Results for "D. L. Walker"

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Affine Hecke algebras of type D and generalisations of quiver Hecke algebrasJan 28 2019We define and study cyclotomic quotients of affine Hecke algebras of type D. We establish an isomorphism between (direct sums of blocks of) these cyclotomic quotients and a generalisation, for type D, of cyclotomic quiver Hecke algebras which are a family ... More
Light Propagation Effects In QED: Effective Action ApproachMar 06 2006The effects of light propagation in constant magnetic and electric backgrounds are considered in the framework of the effective action approach. We use the exact analytic series representation for the one-loop effective action of QED and apply it to the ... More
Monopole Condensation and Dimensional Transmutation in SU(2) QCDSep 25 2002Sep 24 2004We resolve the controversy on the stability of the monopole condensation in the one-loop effective action of SU(2) QCD by calculating the imaginary part of the effective action with two different methods at one-loop order. Our result confirms that the ... More
Intermediate energy spectrum of five colour QCD at one loopOct 10 2007I consider the monopole condensate of five colour QCD. The naive lowest energy state is unobtainable at one-loop for five or more colours due to simple geometry. The consequent adjustment of the vacuum condensate generates a hierarchy of confinement scales ... More
Higgs-free confinement hierarchy in five colour QCDJul 18 2007Sep 27 2007I consider the monopole condensate of five color QCD. The naive lowest energy state is unobtainable at one-loop for five or more colors due to simple geometric considerations. The consequent adjustment of the vacuum condensate generates a hierarchy of ... More
Extending SU(2) to SU(N) QCDJun 27 2007Jul 30 2007Abelian dominance is used to reformulate the QCD Lagrangian as a sum over the roots of Lie group representation theory. This greatly facilitates extending the SU(2) magnetic ground state energy spectrum, several arguments for the stability of the magnetic ... More
Supersymmetry and Chiral SymmetryDec 14 1999We dispute a recent claim for a nonperturbative nonrenormalisation theorem stating that mass cannot be spontaneously generated in supersymmetric QED. We also extend a long-standing perturbative result, namely that the effective potential is zero to all ... More
Isotropic and Gauge Invariant Monopole Condensation in SU(2) QCDMar 21 2007Feb 28 2008I construct an isotropic, gauge invariant monopole condensate in SU(2) QCD. It provides a suitable, gauge-invariant vacuum for the dual-Meissner effect to provide QCD colour confinement without violating the isotropy of real space.
Three point SUSY Ward identities without GhostsAug 18 2004Sep 10 2004We utilise a non-local gauge transform which renders the entire action of SUSY QED invariant and respects the SUSY algebra modulo the gauge-fixing condition, to derive two- and three-point ghost-free SUSY Ward identities in SUSY QED. We use the cluster ... More
A Completely Invariant SUSY Transform of Supersymmetric QEDOct 10 2003We study the SUSY breaking of the covariant gauge-fixing term in SUSY QED and observe that this corresponds to a breaking of the Lorentz gauge condition by SUSY. Reasoning by analogy with SUSY's violation of the Wess-Zumino gauge, we argue that the SUSY ... More
Gluonic Colour Singlets in QCDAug 30 2009Jul 15 2010We argue that certain specific gluon excitations, other than conventional glueballs, can propagate freely outside of hadrons and glueballs. We begin with the result that the Abelian generators of $SU(N)$ QCD can be meaningfully isolated by the Cho-Faddeev-Niemi-Shabanov ... More
Stability of the Magnetic Monopole Condensate in three- and four-colour QCDMay 10 2006Jan 02 2007It is argued that the ground state of three- and four-colour QCD contains a monopole condensate, necessary for the dual Meissner effect to be the mechanism of confinement, and support its stability on the grounds that it gives the off-diagonal gluons ... More
Superluminal Near-field Dipole Electromagnetic FieldsJan 26 2000The purpose of this paper is to present mathematical evidence that electromagnetic near-field waves and wave groups, generated by an oscillating electric dipole, propagate much faster than the speed of light as they are generated near the source, and ... More
