Results for "Paul Hickson"

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Wide-field tracking with zenth-pointing telescopesJun 12 2001Equipped with a suitable optical relay system, telescopes employing low-cost fixed primary mirrors could point and track while delivering high-quality images to a fixed location. Such an optical tracking system would enable liquid-mirror telescopes to ... More
Eliminating the Coriols Effect in Liquid MirrorsAug 18 2001If uncorrected, the Coriolis force due to the rotation of the Earth causes significant aberration of images produced by large liquid-mirror telescopes. We show that this problem can be eliminated by a fixed compensating tilt of the liquid-mirror rotation ... More
A Technique for Photometric Detection and Measurement of Unresolved Binary SystemsNov 29 1997A technique is described for the detection and measurement of close binary systems whose images are unresolved. The method is based on analysis of the moment of inertia tensor of the image, from which the product of the binary flux ratio and square of ... More
Compact groups of galaxiesOct 25 1997Compact groups of galaxies have posed a number of challenging questions. Intensive observational and theoretical studies are now providing answers to many of these, and at the same time, are revealing unexpected new clues about the nature and role of ... More
UBC-NASA Multi-Narrowband Survey. I. Description and Photometric Properties of the SurveyOct 03 1997Observations, analysis techniques and photometric properties of a multi-narrowband survey of a 20 square-degree area of sky at +33 degrees declination are described. The survey is conducted with the 3-meter liquid-mirror telescope of the NASA Orbital ... More
A Curvature-Compensated Corrector for Drift-Scan ObservationsJun 23 1998Images obtained by drift-scanning with a stationary telescope are affected by the declination-dependent curvature of star trails. The image displacement to curvature and drift rate variation increases with the angular field of view and can lead to significant ... More
Topology of the Las Campanas Redshift SurveyJul 10 2000Jul 12 2000The topology of the Las Campanas Redshift Survey is analyzed using Minkowski functional statistics, taking into account the selection effects of the survey. The results are compared with the predictions of some toy models of structure formation, including ... More
The Large Zenith Telescope Survey: a deep survey using a 6-m liquid mirror telescopeDec 18 2001The Large Zenith Telescope Survey whose construction is almost completed (first light expected in spring 2002) near Vancouver (Canada) is designed to observed a total strip of ~17' x 120 deg in 40 medium-band filters spanning 4000-10000 A. It will gather ... More
The 2-point angular correlation function of 20,000 galaxies to V<23.5 and I<22Jul 13 2000The UH8K wide field camera of the CFHT was used to image 0.68 deg^2 of sky. From these images, ~20,000 galaxies were detected to completeness magnitudes V<23.5 and I<22.5. The angular correlation function of these galaxies is well represented by the parameterization ... More
Classification and redshift estimation by principal component analysisJun 04 2002Jun 07 2002We show that the first 10 eigencomponents of the Karhunen-Lo\`eve expansion or Principal Component Analysis (PCA) provide a robust classification scheme for the identification of stars, galaxies and quasi-stellar objects from multi-band photometry. To ... More
Polarization-driven spin precession of mesospheric sodium atomsSep 11 2018We report experimental results on the first on-sky observation of atomic spin precession of mesospheric sodium driven by polarization modulation of a continuous-wave laser. The magnetic resonance was remotely detected from the ground by observing the ... More
Remote sensing of geomagnetic fields and atomic collisions in the mesosphereFeb 09 2018Magnetic-field sensing has contributed to the formulation of the plate-tectonics theory, the discovery and mapping of underground structures on Earth, and the study of magnetism in other planets. Filling the gap between space-based and near-Earth observation, ... More
The fast C(3P) + CH3OH reaction as an efficient loss process for gas-phase interstellar methanolJun 05 2014Rate constants for the C(3P) + CH3OH reaction have been measured in a continuous supersonic flow reactor over the range 50 K to 296 K. C(3P) was created by the in-situ pulsed laser photolysis of CBr4, a multiphoton process which also produced some C(1D), ... More
Discordant Redshifts in Compact GroupsOct 17 1996This paper addresses the long standing question of discordant redshifts in compact groups. We have used an homogenous catalogue of 173 compact groups selected by an automated procedure to objectively predict the fraction of discordant redshifts with high ... More
