Results for "S. E. Gibson"

total 225860took 0.15s
Additive Self Helicity as a Kink Mode ThresholdSep 27 2009In this paper we propose that additive self helicity, introduced by Longcope and Malanushenko (2008), plays a role in the kink instability for complex equilibria, similar to twist helicity for thin flux tubes (Hood and Priest (1979), Berger and Field ... More
Three-body structure of the $nnΛ$ system with $ΛN-ΣN$ couplingMay 09 2014The structure of the three-body $nn\Lambda$ system, which has been observed recently by the HypHI collaboration, is investigated taking $\Lambda N-\Sigma N$ coupling explicitly into account. The $YN$ and $NN$ interactions employed in this work reproduce ... More
Coronal cavities: observations and implications for the magnetic environment of prominencesFeb 07 2017Dark and elliptical, coronal cavities yield important clues to the magnetic structures that cradle prominences, and to the forces that ultimately lead to their eruption. We review observational analyses of cavity morphology, thermal properties (density ... More
Sign Stability via Root Locus AnalysisDec 18 2015With the rise of network science old topics in ecology and economics are resurfacing. One such topic is structural stability (often referred to as qualitative stability or sign stability). A system is deemed structurally stable if the system remains stable ... More
Diagnostics of Coronal Magnetic Fields Through the Hanle Effect in UV and IR LinesJun 27 2016The plasma thermodynamics in the solar upper atmosphere, particularly in the corona, are dominated by the magnetic field, which controls the flow and dissipation of energy. The relative lack of knowledge of the coronal vector magnetic field is a major ... More
Partially-erupting prominences: a comparison between observations and model-predicted observablesFeb 07 2009AIM: To investigate several partially-erupting prominences to study their relationship with other CME-associated phenomena and to compare these observations with observables predicted by a model of partially-expelled flux ropes (Gibson & Fan, 2006a, b). ... More
Numerical Methods for Linear Diffusion Equations in the Presence of an InterfaceOct 30 2013We consider numerical methods for linear parabolic equations in one spatial dimension having piecewise constant diffusion coefficients defined by a one parameter family of interface conditions at the discontinuity. We construct immersed interface finite ... More
The Spectroscopic Age of 47 TucJun 04 1999High signal-to-noise integrated spectra of the metal-rich globular cluster 47 Tuc, spanning the H-gamma(HR) and Fe4668 line indices, have been obtained. The combination of these indices has been suggested (Jones & Worthey 1995, ApJ, 446, L31) as the best ... More
Mapping Hydrogen in the Galaxy, Galactic Halo, and Local Group with ALFA: The GALFA-HI Survey Starting with TOGSApr 30 2008Radio observations of gas in the Milky Way and Local Group are vital for understanding how galaxies function as systems. The unique sensitivity of Arecibo's 305m dish, coupled with the 7-beam Arecibo L-Band Feed Array (ALFA), provides an unparalleled ... More
Characterization and Status of a Terahertz TelescopeJun 11 2004The Receiver Lab Telescope (RLT) is a ground-based terahertz observatory, located at an altitude of 5525 m on Cerro Sairecabur, Chile. The RLT has been in operation since late 2002, producing the first well-calibrated astronomical data from the ground ... More
Polarimetric Properties of Flux-Ropes and Sheared Arcades in Coronal Prominence CavitiesApr 29 2013The coronal magnetic field is the primary driver of solar dynamic events. Linear and circular polarization signals of certain infrared coronal emission lines contain information about the magnetic field, and to access this information, either a forward ... More
Projection Operator in Adaptive SystemsDec 19 2011Oct 16 2012The projection algorithm is frequently used in adaptive control and this note presents a detailed analysis of its properties.