Nearfield Electromagnetic Effects on Einstein Special RelativityFeb 20 2007In this paper Maxwell equations are used to analyze the propagation of oscillating electric and magnetic fields from a moving electric dipole source. The results show that both the magnetic field and electric fields generated propagate faster than the ... More
Hall Algebras as Hopf ObjectsNov 24 2010One problematic feature of Hall algebras is the fact that the standard multiplication and comultiplication maps do not satisfy the bialgebra compatibility condition in the underlying symmetric monoidal category Vect. In the past this problem has been ... More
Superluminal Electromagnetic and Gravitational Fields Generated in the Nearfield of Dipole SourcesMar 28 2006In this paper the fields generated by an electric dipole and a gravitational quadrapole are shown to propagate superluminally in the nearfield of the source and reduce to the speed of light as the fields propagate into the farfield. A theoretical derivation ... More
Near-field Analysis of Superluminally Propagating Electromagnetic and Gravitational FieldsApr 23 2003A near-field analysis based on Maxwells equations is presented which indicates that the fields generated by both an electric and a magnetic dipole or quadrapole, and also the gravitational waves generated by a quadrapole mass source propagate superluminally ... More
Experimental Evidence of Near-field Superluminally Propagating Electromagnetic FieldsSep 06 2000A simple experiment is presented which indicates that electromagnetic fields propagate superluminally in the near-field next to an oscillating electric dipole source. A high frequency 437MHz, 2 watt sinusoidal electrical signal is transmitted from a dipole ... More
Theoretical, Numerical, and Experimental Evidence of Superluminal Electromagnetic and Gravitational Fields Generated in the Nearfield of Dipole SourcesAug 23 2005Theoretical and numerical wave propagation analysis of an oscillating electric dipole is presented. The results show that upon creation at the source, both the longitudinal electric and transverse magnetic fields propagate superluminally and reduce to ... More
Analysis of Causality Issue in Near-field Superluminally Propagating Electromagnetic and Gravitational FieldsSep 26 2000A simple relativistic analysis is presented which shows that near-field superluminal longitudinal electric signals generated by an electric dipole cannot be used to violate Einstein causality by using the relativistic "sync shift" effect. The analysis ... More
Measuring the Edwards-Anderson order parameter of the Bose glass: a quantum gas microscope approachJul 18 2016With the advent of spatially resolved fluorescence imaging in quantum gas microscopes, it is now possible to directly image glassy phases and probe the local effects of disorder in a highly controllable setup. Here we present numerical calculations using ... More
Measuring the Edwards-Anderson order parameter of the Bose glass: a quantum gas microscope approachJul 18 2016Oct 24 2016With the advent of spatially resolved fluorescence imaging in quantum gas microscopes, it is now possible to directly image glassy phases and probe the local effects of disorder in a highly controllable setup. Here we present numerical calculations using ... More
Scaling of the Hall Resistivity in the Solid and Liquid Vortex Phases in Twinned Single Crystal YBCONov 07 1998Jun 18 1999Longitudinal and Hall voltages are measured in a clean twinned YBCO single crystal in the liquid and solid vortex phases. For magnetic fields tilted away from the c-axis more than about 2 deg, a scaling law |rho_xy|=A (rho_xx)^beta with beta approx.=1.4 ... More
Hall Anomaly and Vortex-Lattice Melting in Superconducting Single Crystal YBa2Cu3O7-dAug 15 1998Sub-nanovolt resolution longitudinal and Hall voltages are measured in an ultra pure YBa2Cu3O7-d single crystal. The Hall anomaly and the first-order vortex-lattice melting transition are observed simultaneously. Changes in the dynamic behavior of the ... More
Finite Element Analysis of Magnetic Microparticle Induced Strain on a Fibrin Matrix due to the Influence of an Electromagnetic FieldNov 02 2016Blood clots occur in the human body when they are required to prevent bleeding. In pathological states such as diabetes and sickle cell disease, blood clots can also form undesirably due to hypercoagulable plasma conditions. With the continued effort ... More
