Results for "Ian Walker"

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Even-integer continued fractions and the Farey treeAug 06 2015Singerman introduced to the theory of maps on surfaces an object that is a universal cover for any map. This object is a tessellation of the hyperbolic plane together with a certain subset of the ideal boundary. The 1-skeleton of this tessellation comprises ... More
Geodesic Rosen continued fractionsOct 06 2013Apr 21 2015We describe how to represent Rosen continued fractions by paths in a class of graphs that arise naturally in hyperbolic geometry. This representation gives insight into Rosen's original work about words in Hecke groups, and it also helps us to identify ... More
Bigraphical NetsFeb 26 2013Interaction nets are a graphical model of computation, which has been used to define efficient evaluators for functional calculi, and specifically lambda calculi with patterns. However, the flat structure of interaction nets forces pattern matching and ... More
An Energy Minimization Approach to 3D Non-Rigid Deformable Surface Estimation Using RGBD DataAug 02 2017We propose an algorithm that uses energy mini- mization to estimate the current configuration of a non-rigid object. Our approach utilizes an RGBD image to calculate corresponding SURF features, depth, and boundary informa- tion. We do not use predetermined ... More
An Expanded Chemo-dynamical Sample of Red Giants in the Bar of the Large Magellanic CloudApr 26 2017We report new spectroscopic observations obtained with the Michigan/Magellan Fiber System of 308 red giants (RGs) located in two fields near the photometric center of the bar of the Large Magellanic Cloud. This sample consists of 131 stars observed in ... More
Graph Convolutional Gaussian ProcessesMay 14 2019We propose a novel Bayesian nonparametric method to learn translation-invariant relationships on non-Euclidean domains. The resulting graph convolutional Gaussian processes can be applied to problems in machine learning for which the input observations ... More
Thermodynamics of a Simple Three-Dimensional DNA Hairpin ModelJun 23 2016We characterize the equation of state for a simple three-dimensional DNA hairpin model using a Metropolis Monte Carlo algorithm. This algorithm was run at constant temperature and fixed separation between the terminal ends of the strand. From the equation ... More
Semi-Supervised Learning via Compact Latent Space ClusteringJun 07 2018Jul 29 2018We present a novel cost function for semi-supervised learning of neural networks that encourages compact clustering of the latent space to facilitate separation. The key idea is to dynamically create a graph over embeddings of labeled and unlabeled samples ... More
Handling an uncertain control group event risk in non-inferiority trials: non-inferiority frontiers and the power-stabilising transformationMay 01 2019Background. Non-inferiority (NI) trials are increasingly used to evaluate new treatments expected to have secondary advantages over standard of care, but similar efficacy on the primary outcome. When designing a NI trial with a binary primary outcome, ... More
Detection of a population of carbon-enhanced metal-poor stars in the Sculptor dwarf spheroidal galaxyMar 12 2018Apr 25 2018The study of the chemical abundances of metal-poor stars in dwarf galaxies provides a venue to constrain paradigms of chemical enrichment and galaxy formation. Here we present metallicity and carbon abundance measurements of 100 stars in Sculptor from ... More
An update on the SCUBA-2 projectOct 19 2004SCUBA-2, which replaces SCUBA (the Submillimeter Common User Bolometer Array) on the James Clerk Maxwell Telescope (JCMT) in 2006, is a large-format bolometer array for submillimeter astronomy. Unlike previous detectors which have used discrete bolometers, ... More
Detailed Chemical Abundances in the r-Process-Rich Ultra-Faint Dwarf Galaxy Reticulum 2Jan 15 2016The ultra-faint dwarf galaxy Reticulum 2 (Ret 2) was recently discovered in images obtained by the Dark Energy Survey. We have observed the four brightest red giants in Ret 2 at high spectral resolution using the Michigan/Magellan Fiber System. We present ... More
Positive solutions of some parabolic system with cross-diffusion and nonlocal initial conditionsNov 15 2010The paper is concerned with a system consisting of two coupled nonlinear parabolic equations with a cross-diffusion term, where the solutions at positive times define the initial states. The equations arise as steady state equations of an age-structured ... More
Universal properties of bicategories of polynomialsJun 27 2018Dec 23 2018We establish the universal properties of the bicategory of polynomials, considering both cartesian and general morphisms between these polynomials. A direct proof of these universal properties would be impractical due to the complicated coherence conditions ... More
Yoneda structures and KZ doctrinesMar 25 2017Aug 09 2017In this paper we strengthen the relationship between Yoneda structures and KZ doctrines by showing that for any locally fully faithful KZ doctrine, with the notion of admissibility as defined by Bunge and Funk, all of the Yoneda structure axioms apart ... More