ROAM: a Radial-basis-function Optimization Approximation Method for diagnosing the three-dimensional coronal magnetic fieldJul 12 2016The Coronal Multichannel Polarimeter (CoMP) routinely performs coronal polarimetric measurements using the Fe XIII 10747 $\AA$ and 10798 $\AA$ lines, which are sensitive to the coronal magnetic field. However, inverting such polarimetric measurements ... More
The Magnetic Structure of Solar Prominence Cavities: New Observational Signature Revealed by Coronal MagnetometryApr 27 2013The Coronal Multi-channel Polarimeter (CoMP) obtains daily full-Sun above-the-limb coronal observations in linear polarization, allowing for the first time a diagnostic of the coronal magnetic field direction in quiescent prominence cavities. We find ... More
Data-Optimized Coronal Field Model: I. Proof of ConceptApr 12 2019Deriving the strength and direction of the three-dimensional (3D) magnetic field in the solar atmosphere is fundamental for understanding its dynamics. Volume information on the magnetic field mostly relies on coupling 3D reconstruction methods with photospheric ... More
Flux line lattice structure and behaviour in anti-phase boundary free vicinal YBa2Cu3O7-d thin filmsJan 27 2003Field angle dependent critical current, magneto-optical microscopy, and high resolution electron microscopy studies have been performed on YBa2Cu3O7-d thin films grown on mis-cut substrates. High resolution electron microscopy images show that the films ... More
The Disruption and Fueling of M33Dec 12 2008Dec 23 2009The disruption of the M33 galaxy is evident from its extended gaseous structure. We present new data from the Galactic Arecibo L-Band Feed Array HI (GALFA-HI) Survey that show the full extent and detailed spatial and kinematic structure of M33's neutral ... More
The First Results from the Parkes Multibeam High-Velocity Cloud SurveyFeb 14 1999With the onset of the HI Parkes All-Sky Survey, a new view of the high-velocity cloud (HVC) distribution in the southern sky is being revealed. The dense spatial sampling and unbiased coverage of HIPASS gives it multiple advantages over previous surveys ... More
Goodness in the Axis of EvilFeb 21 2008Jun 11 2008An unexpected alignment of 2-4-8-16 cosmic microwave background spherical harmonic directions with the direction of a surprisingly large WMAP temperature minimum, a large radio galaxy void, and an unexpected alignment and handedness of galaxy spins have ... More
Interpretation of the Stephan Quintet Galaxy Cluster using Hydro-Gravitational TheoryApr 06 2003Stephan's Quintet (SQ) is a compact group of galaxies that has been well studied since its discovery in 1877 but is mysterious using cold dark matter hierarchical clustering cosmology (CDMHCC). Anomalous red shifts z = (0.0027,0.019, 0.022, 0.022, 0.022) ... More
H_alpha Emission from High-Velocity Clouds and their DistancesJul 29 2003We present deep Halpha spectroscopy towards several high-velocity clouds (HVCs) which vary in structure from compact (CHVCs) to the Magellanic Stream. The clouds range from being bright (~640 mR) to having upper limits on the order of 30 to 70 mR. The ... More
Beyond sunspots: Studies using the McIntosh Archive of global solar magnetic field patternsAug 24 2018In 1964 (Solar Cycle 20; SC 20), Patrick McIntosh began creating hand-drawn synoptic maps of solar magnetic features, based on H$\alpha$ images. These synoptic maps were unique in that they traced magnetic polarity inversion lines, and connected widely ... More
Turbulent formation of protogalaxies at the plasma to gas transitionMay 08 2011May 18 2011The standard model of gravitational structure formation is based on the Jeans 1902 acoustic theory, neglecting crucial effects of viscosity, turbulence and diffusion. A Jeans length scale L_J emerges that exceeds the scale of causal connection ct during ... More
Primordial Planet FormationDec 26 2010Recent spacecraft observations exploring solar system properties impact standard paradigms of the formation of stars, planets and comets. We stress the unexpected cloud of microscopic dust resulting from the DEEP IMPACT mission, and the existence of molten ... More
Clumps of hydrogenous planetoids as the dark matter of galaxiesAug 30 1999Jun 03 2000Nonlinear gravitational condensation theory and quasar-microlensing observations lead to the conclusion that the baryonic mass of most galaxies is dominated by dense clumps of hydrogenous planetoids. Star microlensing collaborations fail to detect planetoids ... More