Electromagnetically Induced Distortion of a Fibrin Matrix with Embedded MicroparticlesNov 02 2016Jan 23 2018Blood clots occur in the human body when they are required to prevent bleeding. In pathological states such as diabetes and sickle cell disease, blood clots can also form undesirably due to hypercoagulable plasma conditions. With the continued effort ... More
Origin of the Hall conductivity below the vortex-lattice melting in twinned single crystal YBCOOct 15 1998In his the Comment, P. Ao affirms that his vortex many-body theory explains the observations reported in G. D'Anna et al., Phys. Rev. Lett. 81, 2530 (1998). Indeed, we provide here some arguments to show the lack of a satisfactory explanation within the ... More
Electron transport in the dye sensitized nanocrystalline cellJul 26 2001Dye sensitised nanocrystalline solar cells (Gr\"{a}tzel cells) have achieved solar-to-electrical energy conversion efficiencies of 12% in diffuse daylight. The cell is based on a thin film of dye-sensitised nanocrystalline TiO$_2$ interpenetrated by a ... More
Matched Metrics and ChannelsJun 11 2015The most common decision criteria for decoding are maximum likelihood decoding and nearest neighbor decoding. It is well-known that maximum likelihood decoding coincides with nearest neighbor decoding with respect to the Hamming metric on the binary symmetric ... More
Asymmetric, Closed-Form, Finite-Parameter Models of Multinomial ChoiceJun 19 2016Feb 09 2018In transportation, the number of observations associated with one discrete outcome is often greatly different from the number of observations associated with another discrete outcome. This situation is known as class-imbalance. In statistics, one hypothesized ... More
Cho-Duan-Ge decomposition of QCD in the constraintless Clairaut-type formalismNov 23 2014Mar 15 2015We apply the recently derived constraintless Clairaut-type formalism to the Cho-Duan-Ge decomposition in SU(2) QCD. We find nontrivial corrections to the physical equations of motion and that the contribution of the topological degrees of freedom is qualitatively ... More
Propagation Speed of Longitudinally Oscillating Gravitational and Electrical FieldsJun 27 1997Jul 28 1997The near-field Lienard-Wiechert potential solution of a longitudinally oscillating electrical field produced by an oscillating charge is presented, and the results are compared to the R. P. Feynman multipole far-field solution. The results indicate that ... More
Circularly polarised X-rays as a probe of non-collinear magnetic order in multiferroic TbMnO3May 19 2009Non-resonant X-ray magnetic scattering has been used to study the magnetic structure of multiferroic TbMnO3 in its ferroelectric phase. Circularly polarized X-rays were combined with a full polarization analysis of the scattered beam to reveal important ... More
Rabi flopping between ground and Rydberg states with dipole-dipole atomic interactionsNov 02 2007We demonstrate Rabi flopping of small numbers of $\rm{^{87}Rb}$ atoms between ground and Rydberg states with $n\le 43$. Coherent population oscillations are observed for single atom flopping, while the presence of two or more atoms decoheres the oscillations. ... More
Circularly Polarised X-ray Scattering Investigation of Spin-Lattice Coupling in TbMnO$_3$ in Crossed Electric and Magnetic FieldsNov 26 2013Jan 10 2014We present a study of the magnetic and crystallographic structure of TbMnO$_3$ in the presence of crossed electric and magnetic fields using circularly polarised X-ray non-resonant scattering. A comprehensive account is presented of the scattering theory ... More
Observation of Rydberg blockade between two atomsMay 06 2008We demonstrate experimentally that a single Rb atom excited to the $79d_{5/2}$ level blocks the subsequent excitation of a second atom located more than $10 \mu\rm m$ away. The observed probability of double excitation of $\sim 30%$ is consistent with ... More
Spin Relaxation Resonances Due to the Spin-Axis Interaction in Dense Rubidium and Cesium VaporSep 25 2000Resonances in the magnetic decoupling curves for the spin relaxation of dense alkali-metal vapors prove that much of the relaxation is due to the spin-axis interaction in triplet dimers. Initial estimates of the spin-axis coupling coefficients for the ... More
