anharmonic lattices are known to appear through Hamiltonian Hopf bifurcations of certain time-periodic solutions of multibreather type. Here, we analyze the basic mechanisms for this scenario by considering the ... More
Stochastic trapping in a solvable model of on-line independent component analysisMay 03 2001Previous analytical studies of on-line Independent Component Analysis (ICA) learning rules have focussed on asymptotic stability and efficiency. In practice the transient stages of learning will often be more significant in determining the success of ... More
AM to PM conversion of linear filtersMay 16 2018The conversion between amplitude modulation and phase modulation as a modulated signal goes thrugh a filter is analyzed. The difference in how the modulated sideband ampitude experience the filter, and how AM and PM has opposite signs for one of their ... More
The connection between polarization calculus and four-dimensional rotationsMar 07 2013We review the well-known polarization optics matrix methods, i.e., Jones and Stokes-Mueller calculus, and show how they can be formulated in terms of four-dimensional (4d) rotations of the four independent electromagnetic field quadratures. Since 4d rotations ... More
Abusing the Tutte Matrix: An Algebraic Instance Compression for the K-set-cycle ProblemJan 08 2013We give an algebraic, determinant-based algorithm for the K-Cycle problem, i.e., the problem of finding a cycle through a set of specified elements. Our approach gives a simple FPT algorithm for the problem, matching the $O^*(2^{|K|})$ running time of ... More
Bridgeland stability conditions on twisted Kummer surfacesJan 27 2012Sep 19 2012We construct a topological embedding of the maximal connected component of Bridgeland stability conditions of a (twisted) Abelian surface into the distinguished connected component of the stability manifold of the associated (twisted) Kummer surface. ... More
Algorithms for Grey-Weighted Distance ComputationsMay 08 2019With the increasing size of datasets and demand for real time response for interactive applications, improving runtime for algorithms with excessive computational requirements has become increasingly important. Many different algorithms combining efficient ... More
A Control-variable Regression Monte Carlo Technique for Short-term Electricity Generation PlanningDec 30 2015In the day-to-day operation of a power system, the system operator repeatedly solves short-term generation planning problems. When formulating these problems the operators have to weigh the risk of costly failures against increased production costs. The ... More
LP-branching algorithms based on biased graphsOct 19 2016We give a combinatorial condition for the existence of efficient, LP-based FPT algorithms for a broad class of graph-theoretical optimisation problems. Our condition is based on the notion of biased graphs known from matroid theory. Specifically, we show ... More
Semi-hyperbolic maps are rareMay 19 2016We prove in this paper that the set of semi-hyperbolic rational maps has Lebesgue measure zero in the space of rational maps of the Riemann sphere for a fixed degree d at least 2. It generalises an earlier result by J. Graczyk and the author who proved ... More
Maximal green sequences for preprojective algebrasApr 08 2015May 26 2015Maximal green sequences were introduced as combinatorical counterpart for Donaldson-Thomas invariants for 2-acyclic quivers with potential by B. Keller. We take the categorical notion and introduce maximal green sequences for hearts of bounded t-structures ... More
Phases of stable representations of quiversNov 27 2014We consider stable representations of non-Dynkin quivers with respect to a central charge. On one condition the existence of a stable representation with self-extensions implies the existence of infinitely many stables without self-extensions. In this ... More
A remark on twists and the notion of torsion-free discrete quantum groupsApr 01 2010Jan 31 2011In this paper twists of reduced locally compact quantum groups are studied. Twists of the dual coaction on a reduced crossed product are introduced and the twisted dual coactions are proved to satisfy a type of Takesaki-Takai duality. The twisted Takesaki-Takai ... More
Perturbations of rational Misiurewicz mapsApr 07 2008Jun 22 2009In this paper we investigate the perturbation properties of rational Misiurewicz maps, when the Julia set is the whole sphere (the other case is treated in [1]). In particular, we show that if f is a Misiurewicz map and not a flexible Lattes map, then ... More
Continuous-Variable Spatial Entanglement for Bright Optical BeamsJan 25 2005A light beam is said to be position squeezed if its position can be determined to an accuracy beyond the standard quantum limit. We identify the position and momentum observables for bright optical beams and show that position and momentum entanglement ... More