Positive Equilibrium Solutions for Age and Spatially Structured Population ModelsFeb 17 2009The existence of positive equilibrium solutions to age-dependent population equations with nonlinear diffusion is studied in an abstract setting. By introducing a bifurcation parameter measuring the intensity of the fertility it is shown that a branch ... More
D1-D5-P superstrata in 5 and 6 dimensions: separable wave equations and prepotentialsJun 10 2019We construct the most general single-mode superstrata in 5 dimensions with ambipolar, two centered Gibbons Hawking bases, via dimensional reduction of superstrata in 6 dimensions. Previously, asymptotically $\text{AdS}_{3}\times \mathbb{S}^{2}$ 5-dimensional ... More
Stable commutator length in free products of cyclic groupsApr 23 2013We give an algorithm to compute stable commutator length in free products of cyclic groups which is polynomial time in the length of the input, the number of factors, and the orders of the finite factors. We also describe some experimental and theoretical ... More
Coefficient growth in square chainsFeb 27 2019Suppose $((\cdots((x^{2}-c_{1})^{2}-c_{2})^{2}\cdots)^{2}-c_{k-1})^{2}-c_{k}$ splits into linear factors over $\mathbb{Z}$ and $c_{k}\neq0$. We show that for each $j$ and each prime $p$, if $p\leq2^{j-1}$ then $p$ divides $c_{j}$. Consequently, $$\ln ... More
A Categorification of Hall AlgebrasMar 31 2013Apr 02 2013In recent years, there has been great interest in the study of categorification, specifically as it applies to the theory of quantum groups. In this thesis, we would like to provide a new approach to this problem by looking at Hall algebras. It is know, ... More
Global Continua of Positive Equilibria for some Quasilinear Parabolic Equation with a Nonlocal Initial ConditionJul 09 2012This paper is concerned with a quaslinear parabolic equation including a nonlinear nonlocal initial condition. The problem arises as equilibrium equation in population dynamics with nonlinear diffusion. We make use of global bifurcation theory to prove ... More
Coexistence Steady States in a Predator-Prey ModelFeb 09 2010An age-structured predator-prey system with diffusion and Holling-Tanner-type nonlinearities is considered. Regarding the intensity of the fertility of the predator as bifurcation parameter, we prove that a branch of positive coexistence steady states ... More
Age-dependent equations with non-linear diffusionOct 30 2008We consider the well-posedness of models involving age structure and non-linear diffusion. Such problems arise in the study of population dynamics. It is shown how diffusion and age boundary conditions can be treated that depend non-linearly and possibly ... More
Stable immersions in orbifoldsDec 10 2013Aug 21 2014We prove that in any hyperbolic orbifold with one boundary component, the product of any hyperbolic fundamental group element with a sufficiently large multiple of the boundary is represented by a geodesic loop that virtually bounds an immersed surface. ... More
Quantifying the Fragility of Galactic Disks in Minor MergersOct 09 1995We perform fully self-consistent stellar dynamical simulations of the accretion of a companion ("satellite") galaxy by a large disk galaxy to investigate the interaction between the disk, halo, and satellite components of the system during a merger. Our ... More
Dynamic Control of Pneumatic Muscle ActuatorsNov 12 2018Pneumatic muscle actuators (PMA) are easy-to-fabricate, lightweight, compliant, and have high power-to-weight ratio, thus making them the ideal actuation choice for many soft and continuum robots. But so far, limited work has been carried out in dynamic ... More
Center of Gravity-based Approach for Modeling Dynamics of Multisection Continuum ArmsJan 06 2019Multisection continuum arms offer complementary characteristics to those of traditional rigid-bodied robots. Inspired by biological appendages, such as elephant trunks and octopus arms, these robots trade rigidity for compliance, accuracy for safety, ... More
Revisiting 154-day periodicity in the occurrence of hard flares. A planetary influence?Nov 14 2016Rieger et al (1984) reported observations of a 154 day periodicity in flares during solar cycle 21. This paper discusses the observations in the light of a simple empirical planetary model of sunspot emergence. The planetary model predicts sunspot emergence ... More
Lower bounds on volumes of hyperbolic Haken 3-manifoldsJun 27 1999In this paper, we find lower bounds for volumes of hyperbolic 3-manifolds with various topological conditions. Let V_3 = 1.01494 denote the volume of a regular ideal simplex in hyperbolic 3-space. As a special case of the main theorem, if a hyperbolic ... More
The closed string tadpole in open string field theoryApr 07 2008We compute a class of gauge invariant observables for marginal solutions and the tachyon vacuum. In each case we find that the observables are related in a simple way to the closed-string tadpole on a disk with appropriate boundary conditions. We give ... More