Quasar-microlensing versus star-microlensing evidence of small-planetary-mass objects as the dominant inner-halo galactic dark matterApr 26 1999Apr 26 2000We examine recent results of two kinds of microlensing experiments intended to detect galactic dark matter objects, and we suggest that the lack of short period star-microlensing events observed for stars near the Galaxy does not preclude either the ``rogue ... More
Formation of Planets by Hydrogravitational DynamicsDec 26 2010From hydro-gravitational cosmology, hydrogen-helium gas planets fragmented at the plasma to gas transition 300,000 years after the big bang in million-star-mass clumps. Stars may form in the clumps by mergers of the planets to make globular star clusters. ... More
Hydro-Gravitational-Dynamics of Planets and Dark EnergyAug 24 2008Self-gravitational fluid mechanical methods termed hydro-gravitational-dynamics (HGD) predict plasma fragmentation 0.03 Myr after the turbulent big bang to form protosuperclustervoids, turbulent protosuperclusters, and protogalaxies at the 0.3 Myr transition ... More
Theory and observations of galactic dark matterApr 26 1999Sir James Jeans's (1902 and 1929) linear, acoustic, theory of gravitational instability gives vast errors for the structure formation of the early universe. Gibson's (1996) nonlinear theory shows that nonacoustic density extrema produced by turbulence ... More
Turbulent formation of protogalaxies at the end of the plasma epoch: theory and observationsSep 12 2008Sep 16 2008The standard model of gravitational structure formation is based on the Jeans 1902 acoustic theory, neglecting nonlinear instabilities controlled by viscosity, turbulence and diffusion. Because the Jeans scale L_J for the hot primordial plasma is always ... More
Interpretation of the Helix Planetary Nebula using Hydro-Gravitational-Dynamics: Planets and Dark EnergyJan 16 2007Nov 02 2007Hubble Space Telescope images of the Helix Planetary Nebula are interpreted using the hydro-gravitational-dynamics theory (HGD) of Gibson 1996-2006. HGD claims that baryonic-dark-matter (BDM) dominates the halo masses of galaxies (Schild 1996) as Jovian ... More
Interpretation of the Tadpole VV29 Merging Galaxy System using Hydro-Gravitational TheoryOct 26 2002May 03 2003Hubble Space Telescope (HST/ACS) images of the galaxy merger Tadpole are interpreted using the hydro-gravitational theory of Gibson 1996-2000 (HGT) that predicts galaxy masses within about 100 kpc are dominated by dark halos of planetary mass primordial-fog-particles ... More
Interpretation of the Stephan Quintet Galaxy Cluster using Hydro-Gravitational-Dynamics: Viscosity and FragmentationOct 29 2007Oct 31 2007Stephan's Quintet (SQ) is a compact group of galaxies that has been well studied since its discovery in 1877 but is mysterious using cold dark matter hierarchical clustering cosmology (CDMHCC). Anomalous red shifts $z = (0.0027,0.019, 0.022, 0.022, 0.022)$ ... More
Evolution of proto-galaxy-clusters to their present form: theory and observationsSep 12 2008Sep 14 2008From hydro-gravitational-dynamics theory HGD, gravitational structure formation begins 30,000 years after the turbulent big bang by fragmentation into super-cluster-voids and super-clusters. Proto-galaxies in linear and spiral clusters are the smallest ... More
Spatially localized solutions of shear flowsApr 23 2013We present several new spatially localized equilibrium and traveling-wave solutions of plane Couette and channel flows. The solutions exhibit strikingly concentrated regions of vorticity that are flanked on either side by high-speed streaks. For several ... More
Non-invasive, near-field terahertz imaging of hidden objects using a single pixel detectorSep 10 2015Feb 18 2016Terahertz (THz) imaging has the ability to see through otherwise opaque materials. However, due to the long wavelengths of THz radiation ({\lambda}=300{\mu}m at 1THz), far-field THz imaging techniques are heavily outperformed by optical imaging in regards ... More
The Galactic Nature of High Velocity Cloud Complex WBJan 06 2006We have detected absorption lines from the High Velocity Cloud Complex WB in the spectrum of the star HE1048+0231. This detection sets an upper distance limit to the cloud of 8.8^{+2.3}_{-1.3} kpc. Non-detection (at >4 sigma confidence) in the star HE1138-1303 ... More