Detection of CH3SH in protostar IRAS 16293-2422Feb 24 2016The nature of the main sulphur reservoir in star forming regions is a long standing mystery. The observed abundance of sulphur-bearing species in dense clouds is only about 0.1 per cent of the same quantity in diffuse clouds. Therefore, the main sulphur ... More
Using Site Testing Data for Adaptive Optics SimulationsJan 12 2011Astronomical Site testing data plays a vital role in the simulation, design, evaluation and operation of adaptive optics systems for large telescope. We present the example of TMT and its first light facilitiy adaptive optics system NFIRAOS, and illustrate ... More
A cryogenic liquid-mirror telescope on the moon to study the early universeJun 13 2008We have studied the feasibility and scientific potential of zenith observing liquid mirror telescopes having 20 to 100 m diameters located on the moon. They would carry out deep infrared surveys to study the distant universe and follow up discoveries ... More
An experimental and theoretical investigation of the C(1D) + D2 reactionNov 06 2016In a previous joint experimental and theoretical study of the barrierless chemical reaction C(1D) + H2 at low temperatures (300-50 K) [K. M. Hickson, J.-C. Loison, H. Guo, Y. V. Suleimanov, J. Phys. Chem. Lett., 2015, 6, 4194.], excellent agreement was ... More
Unusual Low Temperature Reactivity of Water. The CH + H2O Reaction as a Source of Interstellar Formaldehyde?Aug 19 2013Water is an important reservoir species for oxygen in interstellar space and plays a key role in the physics of star formation through cooling by far-infrared emission. Whilst water vapour is present at high abundances in the outflows of protostars, its ... More
Semantic Instance Labeling Leveraging Hierarchical SegmentationAug 02 2017Most of the approaches for indoor RGBD semantic la- beling focus on using pixels or superpixels to train a classi- fier. In this paper, we implement a higher level segmentation using a hierarchy of superpixels to obtain a better segmen- tation for training ... More
Similarity-based Browsing over Linked Open DataJun 21 2011An increasing amount of data is published on the Web according to the Linked Open Data (LOD) principles. End users would like to browse these data in a flexible manner. In this paper we focus on similarity-based browsing and we introduce a novel method ... More
Topological Statistics and the LMT Galaxy Redshift SurveyJun 26 1998The results of numerical simulations are presented which demonstrate that liquid mirror telescope galaxy redshift surveys such as the current UBC-NASA Multi-Narrowband Survey and the future LZT Survey have the potential of discriminating between the predictions ... More
The dynamics of domain wall SkyrmionsMay 13 2013It has recently been shown that Skyrmions with a fixed size can exist in theories without a Skyrme term, providing the Skyrmion is located on a domain wall. Here we numerically compute domain wall Skyrmions of this type, in a (2+1)-dimensional O(3) sigma ... More
Automorphisms of $\mathscr{P}(λ)/\mathscr{I}_κ$Jun 10 2015Aug 27 2015We study conditions on automorphisms of Boolean algebras of the form $P(\lambda)/I_\kappa$ (where $\lambda$ is an uncountable cardinal and $I_\kappa$ is the ideal of sets of cardinality less than $\kappa$) which allow one to conclude that a given automorphism ... More
A proposed chemical scheme for HCCO formation in cold dense cloudsSep 01 2015The ketenyl radical (HCCO) has recently been discovered in two cold dense clouds with a non-negligible abundance of a few 1e-11 (compared to H2) (Agundez et al. 2015). Until now, no chemical network has been able to reproduce this observation. We propose ... More
Methylacetylene (CH3CCH) and propene (C3H6) formation in cold dense clouds: a case of dust grain chemistryMar 08 2016We present an extensive review of gas phase reactions producing methylacetylene and propene showing that these relatively abundant unsaturated hydrocarbons cannot be synthesized through gas-phase reactions. We explain the formation of propene and methylacetylene ... More
Isotopic fractionation of carbon, deuterium and nitrogen : a full chemical studyJan 06 2015Jan 08 2015Context. The increased sensitivity and high spectral resolution of millimeter telescopes allow the detection of an increasing number of isotopically substituted molecules in the interstellar medium. The 14N/ 15N ratio is difficult to measure directly ... More
Efficient Hierarchical Graph-Based Segmentation of RGBD VideosJan 26 2018We present an efficient and scalable algorithm for segmenting 3D RGBD point clouds by combining depth, color, and temporal information using a multistage, hierarchical graph-based approach. Our algorithm processes a moving window over several point clouds ... More