Generalized five-dimensional Kepler system, Yang-Coulomb monopole and Hurwitz transformationSep 21 2011Mar 25 2012The 5D Kepler system possesses many interesting properties. This system is superintegrable and also with a $su(2)$ nonAbelian monopole interaction (Yang-Coulomb monopole). This system is also related to a 8D isotropic harmonic oscillator by a Hurwitz ... More
Polynomial Associative Algebras for Quantum Superintegrable Systems with a Third Order Integral of MotionJan 26 2007We consider a superintegrable Hamiltonian system in a two-dimensional space with a scalar potential that allows one quadratic and one cubic integral of motion. We construct the most general associative cubic algebra and we present specific realizations. ... More
Quartic Poisson algebras and quartic associative algebras and realizations as deformed oscillator algebrasApr 26 2013We introduce the most general quartic Poisson algebra generated by a second and a fourth order integral of motion of a 2D superintegrable classical system. We obtain the corresponding quartic (associative) algebra for the quantum analog and we extend ... More
Cosmological and Astrophysical Constraints on Tensor UnparticlesOct 23 2007We calculate cosmological and astrophysical bounds on the couplings between standard model fields and tensor unparticles. The present day density of tensor unparticles from neutrino-neutrino and photon-photon annihilation is calculated. Also, the supernovae ... More
Sandwich Structures from Arbitrary Functions in Group TheoryDec 07 2017Functions between groups with the property that all function con- jugates are inverse preserving are called sandwich morphisms. These maps pre- serve a structure within the group known as the sandwich structure. Sandwich structures are left distributive ... More
Some Examples of Free actions on Products of SpheresSep 08 2003Jan 26 2006If $G_1$ and $G_2$ are finite groups with periodic Tate cohomology, then $G_1\times G_2$ acts freely and smoothly on some product $S^n \times S^n$.
Superintegrability and higher order polynomial algebras IAug 30 2009We present a method to obtain higher order integrals and polynomial algebras for two-dimensional superintegrable systems from creation and annihilation operators. All potentials with a second and a third order integrals of motion separable in Cartesian ... More
Finding a Zipf distribution and cascading propagation metric in utility line outage dataAug 25 2018Observed transmission line outage data is grouped into successive generations of events. The empirical distribution of the number of generations in the cascades follows a Zipf distribution that implies the increasing propagation as cascades progress. ... More
The Convolution AlgebraFeb 09 2017For a complete lattice $L$ and a relational structure $\mathfrak{X}=(X,(R_i)_I)$, we introduce the convolution algebra $L^{\mathfrak{X}}$. This algebra consists of the lattice $L^X$ equipped with an additional $n_i$-ary operation $f_i$ for each $n_i+1$-ary ... More
Evidence of two different types of short term solar modulation of regional surface temperature and cloudJan 22 2014Recent work indicates that 27 day variations in cosmic ray flux during 2007 2009 are phase locked to 27 day variations in cloud and surface temperature at Shetland. Here we extend the study to other regions including Central England, US and Australia ... More
Cross-Polarized Microwave Surface-State Anti-ResonanceOct 22 2013Jul 14 2014We propose a polarization-sensitive measurement of microwave electromagnetic resonances in a magnetic field to detect the metallic surface state of a bulk insulator. A quantitative model is used to demonstrate that a unique, unambiguous signature of the ... More
Introduction to Spin-Polarized Ballistic Hot Electron Injection and Detection in SiliconOct 14 2009Ballistic hot electron transport overcomes the well-known problems of conductivity and spin lifetime mismatch that plagues spin injection in semiconductors with ferromagnetic ohmic contacts. Through the spin-dependent mean-free-path, it also provides ... More
Human-Machine Symbiosis, 50 Years OnDec 13 2007Licklider advocated in 1960 the construction of computers capable of working symbiotically with humans to address problems not easily addressed by humans working alone. Since that time, many of the advances that he envisioned have been achieved, yet the ... More
Special Lagrangian cones in C^3 and primitive harmonic mapsJan 17 2002Jul 02 2002In this article I show that every special Lagrangian cone in C^3 determines, and is determined by, a primitive harmonic surface in the 6-symmetric space SU_3/SO_2. For cones over tori, this allows us to use the classification theory of harmonic tori to ... More
Factorization and high-energy effective actionDec 10 1998I demonstrate that the amplitude for high-energy scattering can be factorized as a convolution of the contributions due to fast and slow fields. The fast and slow fields interact by means of Wilson-line operators -- infinite gauge factors ordered along ... More
Mellin representation of the graviton bulk-to-bulk propagator in AdSFeb 02 2011A Mellin-type representation of the graviton bulk-to-bulk propagator from Ref. 1 in terms of the integral over the product of bulk-to-boundary propagators is derived.
