Results for "Karen M. Kuntz"

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Many-body Green's function theory for thin ferromagnetic films: exact treatment of the single-ion anisotropyJan 08 2002A theory for the magnetization of ferromagnetic films is formulated within the framework of many-body Green's funtion theory which considers all components of the magnetization. The model Hamiltonian includes a Heisenberg term, an external field, a second- ... More
Spatial and temporal characterization of a Bessel beam produced using a conical mirrorDec 15 2008We experimentally analyze a Bessel beam produced with a conical mirror, paying particular attention to its superluminal and diffraction-free properties. We spatially characterized the beam in the radial and on-axis dimensions, and verified that the central ... More
Higgs Starobinsky InflationMay 07 2016In this paper we point out that Starobinky inflation could be induced by quantum effects due to a large non-minimal coupling of the Higgs boson to the Ricci scalar. The Higgs Starobinsky mechanism provides a solution to issues attached to large Higgs ... More
Fragmentation Phase Transition in Atomic Clusters II - Coulomb Explosion of Metal Clusters -Feb 20 1997We discuss the role and the treatment of polarization effects in many-body systems of charged conducting clusters and apply this to the statistical fragmentation of Na-clusters. We see a first order microcanonical phase transition in the fragmentation ... More
Irrelevant Exceptional Divisors for Curves on a Smooth SurfaceNov 24 2006Aug 28 2007Given a singular curve on a smooth surface, we determine which exceptional divisors on the minimal resolution of that curve contribute toward its jumping numbers.
Magnetostrictive Fe73Ga27 nanocontacts for low field conductance switchingJun 06 2016The electrical conductance G of magnetostrictive nanocontacts made from Galfenol Fe73Ga27 can be reproducibly switched between on and off states in a low magnetic field of 20 to 30 mT at 10 K. The switching behavior is in agreement with the magnetic field ... More
Many-body Green's function theory for thin ferromagnetic anisotropic Heisenberg films: treatment of the exchange anisotropyMar 19 2003The many-body Green's function theory developed in our previous work for treating the reorientation of the magnetization of thin ferromagnetic films is extended to include the exchange anisotropy. This leads to additional momentum dependencies which require ... More
Characterization and valuation of uncertainty of calibrated parameters in stochastic decision modelsJun 11 2019We evaluated the implications of different approaches to characterize uncertainty of calibrated parameters of stochastic decision models (DMs) in the quantified value of such uncertainty in decision making. We used a microsimulation DM of colorectal cancer ... More
First-principles study of symmetry lowering in relaxed BaTiO3/SrTiO3 superlatticesNov 24 2004The crystal structure and local spontaneous polarization of (BaTiO3)m/(SrTiO3)n superlattices is calculated using a first-principles density functional theory method. The in-plane lattice constant is 1% larger than the SrTiO3 substrate to imitate the ... More
Imprints of Quantum Gravity in the Cosmic Microwave BackgroundMar 04 2019It has been shown that the spectrum of quantum gravity contains at least two new modes in addition to the massless graviton: a massive spin-0 and a massive spin-2. We calculate their power spectrum during inflation and we argue that they could leave an ... More
Non-Minimal Coupling of the Higgs Boson to Curvature in an Inflationary UniverseJan 09 2017In the absence of new physics around $10^{10}$ GeV, the electroweak vacuum is at best metastable. This represents a major challenge for high scale inflationary models as, during the early rapid expansion of the universe, it seems difficult to understand ... More
Small-time fluctuations for sub-Riemannian diffusion loopsJun 01 2016Aug 27 2018We study the small-time fluctuations for diffusion processes which are conditioned by their initial and final positions, under the assumptions that the diffusivity has a sub-Riemannian structure and that the drift vector field lies in the span of the ... More
Gravitational Waves in Effective Quantum GravityJul 10 2016In this short paper we investigate quantum gravitational effects on Einstein's equations using effective field theory techniques. We consider the leading order quantum gravitational correction to the wave equation. Besides the usual massless mode, we ... More
A Hopf algebraic approach to Schur function identitiesNov 19 2015Jun 09 2017Using cocommutativity of the Hopf algebra of symmetric functions, certain skew Schur functions are proved to be equal. Some of these skew Schur function identities are new.