Astronomical seeing and ground-layer turbulence in the Canadian High ArcticMay 03 2013We report results of a two-year campaign of measurements, during arctic winter darkness, of optical turbulence in the atmospheric boundary-layer above the Polar Environment Atmospheric Laboratory in northern Ellesmere Island (latitude +80 deg N). The ... More
Temporal variability of the telluric sodium layerSep 12 2006The temporal variability of the telluric sodium layer is investigated by analyzing 28 nights of data obtained with the Colorado State University LIDAR experiment. The mean height power spectrum of the sodium layer was found to be well fit by a power law ... More
Eyemotion: Classifying facial expressions in VR using eye-tracking camerasJul 22 2017Jul 28 2017One of the main challenges of social interaction in virtual reality settings is that head-mounted displays occlude a large portion of the face, blocking facial expressions and thereby restricting social engagement cues among users. Hence, auxiliary means ... 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
Gemini Infrared Multi-Object Spectrograph: Instrument OverviewJul 10 2018Aug 03 2018The Gemini Infrared Multi-Object Spectrograph (GIRMOS) is a powerful new instrument being built to facility-class standards for the Gemini telescope. It takes advantage of the latest developments in adaptive optics and integral field spectrographs. GIRMOS ... More
A Lexicon for Underspecified Semantic TaggingMay 14 1997The paper defends the notion that semantic tagging should be viewed as more than disambiguation between senses. Instead, semantic tagging should be a first step in the interpretation process by assigning each lexical item a representation of all of its ... More
Semiparametric Efficiency of GMM under Approximate ConstraintsNov 22 2010Nov 23 2010Generalized empirical likelihood and generalized method of moments are well spread methods of resolution of inverse problems in econometrics. Each method defines a specific semiparametric model for which it is possible to calculate efficiency bounds. ... More
Discrepancy, separation and Riesz energy of finite point sets on compact connected Riemannian manifoldsMar 26 2014Jun 28 2014On a smooth compact connected $d$-dimensional Riemannian manifold $M$, if $0 < s < d$ then an asymptotically equidistributed sequence of finite subsets of $M$ that is also well-separated yields a sequence of Riesz $s$-energies that converges to the energy ... More
Self-field and magnetic-flux quantum mechanicsApr 06 2005Self-field and quantized magnetic-flux are employed to generate the quantum numbers n, m, and l of atomic physics. Wave-particle duality is shown to be a natural outcome of having a particle and its self-field.
Asyptotic Normality for Maximum Likelihood Estimation and Operational RiskAug 12 2015Aug 25 2016Operational risk models commonly employ maximum likelihood estimation (MLE) to fit loss data to heavy-tailed distributions. Yet several desirable properties of MLE (e.g. asymptotic normality) are generally valid only for large sample-sizes, a situation ... More
Transfert du pseudo-coefficient de Kottwitz et formules de caractere pour la serie discrete de GL(N) d'un corps localMar 30 2012Let G be the group GL(N,F), where F is a non-archimedean locally compact field. Using Bushnell and Kutzko's simple types, as well as an original idea of Henniart's, we construct explicit pseudo-coefficients for the discrete series representations of G. ... More
The equivariant pair-of-pants product in fixed point Floer cohomologyNov 10 2014May 31 2015The Floer cohomology of a symplectic automorphism and that of its square are related by the pair-of-pants product. For exact symplectic automorphisms, we introduce an equivariant version of that product, and use it to prove a Smith-type inequality of ... More
Lagrangian homology spheres in (A_m) Milnor fibres via C^*-equivariant A_infinity modulesFeb 09 2012Aug 08 2012We establish restrictions on Lagrangian embeddings of rational homology spheres into certain open symplectic manifolds, namely the (A_m) Milnor fibres of odd complex dimension. This relies on general considerations about equivariant objects in module ... More
Exact Lagrangian submanifolds of $T^*S^n$ and the graded Kronecker quiverJan 17 2004This short and fairly informal note is an attempt to explain how methods of homological algebra may be brought to bear on problems in symplectic geometry. We do this by looking at a familiar sample question, which is that of the topology of Lagrangian ... More
Homological mirror symmetry for the quartic surfaceOct 26 2003Aug 06 2013This proves Kontsevich's mirror conjecture for (on the symplectic side) a quartic surface in P^3.