The $π^+$--emission puzzle in $^4_Λ$He decayNov 26 1997We re-examine the puzzling $\pi^+$ emission from the weak decay of $^4_\Lambda$He and propose an explanation in terms of a three-body decay of the virtual $\Sigma^+$. Such a resolution of the $\pi^+$ decay puzzle is consistent with the calculated $\Sigma^+$ ... More
Is Dark Energy Falsifiable?Dec 13 2011Is the accelerating expansion of the Universe true, inferred through observations of distant supernovae, and is the implied existence of an enormous amount of anti-gravitational dark energy material driving the accelerating expansion of the universe also ... More
Evolution of proto-galaxy-clusters to their present form: theory and observationsApr 12 2010From hydro-gravitational-dynamics theory HGD, gravitational structure formation begins 30,000 years (10^12 s) after the turbulent big bang by viscous-gravitational fragmentation into super-cluster-voids and 10^46 kg proto-galaxy-super-clusters. Linear ... More
Planets and Dark EnergyMar 30 2008Self gravitational fluid mechanical methods termed hydro-gravitational-dynamics (HGD) predict plasma fragmentation 0.03 Myr after the turbulent big bang to form protosuperclustervoids, turbulent protosuperclusters, and protogalaxies at the 0.3 Myr transition ... More
Interpretation of the Helix Planetary Nebula using Hydro-Gravitational TheoryJun 23 2003Jun 25 2003Wide angle Hubble Space Telescope (HST/ACS) images of the Helix Planetary Nebula (NGC 7293) are interpreted using the hydro-gravitational theory (HGT) of Gibson 1996-2000 that predicts the baryonic dark matter and interstellar medium (ISM) consists of ... More
Robust and Scalable Models of Microbiome DynamicsMay 11 2018Jun 08 2018Microbes are everywhere, including in and on our bodies, and have been shown to play key roles in a variety of prevalent human diseases. Consequently, there has been intense interest in the design of bacteriotherapies or "bugs as drugs," which are communities ... More
Long-term X-ray stability and UV variability of the ionized absorption in NGC 3783Oct 16 2014We present the results of recent Chandra High-Energy Transmission Grating Spectrometer and Hubble Space Telescope Cosmic Origins Spectrograph observations of the nearby Seyfert 1 galaxy NGC 3783 which shows a strong, non-varying X-ray warm absorber and ... More
A highly efficient two level diamond based single photon sourceMar 23 2009An unexplored diamond defect centre which is found to emit stable single photons at a measured rate of 1.6 MHz at room temperature is reported. The novel centre, identified in chemical vapour deposition grown diamond crystals, exhibits a sharp zero phonon ... More
Nano-manipulation of diamond-based single photon sourcesMay 18 2009The ability to manipulate nano-particles at the nano-scale is critical for the development of active quantum systems. This paper presents a new technique to manipulate diamond nano-crystals at the nano-scale using a scanning electron microscope, nano-manipulator ... More
The structure of test functions that determine weighted composition operatorsApr 09 2012In the context of analytic functions on the open unit disk, a weighted composition operator is simply a composition operator followed by a multiplication operator. The class of weighted composition operators has an important place in the theory of Banach ... More
Experimental results of the laserwire emittance scanner for LINAC4 at CERNNov 18 2015Within the framework of the LHC Injector Upgrade (LIU), the new LINAC4 is currently being commissioned to replace the existing LINAC2 proton source at CERN. After the expected completion at the end of 2016, the LINAC4 will accelerate H- ions to 160 MeV. ... More
Ground-based detection of thermal emission from the exoplanet WASP-19bFeb 09 2010Mar 05 2010We present an occultation of the newly discovered hot Jupiter system WASP-19, observed with the HAWK-I instrument on the VLT, in order to measure thermal emission from the planet's dayside at ~2 um. The light curve was analysed using a Markov-Chain Monte-Carlo ... More