The z=0.54 LoBAL Quasar SDSS J085053.12+445122.5: I. Spectral Synthesis Analysis Reveals a Massive OutflowAug 07 2018We introduce SimBAL, a novel spectral-synthesis procedure that uses large grids of ionic column densities generated by the photoionization code Cloudy and a Bayesian model calibration to forward-model broad absorption line quasar spectra. We used SimBAL ... More
Self-healing Dynamics of Surfactant Coatings on Thin Viscous FilmsSep 13 2013Feb 11 2014We investigate the dynamics of an insoluble surfactant on the surface of a thin viscous fluid spreading inward to fill a surfactant-free region. During the initial stages of surfactant self-healing, Marangoni forces drive an axisymmetric ridge inward ... More
Extraction of Force-Chain Network Architecture in Granular Materials Using Community DetectionAug 17 2014Apr 23 2015Force chains form heterogeneous physical structures that can constrain the mechanical stability and acoustic transmission of granular media. However, despite their relevance for predicting bulk properties of materials, there is no agreement on a quantitative ... More
High refractive index immersion liquid for super-resolution 3D imaging using sapphire-based aNAIL opticsDec 27 2015Apr 20 2016Optically-transparent immersion liquids with refractive index (n ~ 1.77) to match sapphire-based aplanatic numerical aperture increasing lens (aNAIL) are necessary for achieving deep 3D imaging with high spatial resolution. We report that antimony tribromide ... More
Coupled ferro-antiferromagnetic Heisenberg bilayers investigated by many-body Green's function theoryJul 18 2005A theory of coupled ferro- and antiferromagnetic Heisenberg layers is developed within the framework of many-body Green's function theory (GFT) that allows non-collinear magnetic arrangements by introducing sublattice structures. As an example, the coupled ... More
Field-induced magnetic reorientation and effective anisotropy of a ferromagnetic monolayer within spin wave theoryOct 18 1999The reorientation of the magnetization of a ferromagnetic monolayer is calculated with the help of many-body Green's function theory. This allows, in contrast to other spin wave theories, a satisfactory calculation of magnetic properties over the entire ... More
Fluorescent visualization of a spreading surfactantNov 21 2009Mar 25 2010The spreading of surfactants on thin films is an industrially and medically important phenomenon, but the dynamics are highly nonlinear and visualization of the surfactant dynamics has been a long-standing experimental challenge. We perform the first ... More
The Intrinsically X-ray Weak Quasar PHL 1811. I. X-ray Observations and Spectral Energy DistributionNov 10 2006This is the first of two papers reporting observations and analysis of the unusually bright (m_b=14.4), luminous (M_B=-25.5), nearby (z=0.192) narrow-line quasar PHL 1811, focusing on the X-ray properties and the spectral energy distribution. Two Chandra ... More
A Study of Pi Aquarii During a Quasi-normal Star Phase: Refined Fundamental Parameters and Evidence for BinarityMar 20 2002We present the results of recent multicolor photometric and high-resolution spectroscopic observations of the bright Be star Pi Aquarii. Observational data collected from the literature were used to study the star's variations over the last four decades. ... More
The minimum rank of universal adjacency matricesDec 07 2011In this paper we introduce a new parameter for a graph called the {\it minimum universal rank}. This parameter is similar to the minimum rank of a graph. For a graph $G$ the minimum universal rank of $G$ is the minimum rank over all matrices of the form ... More
Stationary distributions of continuous-time Markov chains: a review of theory and truncation-based approximationsSep 12 2019Computing the stationary distributions of a continuous-time Markov chain involves solving a set of linear equations. In most cases of interest, the number of equations is infinite or too large, and cannot be solved analytically or numerically. Several ... More