Graded Lagrangian submanifoldsMar 09 1999May 31 2000In the usual setup, the grading on Floer homology is relative: it is unique only up to adding a constant. "Graded Lagrangian submanifolds" are Lagrangian submanifolds with a bit of extra structure, which fixes the ambiguity in the grading. The idea is ... More
Disjoinable Lagrangian spheres and dilationsJul 18 2013Oct 20 2013We consider open symplectic manifolds which admit dilations (in the sense previously introduced by Solomon and the author). We obtain restrictions on collections of Lagrangian submanifolds which are pairwise disjoint (or pairwise disjoinable by Hamiltonian ... More
On Those Analytic Functions of One Variable which possess an Algebraic Addition TheoremDec 26 2012This is a literal word-for-word translation from the German of the article by Paul Koebe which contains a proof of Weierstrass's famous theorem characterizing all analytic functions which possess an algebraic addition theorem.
Nesting Induced Large Magnetoelasticity in the Iron Arsenide SystemsDec 17 2013Sep 02 2014A novel feature of the iron arsenides is the magnetoelastic coupling between the long wavelength in-plane strains of the lattice and the collective spin fluctuations of the electrons near the magnetic ordering wavevectors. Here, we study its microscopic ... More
Interaction Correction of Conductivity Near a Ferromagnetic Quantum Critical PointSep 07 2007Nov 05 2008We calculate the temperature dependence of conductivity due to interaction correction for a disordered itinerant electron system close to a ferromagnetic quantum critical point which occurs due to a spin density wave instability. In the quantum critical ... More
Collective flow without hydrodynamics: simulation results for relativistic ion collisionsApr 10 2015Sep 14 2015Flow signatures in experimental data from relativistic ion collisions are usually interpreted as a fingerprint of the presence of a hydrodynamic phase during the evolution of these systems. In this work, flow signatures arising from event-by-event viscous ... More
Causal Viscous Hydrodynamics for Central Heavy-Ion Collisions II: Meson Spectra and HBT RadiiJan 11 2007Feb 16 2007Causal viscous hydrodynamic fits to experimental data for pion and kaon transverse momentum spectra from central Au+Au collisions at \sqrt{s_{NN}}=200 GeV are presented. Starting the hydrodynamic evolution at 1 fm/c and using small values for the relaxation ... More
Hyperspherical Partial Wave Theory with Two-term Error CorrectionFeb 14 2008Hyperspherical Partial Wave Theory has been applied to calculate T-matrix elements and Single Differential Cross-Section (SDCS) results for electron-hydrogen ionization process within Temkin-Poet model potential. We considered three different values of ... More
Recent Physics results with the COMPASS ExperimentNov 03 2005Nov 06 2005The COMPASS experiment has obtained first physics results in the field of polarized distribution functions for quarks and gluons using muon scattering off polarized deuterons. The analysis using open charm production and pairs of high $p_T$ hadrons is ... More
Selected Aspects of Neutron DecayApr 18 2005Precision measurements of neutron decay offer complementary access to particle physics at small distance scales or high energies. In particular they allow tests of the V-A structure of the weak interaction. Among many experimental activities which are ... More
Strangeness in Hadronic SystemsSep 23 1999This paper reviews different aspects of hadronic systems with strange quarks. It reviews production, spectroscopy and decay of baryons and hypernuclei with emphasis on recent results obtained in this field. It includes a comparison of different systems ... More
Generating functions attached to some infinite matricesJun 10 2009Let V be an infinite matrix with rows and columns indexed by the positive integers, and entries in a field F. Suppose that v_{i,j} only depends on i-j and is 0 for |i-j| large. Then V^n is defined for all n, and one has a "generating function" G=\sum ... More
It was twenty years ago today ...Aug 14 2011Sep 13 2011To mark the 20th anniversary of the (14 Aug 1991) commencement of (now, I've adapted this article from one that first appeared in Physics World (2008), was later reprinted (with permission) in Learned Publishing (2009), ... More
Exponentiation of commuting nilpotent varietiesJun 22 2013Sep 20 2014Let $H$ be a linear algebraic group over an algebraically closed field of characteristic $p>0$. We prove that any "exponential map" for $H$ induces a bijection between the variety of $r$-tuples of commuting $[p]$-nilpotent elements in $Lie(H)$ and the ... More
Support Varieties for Frobenius Kernels of Classical GroupsJan 13 2012Sep 26 2012Let G be a simple classical algebraic group over an algebraically closed field of positive characteristic. We describe the support variety of a simple G-module over the r-th Frobenius kernel of G, in terms of its calculation over the first Frobenius kernel. ... More
Compactly generated quasitopological homotopy groups with discontinuous multiplicationMay 31 2011For each positive integer Q there exists a path connected metric compactum X such that the Qth-homotopy group of X is compactly generated but not a topological group (with the quotient topology).