Detection of H2O and evidence for TiO/VO in an ultra hot exoplanet atmosphereApr 08 2016We present a primary transit observation for the ultra hot (Teq~2400K) gas giant expolanet WASP-121b, made using the Hubble Space Telescope Wide Field Camera 3 in spectroscopic mode across the 1.12-1.64 micron wavelength range. The 1.4 micron water absorption ... More
Demonstration of a laserwire emittance scanner for the CERN LINAC4 H- BeamAug 24 2015Nov 17 2015A non-invasive, compact laserwire system has been developed to measure the transverse emittance of an H- beam and has been demonstrated at the new LINAC4 injector for the LHC at CERN. Light from a low power, pulsed laser source is conveyed via fibre to ... More
A lower mass for the exoplanet WASP-21bJun 10 2011We present high precision transit observations of the exoplanet WASP-21b, obtained with the RISE instrument mounted on 2.0m Liverpool Telescope. A transit model is fitted, coupled with an MCMC routine to derive accurate system parameters. The two new ... More
The spin-orbit alignment of the transiting exoplanet WASP-3b from Rossiter-McLaughlin observationsDec 18 2009Jun 28 2010We present an observation of the Rossiter-McLaughlin effect for the planetary system WASP-3. Radial velocity measurements were made during transit using the SOPHIE spectrograph at the 1.93m telescope at Haute-Provence Observatory. The shape of the effect ... More
Primordial planets, comets and moons foster life in the cosmosAug 22 2010A key result of hydrogravitational dynamics cosmology relevant to astrobiology is the early formation of vast numbers of hot primordial-gas planets in million-solar-mass clumps as the dark matter of galaxies and the hosts of first life. Photon viscous ... More
General properties of the pion production reaction in nuclear matterJan 16 2004The pion production reaction $\pi^+ \to \pi^+\pi^{\pm}$ on $^{45}Sc$ was studied at incident pion energies of $T_{\pi^{+}}$ = 240, 260, 280, 300, and 320 MeV. The experiment was performed using the $M11$ pion-channel at TRIUMF, and multiparticle events, ... More
The pi -> pi pi process in nuclei and the restoration of chiral symmetryAug 24 2005The results of an extensive campaign of measurements of the pi -> pi pi process in the nucleon and nuclei at intermediate energies are presented. The measurements were motivated by the study of strong pi pi correlations in nuclei. The analysis relies ... More
Hydrodynamics of structure formation in the early UniverseSep 14 2008Sep 16 2009Theory and observations reveal fatal flaws in the standard LambdaCDM model. The cold dark matter hierarchical clustering paradigm predicts a gradual bottom-up growth of gravitational structures assuming linear, collisionless, ideal flows and unrealistic ... More
Origins of the Ambient Solar Wind: Implications for Space WeatherAug 23 2017The Sun's outer atmosphere is heated to temperatures of millions of degrees, and solar plasma flows out into interplanetary space at supersonic speeds. This paper reviews our current understanding of these interrelated problems: coronal heating and the ... More
The Origin of Life from Primordial PlanetsApr 04 2010Jul 06 2010The origin of life and the origin of the universe are among the most important problems of science and they might be inextricably linked. Hydro-gravitational-dynamics (HGD) cosmology predicts hydrogen-helium gas planets in clumps as the dark matter of ... More
On Adaptive Control with Closed-loop Reference Models: Transients, Oscillations, and PeakingApr 26 2013Aug 08 2013One of the main features of adaptive systems is an oscillatory convergence that exacerbates with the speed of adaptation. Recently it has been shown that Closed-loop Reference Models (CRMs) can result in improved transient performance over their open-loop ... More
Do micro brown dwarf detections explain the galactic dark matter?Nov 10 2010Context: The baryonic dark matter dominating the structures of galaxies is widely considered as mysterious, but hints for it have been in fact detected in several astronomical observations at optical, infrared, and radio wavelengths. We call attention ... More
Why are so many primitive stars observed in the Galaxy halo?Jun 01 2012Small values of lithium observed in a small, primitive, Galaxy-Halo star SDSS J102915 + 172927 cannot be explained using the standard cold dark matter CDM theory of star formation, but are easily understood using the Gibson/Schild 1996 hydrogravitationaldynamics ... More