PKS 0405--385: the smallest radio quasar?Oct 06 1997We have observed profound variability in the radio flux density of the quasar PKS 0405-385 on timescales of less than an hour; this is unprecedented amongst extragalactic sources. If intrinsic to the source, these variations would imply a brightness temperature ... More
Nonperturbative Vertices in Supersymmetric Quantum ElectrodynamicsApr 21 1999We derive the complete set of supersymmetric Ward identities involving only two- and three- point proper vertices in supersymmetric QED. We also present the most general form of the proper vertices consistent with both the supersymmetric and U(1) gauge ... More
Stability of Monopole Condensation in SU(2) QCDJun 14 2002Sep 24 2004We propose to resolve the controversy regarding the stability of the monopole condensation in QCD by calculating the imaginary part of the one-loop effective action perturbatively. We calculate the imaginary part perturbatively to the order $g^2$ with ... More
Chiral Symmetry in Supersymmetric Three Dimensional Quantum ElectrodynamicsJan 17 1999Mar 17 1999We describe the investigation of spontaneous mass-generation and chiral symmetry breaking in supersymmetric QED3 using numerical solutions of the Dyson-Schwinger equation together with the CJT effective action and supersymmetric Ward identities. We find ... More
U(2)-chiral symmetries of supersymmetric QED3Mar 14 1997Jun 23 1997Supersymmetry is studied in 2+1 dimensions. In addition to the multiplets corresponding to those in 3+1 dimensions the Clifford algebra allows an extra set. When the extra chiral multiplet is included, formulating supersymmetric QED3 in the manner of ... More
Machine Learning Meets Microeconomics: The Case of Decision Trees and Discrete ChoiceNov 13 2017We provide a microeconomic framework for decision trees: a popular machine learning method. Specifically, we show how decision trees represent a non-compensatory decision protocol known as disjunctions-of-conjunctions and how this protocol generalizes ... More
Evidence for new unidentified TeV gamma-ray sources from angularly-correlated hot-spots observed by independent TeV gamma-ray sky surveysAug 31 2004We have examined the directional cross-correlation of statistical `hot-spots' between a Northern Sky TeV Gamma Ray Survey by the Milagro Observatory and a similar survey by the Tibet Array. We find the directions of these hot-spots are angularly uncorrelated ... More
Gravitational Forces with Strongly Localized RetardationOct 22 1996Nov 12 1996We solve the linearized Einstein equations for a specific oscillating mass distribution and discuss the usual counterarguments against the existence of observable gravitational retardations in the "near zone", where d/r << 1 (d = oscillation amplitude ... More
Antiferromagnetic order and domains in Sr3Ir2O7 probed by x-ray resonant scatteringJan 06 2012This article reports a detailed x-ray resonant scattering study of the bilayer iridate compound, Sr3Ir2O7, at the Ir L2 and L3 edges. Resonant scattering at the Ir L3 edge has been used to determine that Sr3Ir2O7 is a long-range ordered antiferromagnet ... More
K2 Variable Catalogue: Variable Stars and Eclipsing Binaries in K2 Campaigns 1 and 0Feb 13 2015Jun 26 2015We have created a catalogue of variable stars found from a search of the publicly available K2 mission data from Campaigns 1 and 0. This catalogue provides the identifiers of 8395 variable stars, including 199 candidate eclipsing binaries with periods ... More
Ultra-Low-Power Hybrid Light-Matter SolitonsSep 02 2014New functionalities in nonlinear optics will require systems with giant optical nonlinearity as well as compatibility with photonic circuit fabrication techniques. Here we introduce a new platform based on strong light-matter coupling between waveguide ... More
K2 Variable Catalogue I: A Catalogue of Variable Stars from K2 Field 0Nov 25 2014Jan 08 2015We have searched the K2 campaign 0 data for lightcurve variations associated with stellar variability. The results of this search are presented as a catalogue, giving the identifiers of nearly 2500 variable stars in the dataset. We list the detected range ... More