Lemma 4: Haptic Input + Auditory Display = Musical Instrument?Nov 21 2013In this paper we look at some of the design issues that affect the success of multimodal displays that combine acoustic and haptic modalities. First, issues affecting successful sonification design are explored and suggestions are made about how the language ... More
Computing with Hereditarily Finite SequencesDec 16 2011e use Prolog as a flexible meta-language to provide executable specifications of some fundamental mathematical objects and their transformations. In the process, isomorphisms are unraveled between natural numbers and combinatorial objects (rooted ordered ... More
On Two Infinite Families of Pairing BijectionsJan 01 2013We describe two general mechanisms for producing pairing bijections (bijective functions defined from N x N to N). The first mechanism, using n-adic valuations results in parameterized algorithms generating a countable family of distinct pairing bijections. ... More
Declarative Combinatorics: Boolean Functions, Circuit Synthesis and BDDs in HaskellAug 06 2008We describe Haskell implementations of interesting combinatorial generation algorithms with focus on boolean functions and logic circuit representations. First, a complete exact combinational logic circuit synthesizer is described as a combination of ... More
Pairing Functions, Boolean Evaluation and Binary Decision Diagrams in PrologAug 05 2008Feb 04 2009A "pairing function" J associates a unique natural number z to any two natural numbers x,y such that for two "unpairing functions" K and L, the equalities K(J(x,y))=x, L(J(x,y))=y and J(K(z),L(z))=z hold. Using pairing functions on natural number representations ... More
Provably Manipulation-Resistant Reputation SystemsNov 05 2014We consider a community of users who must make periodic decisions about whether to interact with one another. We propose a protocol which allows honest users to reliably interact with each other, while limiting the damage done by each malicious or incompetent ... More
Just How Final are Today's Quantum Structures?Mar 26 2001I present a selection of conceptual and mathematical problems in the foundations of modern physics as they derive from the title question. Contribution to a panel session, "Springer Forum: Quantum Structures -- Physical, Mathematical and Epistemological ... More
The Hawaiian earring group and metrizabilityMar 10 2006Endowed with quotient topology inherited from the space of based loops, the fundamental group of the Hawaiian earring fails to be metrizable. The fundamental group of any space which retracts to the Hawaiian earring is also nonmetrizable.
Absolute Algebra III - The saturated spectrumOct 31 2013Let B1 denote the set {0,1} with the usual operations except that $1+1=1$, in other words, the smallest characteristic 1 semifield . We compare two possible analogues of the notion of prime ideal for B1--algebras. We then consider the relations between ... More
Algèbre absolueNov 10 2009We give an exposition of Zhu's theory concerning a formal analogue of the field Fp, "for p = 1", and then compare it to Deitmar's.-- Nous exposons la th\'eorie de Zhu concernant un analogue formel du corps Fp "pour p = 1", et la comparons \`a celle de ... More
Qualitative Decision Making Under Possibilistic Uncertainty: Toward more discriminating criteriaJul 04 2012The aim of this paper is to propose a generalization of previous approaches in qualitative decision making. Our work is based on the binary possibilistic utility (PU), which is a possibilistic counterpart of Expected Utility (EU).We first provide a new ... More
The Evolution of AGN in Groups and ClustersOct 08 2009The evolution of AGN in groups and clusters provides important information about how their black holes grow, the extent to which galaxies and black holes coevolve in dense environments, and has implications for feedback in the local universe and at the ... More
Symplectic packing in dimension 4Jun 06 1996Jun 09 1996We discuss closed symplectic 4-manifolds which admit full symplectic packings by $N$ equal balls for large $N$'s. We give a homological criterion for recognizing such manifolds. As a corollary we prove that ${\Bbb C}P^2$ can be fully packed by $N$ equal ... More
Noncommutative String Theory, the R-Matrix, and Hopf AlgebrasNov 04 1999Motivated by the form of the noncommutative *-product in a system of open strings and Dp-branes with constant nonzero Neveu-Schwarz 2-form, we define a deformed multiplication operation on a quasitriangular Hopf algebra in terms of its R-matrix, and comment ... More