Cosmic Ray Spectrum and Composition from PeV to EeV from the IceCube Neutrino ObservatoryAug 21 2019The IceCube Neutrino Observatory at the South Pole is a multi-component detector capable of measuring the cosmic ray energy spectrum and composition from PeV to EeV, the energy region typically thought to cover the transition from galactic to extragalactic ... More
Co-spatial Long-slit UV/Optical Spectra of Ten Galactic Planetary Nebulae with HST/STIS I. Description of the Observations, Global Emission-line Measurements, and CNO AbundancesFeb 12 2015We present observations and initial analysis from an HST/STIS program to obtain the first co-spatial, UV-optical spectra of ten Galactic planetary nebulae (PNe). Our primary objective was to measure the critical emission lines of carbon and nitrogen with ... More
The origin of the 'local' 1/4 keV X-ray flux in both charge exchange and a hot bubbleJul 28 2014The Solar neighborhood is the closest and most easily studied sample of the Galactic interstellar medium, an understanding of which is essential for models of star formation and galaxy evolution. Observations of an unexpectedly intense diffuse flux of ... More
Global solutions for semilinear Klein-Gordon equations in FLRW spacetimesJan 16 2014Jul 08 2014We consider waves, which obey the semilinear Klein-Gordon equation, propagating in the Friedmann-Lemaitre-Robertson-Walker spacetimes. The equations in the de Sitter and Einstein-de Sitter spacetimes are the important particular cases. We show the global ... More
Diffusion Limit For The Random Walk Metropolis Algorithm Out Of stationarityMay 19 2014Aug 30 2016The Random Walk Metropolis (RWM) algorithm is a Metropolis- Hastings MCMC algorithm designed to sample from a given target distribution \pi with Lebesgue density on R^N. RWM constructs a Markov chain by randomly proposing a new position (the "proposal ... More
Patterned Probes for High Precision 4D-STEM Bragg MeasurementsJul 11 2019Nanoscale strain mapping by four-dimensional scanning transmission electron microscopy (4D-STEM) relies on determining the precise locations of Bragg-scattered electrons in a sequence of diffraction patterns, a task which is complicated by dynamical scattering, ... More
Graph Minors and the Linear Reducibility of Feynman DiagramsAug 05 2017Aug 27 2017We look at a graph property called reducibility which is closely related to a condition developed by Brown to evaluate Feynman integrals. We show for graphs with a fixed number of external momenta, that reducibility with respect to both Symanzik polynomials ... More
Multitask training with unlabeled data for end-to-end sign language fingerspelling recognitionOct 09 2017Feb 17 2019We address the problem of automatic American Sign Language fingerspelling recognition from video. Prior work has largely relied on frame-level labels, hand-crafted features, or other constraints, and has been hampered by the scarcity of data for this ... More
The Euler characteristic of $\operatorname{Out}(F_n)$Jul 08 2019We prove that the rational Euler characteristic of $\operatorname{Out}(F_n)$ is always negative and its asymptotic growth rate is $\Gamma(n- \frac32)/\sqrt{2\pi} \log^2 n$. This settles a 1987 conjecture of J. Smillie and the second author. We establish ... More
Non-stationary phase of the MALA algorithmAug 30 2016The Metropolis-Adjusted Langevin Algorithm (MALA) is a Markov Chain Monte Carlo method which creates a Markov chain reversible with respect to a given target distribution, ?N, with Lebesgue density on R^N; it can hence be used to approximately sample ... More
The return of the merging galaxy subclusters of El Gordo?Dec 04 2014Jul 28 2015Merging galaxy clusters with radio relics provide rare insights to the merger dynamics as the relics are created by the violent merger process. We demonstrate one of the first uses of the properties of the radio relic to reduce the uncertainties of the ... More
c_2 Invariants of Recursive Families of GraphsJan 05 2017May 22 2017The c_2 invariant, defined by Schnetz in 2011, is an arithmetic graph invariant created towards a better understanding of Feynman integrals. This paper looks at some graph families of interest, with a focus on decompleted toroidal grids. Specifically, ... More