Surface superconductivity and order parameter suppression in UPt$_3$Sep 05 1995We show that a recent measurement of surface superconductivity in UPt$_3$ (Keller {\it et. al.}, Phys. Rev. Lett. {\bf 73}, 2364 (1994)) can be understood if the superconducting pair wavefunction is suppressed anisotropically at a vacuum to superconductor ... More
Molecular Disk Properties in Early-Type GalaxiesAug 12 2010We study the simulated CO emission from elliptical galaxies formed in the mergers of gas-rich disk galaxies. The cold gas not consumed in the merger-driven starburst quickly resettles into a disk-like configuration. By analyzing a variety of arbitrary ... More
Multiplicity Distribution and Mechanisms of the High-Energy Hadron CollisionsJan 05 1998We discuss the multiplicity distribution for highest accessible energies of $pp$- and $\bar pp$- interactions from the point of view of the multiparton collisions. The inelastic cross sections for the single, $\sigma_1$, and multiple (double and, presumably, ... More
Flipping SU(5) out of TroubleMay 30 2002Minimal supersymmetric SU(5) GUTs are being squeezed by the recent values of alpha_s, sin^2 theta_W, the lower limit on the lifetime for p to nubar K decay, and other experimental data. We show how the minimal flipped SU(5) GUT survives these perils, ... More
Is Computation Reversible?Jan 16 2004Recent investigations into the physical nature of information and fundamental limits to information transmission have revealed questions such as the possibility of superluminal data transfer or not; and whether reversible computation (information processing) ... More
Information Transfer Time: The Role of Holomorphism, Stationary Phase, and NoiseOct 28 2002In this paper we present an analysis of information transfer time based on holomorphism, causality and the classical principle of stationary phase. We also make a preliminary study of the effect of noise on information transfer time, and find that noise ... More
Information Transfer and Landauer's PrincipleOct 23 2003In this paper we present an analysis of information transfer based on Landauer's principle (i.e. erasure of information is associated with an increase in entropy), as well as considerations of analyticity and causality. We demonstrate that holomorphic ... More
A Dynamic Theory of Information and EntropyMay 06 2004We propose a new thermodynamic, relativistic relationship between information and entropy, which is closely analogous to the classic Maxwell electro-magnetic equations. Determination of whether information resides in points of non-analyticity or is more ... More
Contamination of stellar-kinematic samples and uncertainty about dark matter annihilation profiles in ultrafaint dwarf galaxies: the example of Segue IJun 26 2015Aug 09 2016The expected gamma-ray flux coming from dark matter annihilation in dwarf spheroidal (dSph) galaxies depends on the so-called `J-factor', the integral of the squared dark matter density along the line-of-sight. We examine the degree to which estimates ... More
Effect of diffusive boundaries on surface superconductivity in unconventional superconductorsMay 07 1996Boundary conditions for a superconducting order parameter at a diffusive scattering boundary are derived from microscopic theory. The results indicate that for all but isotropic gap functions the diffusive boundary almost completely suppresses surface ... More
Diffuse Molecular Clouds and the Molecular Interstellar Medium from 13CO Observations of M33Mar 04 1994We have obtained 12CO and 13CO J=1-0 observations of the nearby spiral galaxy M33 to try to resolve the long-standing discrepancy between 12CO/13CO line ratios measured in Galactic giant molecular clouds and external galaxies. Interferometer maps of the ... More
Ho and Fe magnetic ordering in multiferroic HoFe3(BO3)O4Apr 04 2013Resonant and non-resonant X-ray scattering studies on HoFe3(BO3)O4 reveal competing magnetic ordering of Ho and Fe moments. Temperature and X-ray polarization dependent measurements employed at the Ho L3 edge directly reveal a spiral spin order of the ... More
Big fish, small fish: Two New Ultra-Faint Satellites of the Milky WayFeb 02 2010We report the discovery of two new Milky Way satellites in the neighboring constellations of Pisces and Pegasus identified in data from the Sloan Digital Sky Survey. Pisces II, an ultra-faint dwarf galaxy lies at the distance of ~180 kpc, some 15 degrees ... More