Ward Identities and Anomalies in Pure W_4 GravitySep 11 1998Feb 12 1999W_4 gravity is treated algebraically, represented by a set of transformations on classical fields. The Ward identities of the theory are determined by requiring the algebra to close. The general forms for the anomalies are found by looking for solutions ... More
Derivatives and the Role of the Drinfel'd Twist in Noncommutative String TheoryMar 26 2000Mar 29 2000We consider the derivatives which appear in the context of noncommutative string theory. First, we identify the correct derivations to use when the underlying structure of the theory is a quasitriangular Hopf algebra. Then we show that this is a specific ... More
Effects of mathematical locality and number scaling on coordinate chart useMay 13 2014A stronger foundation for earlier work on the effects of number scaling, and local mathematics is described. Emphasis is placed on the effects of scaling on coordinate systems. Effects of scaling are represented by a scalar field, $\theta,$ that appears ... More
Fields of Iterated Quantum Reference Frames based on Gauge Transformations of Rational String StatesApr 18 2006This work is based on a description of quantum reference frames that seems more basic than others in the literature. Here a frame is based on a set of real and of complex numbers and a space time as a 4-tuple of the real numbers. There are many isomorphic ... More
A representation of complex rational numbers in quantum mechanicsMar 16 2005Jun 20 2005A representation of complex rational numbers in quantum mechanics is described that is not based on logical or physical qubits. It stems from noting that the zeros in a product qubit state do not contribute to the number. They serve only as place holders. ... More
Tightening the Theory-Experiment Connection in Physics: R_{n} based Space and TimeAug 11 2004Some aspects of replacing C based physics by C_{n} based physics are discussed. Here C_{n} ={R_{n},I_{n}} where R_{n} and I_{n} are the real and imaginary components of the numbers in C_{n}, and both R_{n} and I_{n}) are sets of length 2n string numbers ... More
The Representation of Numbers by States in Quantum MechanicsSep 29 2000The representation of numbers by tensor product states of composite quantum systems is examined. Consideration is limited to k-ary representations of length L and arithmetic modulo k^{L}. An abstract representation on an L fold tensor product Hilbert ... More
Dynamics of Induced Surfaces in Four-Dimensional Euclidean SpaceDec 15 2006The Davey Stewartson hierarchy will be developed based on a set of three matrix differential operators. These equations will act as evolution equations for different types of surface deformation in Euclidean four space. The Weierstrass representation ... More
Closed Unitary and Similarity Orbits of Normal Operators in Purely Infinite C*-AlgebrasAug 31 2012Nov 29 2012We will investigate the norm closure of the unitary and similarity orbits of normal operators in unital, simple, purely infinite C*-algebras. An operator theoretic proof will be given to the classification of when two normal operators are approximately ... More
Cyclic MonopolesOct 06 1996We study charge k SU(2) BPS monopoles which are symmetric under the cyclic group of order k. Approximate twistor data (spectral curves and Nahm data) is constructed using a new technique based upon a Painleve analysis of Nahm's equation around a pole. ... More
Knots in the Skyrme-Faddeev modelMay 10 2007The Skyrme-Faddeev model is a modified sigma model in three-dimensional space, which has string-like topological solitons classified by the integer-valued Hopf charge. Numerical simulations are performed to compute soliton solutions for Hopf charges up ... More
Kink Chains from Instantons on a TorusSep 29 1994We describe how the procedure of calculating approximate solitons from instanton holonomies may be extended to the case of soliton crystals. It is shown how sine-Gordon kink chains may be obtained from CP1 instantons on a torus. These kink chains turn ... More
Spanning Trees in Grid GraphsSep 15 2008Building on work by Desjarlais, Molina, Faase, and others, a general method is obtained for counting the number of spanning trees of graphs that are a product of an arbitrary graph and either a path or a cycle, of which grid graphs are a subclass. Results ... More