Effective field theory for the small-x evolutionMay 31 2001The small-x behavior of structure functions in the saturation region is determined by the non-linear generalization of the BFKL equation. I suggest the effective field theory for the small-x evolution which solves formally this equation. The result is ... More
Operator Expansion for Diffractive High-Energy ScatteringJun 18 1997I discuss the operator expansion for diffractive high-energy scattering and present the non-linear evolution equation for the relevant Wilson-line operators which describes both the propagator of the BFKL pomeron and the three-pomeron vertex.
T Parity and the Littlest HiggsSep 02 2004Sep 10 2004We construct T-parity invariant extensions of the littlest Higgs model, in which only linear representations of the full symmetry group are employed, without recourse to the non-linear representations introduced by Coleman, Callan, Wess, and Zumino (CCWZ). ... More
Model Independent Extractions of |V_{ub}| from Inclusive B DecaysSep 15 2000We discuss the possibility of extracting |V_{ub}| from various spectra of inclusive B decays, without large systematic errors which usually arise from having to model the Fermi motion of the heavy quark. This strategy can be applied to the electron energy ... More
Polarized Charginos (and Tops) in Stop DecaysApr 01 2013Mar 31 2014Current searches for direct production of scalar top quarks, or stops, in supersymmetry focus on their decays into W boson + b quark + neutralino by way of top + neutralino and bottom + chargino. While the polarization of the top quark depends on the ... More
Soliton Confinement and the Excitation Spectrum of Spin-Peierls AntiferromagnetsMay 14 1997The excitation spectrum of spin-Peierls antiferromagnets is discussed taking into acount phonon dynamics but treating inter-chain elastic couplings in mean field theory. This gives a ladder of soliton -anti-soliton boundstates, with no soliton continuum, ... More
Classical ladder operators, polynomial Poisson algebras and classification of superintegrable systemsSep 21 2011Mar 19 2012We recall results concerning one-dimensional classical and quantum systems with ladder operators. We obtain the most general one-dimensional classical systems respectively with a third and a fourth order ladder operators satisfying polynomial Heisenberg ... More
An infinite family of superintegrable systems from higher order ladder operators and supersymmetryAug 18 2010Dec 23 2010We will discuss how we can obtain new quantum superintegrable Hamiltonians allowing the separation of variables in Cartesian coordinates with higher order integrals of motion from ladder operators. We will discuss also how higher order supersymmetric ... More
Decay of correlations for slowly mixing flowsNov 06 2006We show that polynomial decay of correlations is prevalent for a class of nonuniformly hyperbolic flows. These flows are the continuous time analogue of a class of nonuniformly hyperbolic diffeomorphisms for which Young proved polynomial decay of correlations. ... More
Superintegrability with third order integrals of motion, cubic algebras and supersymmetric quantum mechanics II:Painleve transcendent potentialsNov 10 2008Apr 20 2009We consider a superintegrable quantum potential in two-dimensional Euclidean space with a second and a third order integral of motion. The potential is written in terms of the fourth Painleve transcendent. We construct for this system a cubic algebra ... More
MIMO Z Channel Interference ManagementMar 31 2012MIMO Z Channel is investigated in this paper. We focus on how to tackle the interference when different users try to send their codewords to their corresponding receivers while only one user will cause interference to the other. We assume there are two ... More