Thirty Meter Telescope Site Testing I: OverviewApr 07 2009As part of the conceptual and preliminary design processes of the Thirty Meter Telescope (TMT), the TMT site testing team has spent the last five years measuring the atmospheric properties of five candidate mountains in North and South America with an ... More
Exploring X-ray Binary Populations in Compact Group Galaxies with $Chandra$Dec 08 2015We obtain total galaxy X-ray luminosities, $L_X$, originating from individually detected point sources in a sample of 47 galaxies in 15 compact groups of galaxies (CGs). For the great majority of our galaxies, we find that the detected point sources most ... More
Femtoscale magnetically induced lattice distortions in multiferroic TbMnO3Oct 13 2011Magneto-electric multiferroics exemplified by TbMnO3 possess both magnetic and ferroelectric long-range order. The magnetic order is mostly understood, whereas the nature of the ferroelectricity has remained more elusive. Competing models proposed to ... More
Tracing the Conversion of Gas into Stars in Young Massive Cluster ProgenitorsFeb 12 2015Whilst young massive clusters (YMCs; $M$ $\gtrsim$ 10$^{4}$ M$_{\odot}$, age $\lesssim$ 100 Myr) have been identified in significant numbers, their progenitor gas clouds have eluded detection. Recently, four extreme molecular clouds residing within 200 ... More
Comparing Young Massive Clusters and their Progenitor Clouds in the Milky WayFeb 08 2016Young massive clusters (YMCs) have central stellar mass surface densities exceeding $10^{4} M_{\odot} pc^{-2}$. It is currently unknown whether the stars formed at such high (proto)stellar densities. We compile a sample of gas clouds in the Galaxy which ... More
Effect of photonic spin-orbit coupling on the topological edge modes of a Su-Schrieffer-Heeger chainDec 05 2018We study the effect of photonic spin-orbit coupling (SOC) in micropillar lattices on the topological edge states of a one-dimensional chain with a zigzag geometry, corresponding to the Su-Schrieffer-Heeger model equipped with an additional internal degree ... More
Observations and modeling of the inner disk region of T Tauri starsDec 16 2004We present observations of four T Tauri stars using long baseline infrared interferometry from the Palomar Testbed Interferometer. The target sources, T Tau N, SU Aur, RY Tau and DR Tau, are all known to be surrounded by dusty circumstellar disks. The ... More
The Cepheids of NGC1866: A Precise Benchmark for the Extragalactic Distance Scale and Stellar Evolution from Modern UBVI PhotometryJan 25 2016We present the analysis of multiband time-series data for a sample of 24 Cepheids in the field of the Large Magellanic Cloud cluster NGC1866. Very accurate BVI VLT photometry is combined with archival UBVI data, covering a large temporal window, to obtain ... More
Physical Parameters of Asteroids Estimated from the WISE 3 Band Data and NEOWISE Post-Cryogenic SurveyOct 01 2012Enhancements to the science data processing pipeline of NASA's Wide-field Infrared Explorer (WISE) mission, collectively known as NEOWISE, resulted in the detection of $>$158,000 minor planets in four infrared wavelengths during the fully cryogenic portion ... More
Detection Limits from the McDonald Observatory Planet Search ProgramApr 07 2006Based on the long-term radial-velocity surveys carried out with the McDonald Observatory 2.7m Harlan J. Smith Telescope from 1988 to the present, we derive upper limits to long-period giant planet companions for 31 nearby stars. Data from three phases ... More
First results from the ATCA 18 GHz pilot surveyJul 07 2004Jul 09 2004As a pilot study for the first all-sky radio survey at short wavelengths, we have observed 1216 sq. deg. of the southern sky at 18GHz (16mm) using a novel wide-band (3.4GHz bandwidth) analogue correlator on one baseline of the Australia Telescope Compact ... More
The Density and Temperature of Molecular Clouds in M33Jan 30 1997We have observed the $^{12}$CO J=2-1, J=3-2, and $^{13}$CO J=2-1 lines in a sample of seven giant molecular clouds in the Local Group spiral galaxy M33. The $^{12}$CO/$^{13}$CO J=2-1 line ratio is constant across the entire sample, while the observed ... More