Intersubband Quantum Disc-in-Nanowire Photodetectors with Normal-incidence Response in the Long-wavelength InfraredSep 10 2017Semiconductor nanowires offer great potential for realizing broadband photodetectors that are compatible with silicon technology. However, the spectral range of such detectors has so far been limited to selected regions in the ultraviolet, visible and ... More
Optimum Small Optical Beam Displacement MeasurementJul 27 2004We derive the quantum noise limit for the optical beam displacement of a TEM00 mode. Using a multimodal analysis, we show that the conventional split detection scheme for measuring beam displacement is non-optimal with 80% efficiency. We propose a new ... More
Classification of plethories in characteristic zeroJan 05 2017We classify plethories over fields of characteristic zero, thus answering a question of Borger-Wieland and Bergman-Hausknecht. All plethories over characteristic zero fields are linear, in the sense that they are free plethories on a bialgebra. For the ... More
Construction of force measuring optical tweezers instrumentation and investigations of biophysical properties of bacterial adhesion organellesMar 03 2015Optical tweezers are a technique in which microscopic-sized particles, including living cells and bacteria, can be non-intrusively trapped with high accuracy solely using focused light. The technique has therefore become a powerful tool in the field of ... More
Modified Artificial Viscosity in Smooth Particle HydrodynamicsDec 05 1996Dec 12 1996Artificial viscosity is needed in Smooth Particle Hydrodynamics to prevent interparticle penetration, to allow shocks to form and to damp post shock oscillations. Artificial viscosity may, however, lead to problems such as unwanted heating and unphysical ... More
Decay of DNLS breathers through inelastic multiphonon scatteringDec 28 2000We consider the long-time evolution of weakly perturbed discrete nonlinear Schroedinger breathers. While breather growth can occur through nonlinear interaction with one single initial linear mode, breather decay is found to require excitation of at least ... More
New insights in brane and Kaluza--Klein theory through almost product structuresDec 18 1998We will show that gauge theory can be described by an almost product structure, which is a certain type of endomorphism of the tangent bundle. We will recover the gauge field strength as the Nijenhuis tensor of this endomorphism. We discuss a generalization ... More
The Use of Non-Spherical Kernels in Smooth Particle HydrodynamicsJun 07 1997A general expression for the momentum equation in the Smooth Particle Hydrodynacis approximation is derived for an arbitrary kernel, and compared with its spherical counterpart for various degrees of ellipsoidicity. For such an ellsipsoidal kernel the ... More
Initial-Boundary Value Problems for Parabolic EquationsSep 19 2008We prove new existence and uniqueness results for weak solutions to non-homogeneous initial-boundary value problems for parabolic equations modeled on the evolution of the p-Laplacian.
Diameter-dependent conductance of InAs nanowiresDec 22 2009Electrical conductance through InAs nanowires is relevant for electronic applications as well as for fundamental quantum experiments. Here we employ nominally undoped, slightly tapered InAs nanowires to study the diameter dependence of their conductance. ... More
From Motions to Emotions: Can the Fundamental Emotions be Expressed in a Robot Swarm?Mar 28 2019This paper explores the expressive capabilities of a swarm of miniature mobile robots within the context of inter-robot interactions and their mapping to the so-called fundamental emotions. In particular, we investigate how motion and shape descriptors ... More
Tree AutomataSep 21 2015This is a reissue of the book Tree Automata by F. G\'ecseg and M. Steinby originally published in 1984 by Akad\'emiai Kiad\'o, Budapest. Some mistakes have been corrected and a few obscure passages have been clarified. Moreover, some more recent contributions ... More
Growth and decay of discrete nonlinear Schroedinger breathers interacting with internal modes or standing-wave phononsFeb 11 2000We investigate the long-time evolution of weakly perturbed single-site breathers (localized stationary states) in the discrete nonlinear Schroedinger (DNLS) equation. The perturbations we consider correspond to time-periodic solutions of the linearized ... More
Realizing the analytic surgery group of Higson and Roe geometrically, Part III: Higher invariantsDec 04 2014Jan 08 2016We construct an isomorphism between the geometric model and Higson-Roe's analytic surgery group, reconciling the constructions in the previous papers in the series on "Realizing the analytic surgery group of Higson and Roe geometrically" with their analytic ... More
From Global Linear Computations to Local Interaction RulesNov 23 2013A network of locally interacting agents can be thought of as performing a distributed computation. But not all computations can be faithfully distributed. This paper investigates which global, linear transformations can be computed using local rules, ... More