Gradient Masking Causes CLEVER to Overestimate Adversarial Perturbation SizeApr 21 2018A key problem in research on adversarial examples is that vulnerability to adversarial examples is usually measured by running attack algorithms. Because the attack algorithms are not optimal, the attack algorithms are prone to overestimating the size ... More
Curvature-driven wrinkling of thin elastic shellsJun 05 2019Jun 09 2019How much energy does it take to stamp a thin elastic shell flat? Motivated by recent experiments on the wrinkling patterns formed by thin shells floating on a water bath, we develop a rigorous method via $\Gamma$-convergence for answering this question ... More
A Condition Number for Hamiltonian Monte CarloMay 23 2019Jun 03 2019Hamiltonian Monte Carlo is a popular sampling technique for smooth target densities. The scale lengths of the target have long been believed to influence sampling efficiency, but quantitative measures intrinsic to the target have been lacking. In this ... More
New CleverHans Feature: Better Adversarial Robustness Evaluations with Attack BundlingNov 08 2018This technical report describes a new feature of the CleverHans library called "attack bundling". Many papers about adversarial examples present lists of error rates corresponding to different attack algorithms. A common approach is to take the maximum ... More
A Distributed Reinforcement Learning Solution With Knowledge Transfer Capability for A Bike Rebalancing ProblemOct 09 2018Rebalancing is a critical service bottleneck for many transportation services, such as Citi Bike. Citi Bike relies on manual orchestrations of rebalancing bikes between dispatchers and field agents. Motivated by such problem and the lack of smart autonomous ... More
Piecewise linear homeomorphisms of the real lineMar 17 2007Brin and Squier described how to classify the elements of the group of piecewise linear homeomorphisms of the real line according to conjugacy. We supply a short account of the key step in their classification. The results in this document are unoriginal. ... More
Link cobordisms and absolute gradings on link Floer homologyJan 12 2017Oct 18 2018We show that the link cobordism maps defined by the author are graded and satisfy a grading change formula. Using the grading change formula, we prove a new bound for $\Upsilon_K(t)$ for knot cobordisms in negative definite 4-manifolds. As another application, ... More
Graph cobordisms and Heegaard Floer homologyDec 03 2015May 10 2019We construct a graph TQFT for the minus flavor of Heegaard Floer homology. Our graph TQFT extends Ozsv\'{a}th and Szab\'{o}'s TQFT for closed and connected 3-manifolds, and allows for cobordisms with disconnected ends. As an application, we give an explicit ... More
Tangency bifurcation of invariant manifolds in a slow-fast systemDec 15 2015We study a three-dimensional dynamical system in two slow variables and one fast variable. We analyze the tangency of the unstable manifold of an equilibrium point with "the" repelling slow manifold, in the presence of a stable periodic orbit emerging ... More
Two remarks on Wall's D2 problemAug 28 2017If a finite group $G$ is isomorphic to a subgroup of $SO(3)$, then $G$ has the D2-property. Let $X$ be a finite complex satisfying Wall's D2-conditions. If $\pi_1(X)=G$ is finite, and $\chi(X) \geq 1-Def(G)$, then $X \vee S^2$ is simple homotopy equivalent ... More
A Perfect Set of Reals with Finite Self-InformationOct 29 2012We examine a definition of the mutual information of two reals proposed by Levin. The mutual information is I(X:Y)=log(sum(2^{K(s)-K^X(s)+K(t)-K^Y(t)-K(s,t)}, (s,t) pairs of finite binary strings), where K is the prefix-free Kolmogorov complexity. A real ... More
Ford circles, continued fractions, and best approximation of the second kindDec 10 2009We give an elementary geometric proof using Ford circles that the convergents of the continued fraction expansion of a real number $\alpha$ coincide with the rationals that are best approximations of the second kind of $\alpha$.