Electric field control of multiferroic domains in Ni$_3$V$_2$O$_8$ imaged by X-ray polarization enhanced topographyApr 26 2010The magnetic structure of multiferroic Ni$_3$V$_2$O$_8$ has been investigated using non-resonant X-ray magnetic scattering. Incident circularly polarized X-rays combined with full polarization analysis of the scattered beam is shown to yield high sensitivity ... More
The Star Formation Rate - Dense Gas Relation in Galaxies as Measured by HCN (3-2) EmissionMay 28 2008We present observations made with the 10m Heinrich Hertz Sub-Millimeter Telescope of HCN (3-2) emission from a sample of 30 nearby galaxies ranging in infrared luminosity from 10^10 - 10^12.5 L_sun and HCN (3-2) luminosity from 10^6 - 10^9 K km s^-1 pc^2. ... More
VLBI observations of weak sources using fast frequency switchingDec 21 2004Dec 21 2004We have developed a new phase referencing technique for high frequency VLBI observations. In conventional phase referencing, one interleaves short scans on a nearby phase calibrator between the target source observations. In fast frequency switching described ... More
Virtual-to-Real-World Transfer Learning for Robots on Wilderness TrailsJan 17 2019Robots hold promise in many scenarios involving outdoor use, such as search-and-rescue, wildlife management, and collecting data to improve environment, climate, and weather forecasting. However, autonomous navigation of outdoor trails remains a challenging ... More
Using a Primordial Gravitational Wave Background to Illuminate New PhysicsDec 18 2018Feb 16 2019A primordial spectrum of gravitational waves serves as a backlight to the relativistic degrees of freedom of the cosmological fluid. Any change in the particle physics content, due to a change of phase or freeze-out of a species, will leave a characteristic ... More
VLBI detections of a source weaker than 100 mJy at 86 GHzSep 27 2004We use a new phase-calibration strategy to calibrate the phase of 86 GHz VLBI observations of the FR I radio galaxy NGC 4261. Instead of switching between a calibrator source and the target source, the target was observed while rapidly switching between ... More
Near-IR adaptive optics imaging of nuclear spiral structure in the Seyfert galaxy, NGC3227Dec 01 1999We present high spatial resolution, near-IR images in J, H, K of the nucleus of NGC3227, obtained with the Adaptive Optics bonnette on CFHT. The ~0.15 arcsec (17pc) resolution allows structures to be probed in the core region. Dust obscuration becomes ... More
Sure success partial searchMar 15 2006Partial search has been proposed recently for finding the target block containing a target element with fewer queries than the full Grover search algorithm which can locate the target precisely. Since such partial searches will likely be used as subroutines ... More
Using a Primordial Gravitational Wave Background to Illuminate New PhysicsDec 18 2018A primordial spectrum of gravitational waves serves as a backlight to the relativistic degrees of freedom of the cosmological fluid. Any change in the particle physics content, due to a change of phase or freeze-out of a species, will leave a characteristic ... More
Understanding the different rotational behaviors of $^{252}$No and $^{254}$NoApr 25 2012Jun 20 2012Total Routhian surface calculations have been performed to investigate rapidly rotating transfermium nuclei, the heaviest nuclei accessible by detailed spectroscopy experiments. The observed fast alignment in $^{252}$No and slow alignment in $^{254}$No ... More
A search for p-modes and other variability in the binary system 85 Pegasi using MOST photometryJul 11 2009Context: Asteroseismology has great potential for the study of metal-poor stars due to its sensitivity to determine stellar ages. Aims: Our goal was to detect p-mode oscillations in the metal-poor sub-dwarf 85 Peg A and to search for other variability ... More
Modeling the 3C 120 Radio Jet from 1 to 30 MilliarcsecondsOct 29 2004The predicted spatial development of helical structures along an expanding jet are used to model observed structures and motions in the 3C 120 jet. Proper motions of helical components associated with the pattern and of other components that move through ... More
The core structure of AGN: perils of adaptive optics artifactsOct 16 1998Oct 22 1998As part of a project to map nearby Seyfert galaxies in the near-IR with adaptive optics, we present high spatial resolution, near-IR images in J,H, and K of the nuclei of NGC 3227 and NGC 2992, obtained with the Adaptive Optics Bonnette (AOB) on CFHT. ... More