Analyticity of strictly static and strictly stationary, inheriting and non-inheriting Einstein-Maxwell solutionsApr 19 2007Following the technique of M\"uller-zum-Hagen, refs [1,2], we show that strictly static and strictly stationary solutions of the Einstein-Maxwell equations are analytic in harmonic coordinates. This holds whether or not the Maxwell field inherits the ... More
A comment on positive mass for scalar field sourcesMay 31 2011We use a transformation due to Bekenstein to relate the ADM and Bondi masses of asymptotically-flat solutions of the Einstein equations with, respectively, scalar sources and conformal-scalar sources. Although the conformal-scalar energy-momentum tensor ... More
Conditions for nonexistence of static or stationary, Einstein-Maxwell, non-inheriting black-holesNov 05 2006We consider asymptotically-flat, static and stationary solutions of the Einstein equations representing Einstein-Maxwell space-times in which the Maxwell field is not constant along the Killing vector defining stationarity, so that the symmetry of the ... More
A Note on Riemannian Anti-self-dual Einstein metrics with SymmetrySep 11 2006We give a complete proof of the result stated in an earlier article, that the general Einstein metric with a symmetry, an anti-self-dual Weyl tensor and nonzero scalar curvature is determined by a solution of the $SU(\infty)$-Toda field equation. We consider ... More
Two linear transformations each tridiagonal with respect to an eigenbasis of the otherJun 27 2004Let $K$ denote a field and let $V$ denote a vector space over $K$ with finite positive dimension. We consider a pair of linear transformations $A:V\to V$ and $A^*:V\to V$ that satisfy both conditions below: (i) There exists a basis for $V$ with respect ... More
GL(2,R)-Invariant Measures in Marked Strata: Generic Marked Points, Earle-Kra for Strata, and IlluminationJan 28 2016Let H be a component of a stratum of abelian differentials and let H(m,n) be the collection of translation surfaces in H together with m+n distinct marked points, none coinciding with zeros, m of which are labelled and n of which are unlabelled. We show ... More
On Integrability of Type 0A Matrix Model in the Presence of D braneJan 11 2011We consider type 0A matrix model in the presence of a spacelike D brane,localized in matter direction at any arbitrary point. It appears that in order to have an appropriate string/MQM correspondence we must need to impose a constraint on the matrix model ... More
Parton Propagation in a Gluon FieldFeb 22 2005The phenomenological success of PQCD is based on processes where the effects of the color field environment on parton propagation can be eliminated or is universal. In hard diffraction and quarkonium production the PQCD subprocess is the same as in fully ... More
The Unexpected Role of Final State Interactions in Deep Inelastic ScatteringJul 21 2003Rescattering of the struck quark in Deep Inelastic Scattering implies that measured parton distributions are not directly related to the Fock state probabilities of the target wave function. The production amplitudes acquire dynamical phases, which gives ... More
Confinement with Perturbation Theory, after All?Sep 16 2014Nov 17 2014I call attention to the possibility that QCD bound states (hadrons) could be derived using rigorous Hamiltonian, perturbative methods. Solving Gauss' law for $A^0$ with a non-vanishing boundary condition at spatial infinity gives an \order{\alpha_s^0} ... More
Are hadrons simpler than they seem?Mar 07 2013I briefly review a systematic approximation scheme of QCD in which the quark model picture of hadrons emerges at lowest order. A linear A^0 potential arises if Gauss' law is solved with a non-vanishing boundary condition at spatial infinity. Similarly ... More
Measuring transverse size with virtual photonsOct 15 2011Fourier transforming the virtual photon transverse momentum in \gamma*(q)+N \to f processes allows new insight into hadron dynamics as a function of impact parameter b. I discuss how previous analyses of charge density based on elastic and transition ... More
Soft Perturbative QCDAug 30 1999There are indications of a faith transition in QCD: The strong coupling may freeze at a sufficiently low value to make PQCD relevant even in the confining regime. The properties of PQCD at low Q^2 depend on the asymptotic field configuration assumed at ... More
A New Class of Asymptotically Non-Chaotic Vacuum SingularitiesJul 15 2015Dec 10 2015The BKL conjecture, stated in the 60s and early 70s by Belinski, Khalatnikov and Lifshitz, proposes a detailed description of the generic asymptotic dynamics of spacetimes as they approach a spacelike singularity. It predicts complicated chaotic behaviour ... More