Generalized Weyl algebras: category O and graded Morita equivalenceApr 23 2009Nov 04 2009We study the structural and homological properties of graded Artinian modules over generalized Weyl algebras (GWAs), and this leads to a decomposition result for the category of graded Artinian modules. Then we define and examine a category of graded ... More
On representation schemes and Grassmanians of finite dimensional algebras and a construction of LusztigNov 10 2009Sep 01 2010Let I be a finite set and CI be the algebra of functions on I. For a finite dimensional C algebra A with \CI contained in A we show that certain moduli spaces of finite dimsional modules are isomorphic to certain Grassmannian (quot-type) varieties. There ... More
Classifying SL$_2$-tilingsApr 26 2019Recently much research has gone into classifying $\text{SL}_2$-tilings. Generally, combinatorial methods are used, involving triangulations of regions and inventive counting techniques. Here we give a unified approach to such classifications by using ... More
Asymptotic stability of shear-flow solutions to incompressible viscous free boundary problems with and without surface tensionAug 07 2017This paper concerns the dynamics of a layer of incompressible viscous fluid lying above a rigid plane and with an upper boundary given by a free surface. The fluid is subject to a constant external force with a horizontal component, which arises in modeling ... More
The role of mutation rate variation and genetic diversity in the architecture of human diseaseAug 29 2013We have investigated the role that the mutation rate and the structure of genetic variation at a locus play in determining whether a gene is involved in disease. We predict that the mutation rate and its genetic diversity should be higher in genes associated ... More
Use of Taus in ATLASOct 24 2002At the LHC, new particles can be expected that decay to final states involving taus. Examples are given from simulations by the ATLAS experiment showing how such final states can be exploited.
Factorization for high-energy scatteringJul 21 1998I demonstrate that the amplitude of the high-energy scattering can be factorized in a product of two independent functional integrals over "fast" and "slow" fields which interact by means of Wilson-line operators -- gauge factors ordered along the straight ... More
Ginzburg-Landau vortex dynamics driven by an applied boundary currentJul 06 2009Mar 24 2010In this paper we study the time-dependent Ginzburg-Landau equations on a smooth, bounded domain $\Omega \subset \Rn{2}$, subject to an electrical current applied on the boundary. The dynamics with an applied current are non-dissipative, but via the identification ... More
Pants immersed in hyperbolic 3-manifoldsFeb 19 2008We show that an immersed thrice-punctured sphere in a cusped orientable hyperbolic 3-manifold is either embedded or has a single clasp in a manifold obtained by hyperbolic Dehn filling on a cusp of the Whitehead link complement.
Near-Infrared Imaging of a Group or Cluster of Galaxies at a Redshift of 2.39Jan 15 1998At z=2.39, the cluster around 53W002 is one of the most distant groups or clusters of galaxies known to date. At this redshift the 4000A-break falls between the J and H bands, thus our infrared observations are designed to identify cluster members by ... More
The Social Architecture of CapitalismJan 06 2004Mar 23 2011A dynamic model of the social relations between workers and capitalists is introduced. The model is deduced from the assumption that the law of value is an organising principle of modern economies. The model self-organises into a dynamic equilibrium with ... More
The duration of recessions follows an exponential not a power lawNov 25 2003Mar 23 2011Ormerod and Mounfield analysed GDP data of 17 leading capitalist economies from 1870 to 1994 and concluded that the frequency of the duration of recessions is consistent with a power-law. But in fact the data is consistent with an exponential (Boltzmann-Gibbs) ... More
The Kondo screening cloud: what it is and how to observe itNov 11 2009Jan 08 2010The Kondo effect involves the formation of a spin singlet by a magnetic impurity and conduction electrons. It is characterized by a low temperature scale, the Kondo temperature, $T_K$, and an associated long length scale, $\xi_K = \hbar v_F/(k_BT_K)$ ... More
Edge Magnetic Field in the xxz Spin-1/2 ChainOct 21 1997Feb 12 1998The critical behavior associated with a transverse magnetic field applied at the edge of a semi-infinite xxz S=1/2 chain is calculated using field theory techniques. Contrary to a recent claim, we find that the long-time behavior is given by a renormalization ... More
Boundary Condition Changing Operators in Conformal Field Theory and Condensed Matter PhysicsNov 09 1996Boundary condition changing operators in conformal field theory describe various types of "sudden switching" problems in condensed matter physics such as the X-ray edge singularity. We review this subject and give two extensions of previous work. A general ... More
Generalized MICZ-Kepler system, duality, polynomial and deformed oscillator algebrasApr 26 2010Aug 27 2010We present the quadratic algebra of the generalized MICZ-Kepler system in three-dimensional Euclidean space $E_{3}$ and its dual the four dimensional singular oscillator in four-dimensional Euclidean space $E_{4}$. We present their realization in terms ... More
Generalized Kaluza-Klein monopole, quadratic algebras and ladder operatorsMar 02 2011We present a generalized Kaluza-Klein monopole system. We solve this quantum superintegrable systems on a Euclidean Taub Nut manifold using the separation of variables of the corresponding Schroedinger equation in spherical and parabolic coordinates. ... More
Planetary model of sunspot emergence: A spectral and autocorrelation analysisOct 09 2016This paper is concerned with intermediate range periodicity in the sunspot area spectrum. An empirical model of sunspot area emergence based on Mercury planet conjunctions was developed and the spectra of the model variation and the sunspot area variation ... More
Tunnel conductance spectroscopy via harmonic generation in a hybrid capacitor deviceMar 19 2013Jul 30 2013We address the measurement of density of states within and beyond the superconducting gap in tunnel-coupled finite-size nanostructures using a capacitive method. Third-harmonic generation is used to yield the full differential conductance spectrum without ... More
Summary talk: Gauge Boson Self InteractionsApr 03 1995A review is given of the theoretical expectations of the self couplings of gauge bosons and of the present experimental information on the couplings. The possibilities for future measurements are also discussed.