A unified, mechanistic framework for developmental and evolutionary changeSep 07 2018The two most fundamental processes describing change in biology -development and evolution- occur over drastically different timescales, difficult to reconcile within a unified framework. Development involves a temporal sequence of cell states controlled ... More
Groupoidification Made EasyDec 30 2008Groupoidification is a form of categorification in which vector spaces are replaced by groupoids, and linear operators are replaced by spans of groupoids. We introduce this idea with a detailed exposition of 'degroupoidification': a systematic process ... More
Single Transit Candidates from K2: Detection and Period EstimationDec 11 2015Photometric surveys such as Kepler have the precision to identify exoplanet and eclipsing binary candidates from only a single transit. K2, with its 75d campaign duration, is ideally suited to detect significant numbers of single-eclipsing objects. Here ... More
The X-ray Jet of 3C 120: Evidence for a Non-standard Synchrotron SpectrumJul 16 2004We report on archival data from the Chandra X-ray Observatory for the radio jet of 3C120. We consider the emission process responsible for the X-rays from 4 knots using spectra constructed from radio, optical, and X-ray intensities. While a simple synchrotron ... More
Wide binaries in ultra-faint galaxies: a window onto dark matter on the smallest scalesMay 30 2016We carry out controlled $N$-body simulations that follow the dynamical evolution of binary stars in the dark matter (DM) haloes of ultra-faint dwarf spheroidals (dSphs). We find that wide binaries with semi-major axes $a\gtrsim a_t$ tend to be quickly ... 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
Fourier Transform Model for All-Order PMD Compensation based on a Coupled-Mode Equation Solution using the First Born ApproximationJul 03 2002We present a Fourier transform methodology for all-order polarization mode dispersion (PMD) analysis, based on the first Born approximation to the coupled-mode equation solution. Our method predicts wavelength-dependent PMD effects and allows design of ... More
Nanoarcsecond single-dish imaging of the Vela pulsarJan 21 2000We have measured the properties of the diffractive scintillation toward the Vela pulsar under the extremely strong scattering conditions encountered at 660 MHz. We obtain a decorrelation bandwidth of $\nu_d = 244 \pm 4$ Hz and diffractive decorrelation ... More
Higher-Dimensional Algebra VII: GroupoidificationAug 29 2009Oct 21 2010Groupoidification is a form of categorification in which vector spaces are replaced by groupoids, and linear operators are replaced by spans of groupoids. We introduce this idea with a detailed exposition of "degroupoidification": a systematic process ... More
Spherical Jeans analysis for dark matter indirect detection in dwarf spheroidal galaxies - Impact of physical parameters and triaxialityJul 29 2014Nov 14 2014Dwarf spheroidal (dSph) galaxies are among the most promising targets for the indirect detection of dark matter (DM) from annihilation and/or decay products. Empirical estimates of their DM content - and hence the magnitudes of expected signals - rely ... More
Optimizing Dialogue Management with Reinforcement Learning: Experiments with the NJFun SystemJun 03 2011Designing the dialogue policy of a spoken dialogue system involves many nontrivial choices. This paper presents a reinforcement learning approach for automatically optimizing a dialogue policy, which addresses the technical challenges in applying reinforcement ... More
Accelerating the Uzawa AlgorithmOct 14 2015May 23 2016The Uzawa algorithm is an iterative method for the solution of saddle-point problems, which arise in many applications, including fluid dynamics. Viewing the Uzawa algorithm as a fixed- point iteration, we explore the use of Anderson acceleration (also ... More
In situ measurement of MWA primary beam variation using ORBCOMMAug 14 2018We provide the first in situ measurements of antenna element (tile) beam shapes of the Murchison Widefield Array (MWA), a low radio-frequency interferometer and an SKA precursor. Most current MWA processing pipelines use an assumed beam shape, errors ... More