Absorption-Line Systems and Galaxies in Front of the Second Brightest Quasar, PHL 1811Mar 17 2003The extraordinarily bright quasar PHL 1811 at a redshift z = 0.192 provides an attractive opportunity to use ultraviolet absorption-line spectroscopy to study the properties of gas systems in the local universe. An R = 20,000 far-UV spectrum recorded ... More
Safety Analysis for Vehicle Guidance Systems with Dynamic Fault TreesMar 13 2019This paper considers the design-phase safety analysis of vehicle guidance systems. The proposed approach constructs dynamic fault trees (DFTs) to model a variety of safety concepts and E/E architectures for drive automation. The fault trees can be used ... More
The z=0.54 LoBAL Quasar SDSS J085053.12+445122.5: II. The Nature of Partial Covering in the Broad-Absorption-Line OutflowNov 10 2018Apr 30 2019It has been known for 20 years that the absorbing gas in broad absorption line quasars does not completely cover the continuum emission region, and that partial covering must be accounted for to accurately measure the column density of the outflowing ... More
Nonlinear Stabilization via Control Contraction Metrics: a Pseudospectral Approach for Computing GeodesicsJul 14 2016Nov 04 2017Real-time nonlinear stabilization techniques are often limited by inefficient or intractable online and/or offline computations, or a lack guarantee for global stability. In this paper, we explore the use of Control Contraction Metrics (CCM) for nonlinear ... More
Equipartition of rotational and translational energy in a dense granular gasNov 11 2011Experiments quantifying the rotational and translational motion of particles in a dense, driven, 2D granular gas floating on an air table reveal that kinetic energy is divided equally between the two translational and one rotational degrees of freedom. ... More
An experimental test of volume-equilibration between granular systemsMay 12 2009Understanding granular and other athermal systems requires the identification of state variables which consistently predict their bulk properties. A promising approach has been to draw on the techniques of equilibrium statistical mechanics, but to consider ... More
Model distinguishability and inference robustness in mechanisms of cholera transmission and loss of immunityMay 22 2016Mathematical models of cholera and waterborne disease vary widely in their structures, in terms of transmission pathways, loss of immunity, and other features. These differences may yield different predictions and parameter estimates from the same data. ... More
Physical Removal of Metallic Carbon Nanotubes from Nanotube Network Devices Using a Thermal and Fluidic ProcessFeb 01 2013Electronic and optoelectronic devices based on thin films of carbon nanotubes are currently limited by the presence of metallic nanotubes. Here we present a novel approach based on nanotube alkyl functionalization to physically remove the metallic nanotubes ... More
Population Based Training of Neural NetworksNov 27 2017Nov 28 2017Neural networks dominate the modern machine learning landscape, but their training and success still suffer from sensitivity to empirical choices of hyperparameters such as model architecture, loss function, and optimisation algorithm. In this work we ... More
Effect of Geometry on Sensitivity and Offset of AlGaN/GaN and InAlN/GaN Hall-effect SensorsDec 03 2018The current- and voltage-scaled sensitivities and signal-to-noise ratios (SNR) (with respect to thermal noise) of various octagonal AlGaN/GaN and InAlN/GaN Hall-effect sensors were examined in this work. The effect of metal contact lengths on sensitivity ... More
The SDSS-IV in 2014: A Demographic SnapshotMay 22 2015Many astronomers now participate in large international collaborations, and it is important to examine whether these structures foster a scientific climate that is inclusive and diverse. The Committee on the Participation of Women in the Sloan Digital ... More
XMM-Newton Observation of Solar Wind Charge Exchange EmissionApr 19 2004We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by probable C VI lines at 0.37 keV and 0.46 keV, an O VII line at 0.56 keV, O VIII lines at 0.65 keV and ~0.8 keV, Ne IX lines at ~0.92 ... More