On the semi-annual, 27 day, variation in geomagnetic activity, cloud cover and surface temperatureDec 03 2013We develop a basic model of the time variation of geomagnetic activity and show that the model predicts, with decreasing levels of exactitude, the time variation of the ~27 day period components of geomagnetic aa index, cloud cover and surface temperature ... More
The evolvability of business and the role of antitrustMar 06 2012In this paper, based on theories of complex adaptive systems, I argue that the main case for antitrust policy should be extended to include the criteria of "evolvability." To date, the main case focuses on economizing, including market power as a key ... More
Multiple Dirichlet Series for Affine Weyl GroupsJun 03 2014Let $W$ be the Weyl group of a simply-laced affine Kac-Moody Lie group, excepting $\tilde{A}_n$ for $n$ even. We construct a multiple Dirichlet series $Z(x_1, \ldots x_{n+1})$, meromorphic in a half-space, satisfying a group $W$ of functional equations. ... More
Ideal Triangulations of Pseudo-Anosov Mapping ToriAug 09 2010Aug 21 2010We show how to construct an ideal triangulation of a mapping torus of a pseudo-Anosov map punctured along the singular fibers. This gives rise to a new conjugacy invariant of mapping classes, and a new proof of a theorem of Farb-Leininger-Margalit. The ... More
Tameness of hyperbolic 3-manifoldsMay 29 2004We show that hyperbolic 3-manifolds with finitely generated fundamental group are tame, that is the ends are products. We actually work in slightly greater generality with pinched negatively curved manifolds with hyperbolic cusps. This answers a conjecture ... More
AGN astrophysics from comparing radio and Gaia optical astrometryJan 29 2013Gaia will open up a huge volume of new parameter space in which to explore the physics of AGN and black hole evolution. We address the question as to how far along the relativistic jets blazar radio, optical and gamma ray emission originated. In some ... More
A conjecture on the distribution of firm profitJul 27 2004Mar 23 2011A common assumption of political economy is that profit rates across firms or sectors tend to uniformity, and often models are formulated in which this tendency is assumed to have been realised. But in reality this tendency is never realised and the distribution ... More
Exact Correlation Amplitude for the S=1/2 Heisenberg Antiferromagnetic ChainFeb 04 1998Feb 20 1998The exact amplitude for the asymptotic correlation function in the S=1/2 Heisenberg antiferromagnetic chain is determined: <S^a_0 S^b_r> goes to (-1)^r delta^{ab}(ln r)^{1/2}/[(2 pi)^{3/2}r]. The behaviour of the correlation functions for small xxz anisotropy ... More
Non-Fermi liquid behavior in Kondo modelsSep 07 2004Despite the fact that the low energy behavior of the basic Kondo model cannot be studied perturbatively it was eventually shown by Wilson, Anderson, Nozieres and others to have a simple "local Fermi liquid theory" description. That is, electronic degrees ... More
The Kondo Screening CloudNov 17 2001Renormalization group theory of the Kondo effect predicts that an impurity spin is screened by a conduction electron spread over a large distance of order >.1 to 1 micron. This review has the following sections: 1. The Kondo effect and the screening cloud, ... More
Evidence of a planetary influence on solar activity: Phase coherence of the variation in sunspot area with the tidal effect of MercuryOct 08 2015There have been numerous reports of quasiperiodicities in solar activity in the intermediate period range. However, no accepted explanation for the episodic occurrence of quasiperiodicities has emerged. This paper examines the possibility that the periodicities ... More