New HI Features of the Magellanic SystemNov 09 1998The first results from the HI Parkes All-Sky Survey (HIPASS) provide a spectacular view of the global HI distribution in the vicinity of the Magellanic Clouds and the southern Milky Way. A 2400 square degree mosaic around the South Celestial Pole (SCP) ... More
Primordial Planets Explain Interstellar Dust, the Formation of Life; and Falsify Dark EnergyDec 15 2011Hydrogravitional-dynamics (HGD) cosmology of Gibson/Schild 1996 predicts proto-globular-star-cluster PGC clumps of Earth-mass planets fragmented from plasma at ~0.3 Myr. Protogalaxies retained the ~0.03 Myr baryonic density existing at the time of the ... More
First life in primordial-planet oceans: the biological big bangSep 09 2010Sep 19 2010A scenario is presented for the formation of first life in the universe based on hydro-gravitational-dynamics (HGD) cosmology. From HGD, the dark matter of galaxies is H-He gas dominated planets (primordial-fog-particle PFPs) in million solar mass clumps ... More
Gravitational hydrodynamics of large scale structure formationJun 27 2009Jul 02 2009The gravitational hydrodynamics of the primordial plasma with neutrino hot dark matter is considered as a challenge to the bottom-up cold dark matter paradigm. Viscosity and turbulence induce a top-down fragmentation scenario before and at decoupling. ... More
Adaptive Output Feedback based on Closed-loop Reference ModelsOct 07 2014This note presents the design and analysis of an adaptive controller for a class of linear plants in the presence of output feedback. This controller makes use of a closed-loop reference model as an observer, and guarantees global stability and asymptotic ... More
Tuning the electronic and the crystalline structure of LaBi by pressureJul 13 2016Extreme magnetoresistance (XMR) in topological semimetals is a recent discovery which attracts attention due to its robust appearance in a growing number of materials. To search for a relation between XMR and superconductivity, we study the effect of ... More
Closed-loop Reference Models for Output-Feedback Adaptive SystemsOct 31 2012Nov 28 2012Closed-loop reference models have recently been proposed for states accessible adaptive systems. They have been shown to have improved transient response over their open loop counter parts. The results in the states accessible case are extended to single ... More
Adaptive Systems with Closed-loop Reference Models: Stability, Robustness and Transient PerformanceJan 23 2012Oct 30 2012This paper explores the properties of adaptive systems with closed-loop reference models. Using additional design freedom available in closed-loop reference models, we design new adaptive controllers that are (a) stable, and (b) have improved transient ... More
Gravitational hydrodynamics vs observations of voids, Jeans clusters and MACHO dark matterMar 01 2010Gravitational hydrodynamics acknowledges that hydrodynamics is essentially nonlinear and viscous. In the plasma, at $z=5100$, the viscous length enters the horizon and causes fragmentation into plasma clumps surrounded by voids. The latter have expanded ... More
The Mass Function of Primordial Rogue Planet MACHOs in quasar nanolensingDec 12 2012The recent Sumi et al (2010, 2011) detection of free roaming planet mass MACHOs in cosmologically significant numbers recalls their original detection in quasar microlening studies (Schild 1996, Colley and Schild 2003). We consider the microlensing signature ... More
$Ξ^{-} d\to nΛΛ$ and the $ΛΛ$ final state interactionDec 16 1997The reaction $\Xi^-d\to n\Lambda\Lambda$ is studied within the framework of the Faddeev equations as a possible tool to gain insight into the final state $\Lambda$--$\Lambda$ interaction. The neutron differential energy spectrum gives a final state interaction ... More
A map of OMC-1 in CO 9-8May 26 2004Sep 06 2004The distribution of 12C16O J=9-8 (1.037 THz) emission has been mapped in OMC-1 at 35 points with 84" resolution. This is the first map of this source in this transition and only the second velocity-resolved ground-based observation of a line in the terahertz ... More
Non-uniform carrier density in Cd$_3$As$_2$ evidenced by optical spectroscopyDec 08 2017Mar 11 2018We report the detailed optical properties of Cd$_3$As$_2$ crystals in a wide parameter space: temperature, magnetic field, carrier concentration and crystal orientation. We investigate high-quality crystals synthesized by three different techniques. In ... More