Realizing the analytic surgery group of Higson and Roe geometrically, Part I: The geometric modelAug 27 2013Jan 27 2014We construct a geometric analog of the analytic surgery group of Higson and Roe for the assembly mapping for free actions of a group with values in a Banach algebra completion of the group algebra. We prove that the geometrically defined group, in analogy ... More
Tight Lower Bounds for the Workflow Satisfiability Problem Based on the Strong Exponential Time HypothesisAug 27 2015The Workflow Satisfiability Problem (WSP) asks whether there exists an assignment of authorized users to the steps in a workflow specification, subject to certain constraints on the assignment. The problem is NP-hard even when restricted to just not equals ... More
Spectral triples and finite summability on Cuntz-Krieger algebrasJan 09 2014Feb 27 2015We produce a variety of odd bounded Fredholm modules and odd spectral triples on Cuntz-Krieger algebras by means of realizing these algebras as "the algebra of functions on a non-commutative space" coming from a sub shift of finite type. We show that ... More
Control of cancellations that restrain the growth of a binomial recursionJun 07 2010We study a recursion that generates real sequences depending on a parameter $x$. Given a negative $x$ the growth of the sequence is very difficult to estimate due to canceling terms. We reduce the study of the recursion to a problem about a family of ... More
Entire functions with Julia sets of positive measureApr 08 2009Let f be a transcendental entire function for which the set of critical and asymptotic values is bounded. The Denjoy-Carleman-Ahlfors theorem implies that if the set of all z for which |f(z)|>R has N components for some R>0, then the order of f is at ... More
Elliptic Hypergeometric Solutions to Elliptic Difference EquationsMar 27 2009It is shown how to define difference equations on particular lattices $\{x_n\}$, $n\in\mathbb{Z}$, made of values of an elliptic function at a sequence of arguments in arithmetic progression (elliptic lattice). Solutions to special difference equations ... More
Ptolemaic IndexingNov 23 2009Jul 02 2015This paper discusses a new family of bounds for use in similarity search, related to those used in metric indexing, but based on Ptolemy's inequality, rather than the metric axioms. Ptolemy's inequality holds for the well-known Euclidean distance, but ... More
The group law on a tropical elliptic curveNov 22 2004In analogy with the classical group law on a plane cubic curve, we define a group law on a smooth plane tropical cubic curve. We show that the resulting group is isomorphic to $S^1$.
Monopole and Dyon Spectra in N=2 SYM with Higher Rank Gauge GroupsMar 20 1996Mar 25 1996We derive parts of the monopole and dyon spectra for N=2 super-Yang--Mills theories in four dimensions with gauge groups G of rank r>1 and matter multiplets. Special emphasis is put on G=SU(3) and those matter contents that yield perturbatively finite ... More
Tropical complete intersection curvesNov 13 2007A tropical complete intersection curve C in R^(n+1) is a transversal intersection of n smooth tropical hypersurfaces. We give a formula for the number of vertices of C given by the degrees of the tropical hypersurfaces. We also compute the genus of C ... More
Noether Supercurrents, Supergravity and Broken SupersymmetryNov 23 2018Nov 30 2018Some general aspects of supersymmetry and supergravity are briefly reviewed with emphasis on Noether supercurrents and their role in the discussion of supersymmetry breaking.
Reticulation-visible networksAug 21 2015Jun 25 2017Let $X$ be a finite set, $\mathcal N$ be a reticulation-visible network on $X$, and $\mathcal T$ be a rooted binary phylogenetic tree. We show that there is a polynomial-time algorithm for deciding whether or not $\mathcal N$ displays $\mathcal T$. Furthermore, ... More
Giant optical birefringence of semiconductor nanowire metamaterialsApr 26 2006Semiconductor nanowires exhibit large polarization anisotropy for the absorption and emission of light, making them ideal building blocks for novel photonic metamaterials. Here, we demonstrate that a high density of aligned nanowires exhibits giant optical ... More
Temperature dependence of an Efimov resonance in $^{39}\mathrm{K}$Jul 13 2018Nov 27 2018Ultracold atomic gases are an important testing ground for understanding few-body physics. In particular, these systems enable a detailed study of the Efimov effect. We use ultracold $^{39}\mathrm{K}$ to investigate the temperature dependence of an Efimov ... More
Quantum study of information delay in electromagetically induced transparencyJun 26 2006Using electromagnetically induced transparency (EIT), it is possible to delay and store light in atomic ensembles. Theoretical modelling and recent experiments have suggested that the EIT storage mechanism can be used as a memory for quantum information. ... More