Momentum partition between constituents of exotic atoms during laser induced tunneling ionizationMay 18 2015The tunneling ionization of exotic atoms such as muonic hydrogen, muonium and positronium in a strong laser field of circular polarization is investigated taking into account the impact of the motion of the center of mass on the the tunneling ionization ... More
Bias correction in daily maximum and minimum temperature measurements through Gaussian process modelingMay 25 2018May 29 2018The Global Historical Climatology Network-Daily database contains, among other variables, daily maximum and minimum temperatures from weather stations around the globe. It is long known that climatological summary statistics based on daily temperature ... More
A Comprehensive Spectral and Variability Study of Narrow-Line Seyfert 1 Galaxies Observed by ASCA: I. Observations and Time Series AnalysisJul 21 1999(Abridged) I present a comprehensive and uniform analysis of 25 {\it ASCA} observations from 23 Narrow-line Seyfert 1 galaxies. The time series analysis is presented in this paper, Part 1, and the spectral analysis and correlations are presented in the ... More
X-ray Periodicity in AGNDec 27 2004Significant (marginal) detections of periodic signals have been recently reported in 3 (4) Active Galactic Nuclei. Three of the detections were obtained from long EUVE light curves of moderate-luminosity Seyfert galaxies; the fourth was discovered in ... More
ASCA Observations of NLS1sMay 08 2000The study of NLS1s using ASCA has many advantages. A representative sample can be studied; to date, observations of more than 30 NLS1s have been made. ASCA observations are conducted contiguously, so their X-ray variability properties can be studied systematically. ... More
HST STIS Ultraviolet Spectral Evidence of Outflow in Extreme Narrow-line Seyfert 1 Galaxies: II. Modeling and InterpretationFeb 19 2004Apr 11 2004We present modeling to explore the conditions of the broad-line emitting gas in two extreme Narrow-line Seyfert 1 galaxies, using the observational results described in the first paper of this series. Photoionization modeling using Cloudy was conducted ... More
A Comprehensive Spectral and Variability Study of Narrow-Line Seyfert 1 Galaxies Observed by ASCA: II. Spectral Analysis and CorrelationsJul 21 1999(Abridged) I present a comprehensive and uniform analysis of 25 {\it ASCA} observations from 23 Narrow-line Seyfert 1 galaxies. The spectral analysis and correlations are presented in this paper, Part 2; the reduction and time series analysis is presented ... More
Estimate of a Trigonometrical Sum Involving Naturals with Binary Decompositions of a Special KindMay 26 2008Let $\mathbb{N}_0$ be a class of natural numbers whose binary decompositions has even number of 1. We estimate of the sum $\sum\limits_{n\in \mathbf{N}_0,n\le X}\exp(2\pi i \alpha n^2)$.
The Spectral Energy Distributions of Narrow-line Seyfert 1 GalaxiesFeb 27 2004Narrow-line Seyfert 1 galaxies are identified by their uniform optical spectral properties. Studies of samples of NLS1s reveal, however, a range of X-ray spectral and variability behavior, and UV spectral behavior. We describe the range of behavior observed, ... More
STIS Ultraviolet Spectral Evidence for Outflows in Extreme Narrow-Line Seyfert 1 GalaxiesDec 08 2000(abridged) I present and discuss the results of HST STIS observations of IRAS 13224-3809 and 1H 0707-495, two narrow-line Seyfert 1 (NLS1) galaxies. We discovered that high-ionization UV emission lines are much broader and strongly blueshifted compared ... More
Interaction-induced crossover versus finite-size condensation in a weakly interacting trapped one-dimensional Bose gasNov 24 2006Apr 25 2007We discuss the transition from a fully decoherent to a (quasi-)condensate regime in a harmonically trapped weakly interacting 1D Bose gas. By using analytic approaches and verifying them against exact numerical solutions, we find a characteristic crossover ... More
Viewing Earth's surface as a soft matter landscapeMar 11 2019The Earth's surface is composed of a staggering diversity of particulate-fluid mixtures: dry to wet, dilute to dense, colloidal to granular, and attractive to repulsive particles. This material variety is matched by the range of relevant stresses and ... More