The [alpha/Fe] ratios of very metal-poor stars within the IGIMF theoryOct 16 2013The aim of this paper is to quantify the amplitude of the predicted plateau in [alpha/Fe] ratios associated with the most metal-poor stars of a galaxy. We assume that the initial mass function in galaxies is steeper if the star formation rate (SFR) is ... More
Galactic Cannibalism: the Origin of the Magellanic StreamJan 24 2002We are in a privileged location in the Universe which allows us to observe galactic interactions from close range -- the merger of our two nearest dwarf satellite galaxies, the LMC and SMC. It is important to understand the local merger process before ... More
Gas and Metal Distributions within Simulated Disk GalaxiesApr 06 2012We highlight two research strands related to our ongoing chemodynamical Galactic Archaeology efforts: (i) the spatio-temporal infall rate of gas onto the disk, drawing analogies with the infall behaviour imposed by classical galactic chemical evolution ... More
The $λΛ$ interaction and the reaction $Ξ^- + d \to n + Λ+ Λ$Sep 02 1997The $\Lambda\Lambda$ interaction resulting from the SU(3) rotation of the S-wave component of the Nijmegen OBE potential $D$ is used to calculate the binding energy of $^{ 6}_{\Lambda\Lambda}$He as a $\Lambda\Lambda\alpha$ three-body system, and the neutron ... More
Numerical study of critical properties and hidden orders in dimerized spin laddersSep 27 2010Mar 29 2011Dimerized antiferromagnetic spin-1/2 ladders are known to exhibit a quantum critical phase transition in the ground state, the existence or absence of which is dependent on the dimerization pattern of the ladder. The gapped phases cannot be distinguished ... More
Observationally-Motivated Analysis of Simulated GalaxiesFeb 02 2015The spatial and temporal relationships between stellar age, kinematics, and chemistry are a fundamental tool for uncovering the physics driving galaxy formation and evolution. Observationally, these trends are derived using carefully selected samples ... More
Superconducting Properties of BaBi$_{3}$Jun 11 2014We report the superconducting properties of single crystals of the intermetallic perovskite-related compound BaBi$_{3}$. The superconducting transition temperature ($T_{c}=5.82$~K) was obtained from heat capacity measurements. Using the measured values ... More
Stellar abundance gradients in galactic disks. I. Method and spectral line gradientsJan 17 2005We describe the technique of absorption line imaging of galaxy disks using the Taurus Tunable Filter on the Anglo-Australian Telescope and demonstrate its sensitivity to the behaviour of spectral features associated with Mg and Fe. Radial profiles of ... More
$^{6}_{ΛΛ}$He as a $ΛΛ$ interaction constraintSep 04 1997The Nijmegen OBE potential D is SU(3) rotated to model the strangeness -2 sector of the baryon-baryon force. Soft core repulsion is introduced to regularize the singular nature of the OBE functions. The strength of the $^1$S$_0$ $t=0$ interaction is adjusted ... More
Action-gradient-minimizing pseudo-orbits and almost-invariant toriApr 29 2011Transport in near-integrable, but partially chaotic, $1 1/2$ degree-of-freedom Hamiltonian systems is blocked by invariant tori and is reduced at \emph{almost}-invariant tori, both associated with the invariant tori of a neighboring integrable system. ... More
Unified Theory of Ghost and Quadratic-Flux-Minimizing SurfacesJan 04 2010Aug 02 2011A generalized Hamiltonian definition of ghost surfaces (surfaces defined by an action-gradient flow) is given and specialized to the usual Lagrangian definition. Numerical calculations show uncorrected quadratic-flux-minimizing (QFMin) and Lagrangian ... More
Making FORS2 fit for exoplanet observations (again)Feb 11 2015For about three years, it was known that precision spectrophotometry with FORS2 suffered from systematic errors that made quantitative observations of planetary transits impossible. We identified the Longitudinal Atmospheric Dispersion Compensator (LADC) ... More
On Chip Manipulation of Single Photons from a Diamond DefectApr 15 2013Apr 19 2013Operating reconfigurable quantum circuits with single photon sources is a key goal of photonic quantum information science and technology. We use an integrated waveguide device comprising of directional couplers and a reconfigurable thermal phase controller ... More