Deformation of an Elastic Substrate Due to a Resting Sessile DropletJul 05 2016On a sufficiently-soft substrate, a resting fluid droplet will cause significant deformation of the substrate. This deformation is driven by a combination of capillary forces at the contact line and the fluid pressure at the solid surface. These forces ... More
Correlations between electrical and mechanical signals during granular stick-slip eventsJul 09 2013Powders and grains exhibit unpredictable jamming-to-flow transitions that manifest themselves on geophysical scales in catastrophic slip events such as landslides and earthquakes, and on laboratory/industrial scales in profound processing difficulties. ... More
Characterization of a Freezing/Melting Transition in a Vibrated and Sheared Granular MediumDec 21 2005We describe experiments on monodisperse spherical particles in an annular cell geometry, vibrated from below and sheared from above. This system shows a freezing/melting transition such that under sufficient vibration a crystallized state is observed, ... More
Simulating Surfactant Spreading: Impact of a Physically Motivated Equation of StateFeb 17 2016For more than two decades, a single model for the spreading of a surfactant-driven thin liquid film has dominated the applied mathematics literature on the subject. Recently, through the use of fluorescently-tagged lipids, it has become possible to make ... More
Treewidth Bounds for Planar Graphs Using Three-Sided BramblesJun 26 2017Square grids play a pivotal role in Robertson and Seymour's work on graph minors as planar obstructions to small treewidth. We introduce a three-sided bramble in a plane graph called a net, which generalizes the standard bramble of crosses in a square ... More
The Birth of an Ultra-Luminous X-ray Source in M83Mar 11 2012A previously undetected X-ray source (L_X<10**36 erg/s) in the strongly star-forming galaxy M83 entered an ultraluminous state between August 2009 and December 2010. It was first seen with Chandra on 23 December 2010 at L_X ~ 4 10**39 ergs/s, and has ... More
Some results on an algebro-geometric condition on graphsFeb 01 2016Jan 10 2017Paolo Aluffi, inspired by an algebro-geometric problem, asked when the Kirchhoff polynomial of a graph is in the Jacobian ideal of the Kirchhoff polynomial of the same graph with one edge deleted. We give some results on which graph-edge pairs have this ... More
Cross-correlation of CFHTLenS galaxy catalogue and Planck CMB lensing using the halo model prescriptionOct 01 2015Nov 19 2015I cross-correlate the galaxy counts from the Canada-France Hawaii Telescope Lensing Survey (CFHTLenS) galaxy catalogue and Cosmic Microwave Background (CMB) convergence from the Planck data release 1 (2013) and 2 (2015), following the work of Omori & ... More
IceAct, small Imaging Air Cherenkov Telescopes for IceCubeAug 29 2019IceAct is a proposed surface array of cost effective and compact Silicon Photomultipliers (SiPM) based small-size (50 cm) Imaging Air Cherenkov Telescopes above the IceCube in-ice detector. In coincidence with the in-ice and surface components of IceCube ... More
Visualizing Movement Control Optimization LandscapesSep 17 2019Sep 18 2019A large body of animation research focuses on optimization of movement control, either as action sequences or policy parameters. However, as closed-form expressions of the objective functions are often not available, our understanding of the optimization ... More
Cut vertices in commutative graphsJul 28 2003Dec 01 2004The homology of Kontsevich's commutative graph complex parameterizes finite type invariants of odd dimensional manifolds. This {\it graph homology} is also the twisted homology of Outer Space modulo its boundary, so gives a nice point of contact between ... More
Binary Additive Problems Involving Naturals with Binary Decompositions of a Special KindMay 26 2008Let $h$ and $l$ be integers such that $0\le h\le 2$, $0\le l\le 4$. We obtain asymptotic formulas for the numbers of solutions of the equations $n-3m=h$, $n-5m=l$ in positive integers $m$ and $n$ of a special kind, $m\le X$.