NICMOS Observations of Extragalactic Cepheids. I. Photometry Database and a Test of the Standard Extinction LawFeb 07 2001We present the results of near-infrared observations of extragalactic Cepheids made with the Near Infrared Camera and Multi-Object Spectrometer on board the Hubble Space Telescope. The variables are located in the galaxies IC 1613, IC 4182, M 31, M 81, ... More
A statistical modelling framework for mapping malaria seasonalityJan 30 2019Many malaria-endemic areas experience seasonal fluctuations in cases because the mosquito vector's life cycle is dependent on the environment. While most existing maps of malaria seasonality use fixed thresholds of rainfall, temperature and vegetation ... More
Observing the metal-poor solar neighbourhood: a comparison of galactic chemical evolution predictionsMay 10 2017Atmospheric parameters and chemical compositions for ten stars with metallicities in the region of -2.2< [Fe/H] <-0.6 were precisely determined using high resolution, high signal to noise, spectra. For each star the abundances, for 14 to 27 elements, ... More
IAU commission 10 "Solar Activity": Legacy report and triennial report for 2012-2015Oct 12 2015After more than half a century of community support related to the science of "solar activity'', IAU's Commission 10 was formally discontinued in 2015, to be succeeded by C.E2 with the same area of responsibility. On this occasion, we look back at the ... More
Path to perfect photon entanglement with a quantum dotOct 30 2017Realizing perfect two-photon entanglement from quantum dots has been a long-standing scientific challenge. It is generally thought that the nuclear spins limit the entanglement fidelity through spin flip dephasing processes. However, this assumption lacks ... More
Thin disc, Thick Disc and Halo in a Simulated GalaxyJun 04 2012Within a cosmological hydrodynamical simulation, we form a disc galaxy with sub- components which can be assigned to a thin stellar disc, thick disk, and a low mass stellar halo via a chemical decomposition. The thin and thick disc populations so selected ... More
Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random WalkApr 02 2010Aug 21 2010We model the time variability of ~9,000 spectroscopically confirmed quasars in SDSS Stripe 82 as a damped random walk. Using 2.7 million photometric measurements collected over 10 years, we confirm the results of Kelly et al. (2009) and Koz{\l}owski et ... More
A Global View of Molecule-Forming Clouds in the GalaxyOct 22 2015We have mapped cold atomic gas in 21cm line HI self-absorption (HISA) at arcminute resolution over more than 90% of the Milky Way's disk. To probe the formation of H2 clouds, we have compared our HISA distribution with CO J=1-0 line emission. Few HISA ... More
Globular Cluster and Galaxy Formation: M31, the Milky Way and Implications for Globular Cluster Systems of Spiral GalaxiesJun 24 2004The globular cluster (GC) systems of the Milky Way and of our neighboring spiral galaxy, M31, comprise 2 distinct entities, differing in 3 respects. 1. M31 has young GCs, ages from ~100 Myr to 5 Gyr old, as well as old globular clusters. No such young ... More
Thick disk kinematics from RAVE and the solar motionSep 03 2012Radial velocity surveys such as the Radial Velocity Experiment (RAVE) provide us with measurements of hundreds of thousands of nearby stars most of which belong to the Galactic thin, thick disk or halo. Ideally, to study the Galactic disks (both thin ... More
Accelerated Learning in the Presence of Time Varying Features with Applications to Machine Learning and Adaptive ControlMar 12 2019Features in machine learning problems are often time varying and may be related to outputs in an algebraic or dynamical manner. The dynamic nature of these machine learning problems renders current accelerated gradient descent methods unstable or weakens ... More
Provably Correct Learning Algorithms in the Presence of Time-Varying Features Using a Variational PerspectiveMar 12 2019Apr 29 2019Features in machine learning problems are often time-varying and may be related to outputs in an algebraic or dynamical manner. The dynamic nature of these machine learning problems renders current accelerated gradient descent methods unstable or weakens ... More