The Detectability of Moons of Extra-Solar PlanetsSep 25 2011The detectability of moons of extra-solar planets is investigated, focussing on the time-of-arrival perturbation technique, a method for detecting moons of pulsar planets, and the photometric transit timing technique, a method for detecting moons of transiting ... More
Spitzer mapping of molecular hydrogen pure rotational lines in NGC 1333: A detailed study of feedback in star formationApr 03 2009We present mid-infrared spectral maps of the NGC 1333 star forming region, obtained with the the Infrared Spectrometer on board the Spitzer Space Telescope. Eight pure H2 rotational lines, from S (0) to S (7), are detected and mapped. The H2 emission ... More
Quantum Corrections to the Gravitational BackreactionDec 18 2017Effective Field Theory techniques are used to study the leading order quantum corrections to the gravitational wave backreaction. The effective stress-energy tensor is calculated and it is shown that it has a non-vanishing trace that contributes to the ... More
Selection and Coalescence in a Finite State ModelJan 04 2017To introduce selection into a model of coalescence, I explore the use of modified integer partitions that allow the identification of a preferred lineage. I show that a partition-partition transition matrix, along with Monte Carlo discrete time kinetics, ... More
Superconducting monolayer deposited on substrate: effects of the spin-orbit coupling induced by proximity effectsJan 24 2018The spin-orbit coupling can lead to exotic states of matter and unexpected behavior of the system properties. In this paper, we investigate the influence of spin-orbit coupling induced by proximity effects on a monolayer of superconductor (with s-wave ... More
Semantic query-by-example speech search using visual groundingApr 15 2019A number of recent studies have started to investigate how speech systems can be trained on untranscribed speech by leveraging accompanying images at training time. Examples of tasks include keyword prediction and within- and across-mode retrieval. Here ... More
Visualizing Movement Control Optimization LandscapesSep 17 2019A large body of animation research focuses on optimization of movement control, either as action sequences or policy parameters. However, as closed-form expressions of the objective functions are often not available, our understanding of the optimization ... More
Globally $F$-regular and log Fano varietiesMay 04 2009Dec 23 2009We prove that every globally $F$-regular variety is log Fano. In other words, if a prime characteristic variety $X$ is globally $F$-regular, then it admits an effective $\bQ$-divisor $\Delta$ such that $-K_X - \Delta$ is ample and $(X, \Delta)$ has controlled ... More
Lattice analogues of W-algebras and Classical Integrable EquationsMar 30 1993We propose a regular way to construct lattice versions of $W$-algebras, both for quantum and classical cases. In the classical case we write the algebra explicitly and derive the lattice analogue of Boussinesq equation from the Hamiltonian equations of ... More
A valuation theoretic characterization of recursively saturated real closed fieldsDec 31 2012We give a valuation theoretic characterization for a real closed field to be recursively saturated. Our result extends the characterization of Harnik and Ressayre \cite{hr} for a divisible ordered abelian group to be recursively saturated.
Random-step Markov processesOct 06 2014We explore two notions of stationary processes. The first is called a random-step Markov process in which the stationary process of states, $(X_i)_{i \in \mathbb{Z}}$ has a stationary coupling with an independent process on the positive integers, $(L_i)_{i ... More
Non-smooth gravity and parity violationFeb 07 2019A conservative extension of general relativity is proposed by alleviating the differentiability of the metric and allowing for non-smooth solutions. We show that these metrics break some symmetries of the Riemann tensor, yielding a new scalar curvature ... More
The two-body potential of Vainshtein screened theoriesMay 17 2019Adding a light scalar degree of freedom to General Relativity often induces a fifth force whose magnitude is strongly constrained by laboratory experiments and solar system tests. The Vainshtein screening mechanism ensures that the effects of this supplementary ... More
Next Generation of Telescopes or Dynamics Required to Determine if Exo-Moons have Prograde or Retrograde OrbitsJul 16 2014We survey the methods proposed in the literature for detecting moons of extrasolar planets in terms of their ability to distinguish between prograde and retrograde moon orbits, an important tracer of moon formation channel. We find that most moon detection ... More
Carbon isotope fractionation in protoplanetary disksDec 01 2008We investigate the gas-phase and grain-surface chemistry in the inner 30 AU of a typical protoplanetary disk using a new model which calculates the gas temperature by solving the gas heating and cooling balance and which has an improved treatment of the ... More
Simulation of the Elastic Properties of Reinforced Kevlar-Graphene CompositesAug 01 2012The compressive strength of unidirectional fiber composites in the form of Kevlar yarn with a thin outer layer of graphene was investigated and modeled. Such fiber structure may be fabricated by using a strong chemical bond between Kevlar yarn and graphene ... More
One-Up On L1: Can X-rays Provide Longer Advanced Warning of Solar Wind Flux Enhancements Than Upstream Monitors?Feb 17 2005Observations of strong solar wind proton flux correlations with ROSAT X-ray rates along with high spectral resolution Chandra observations of X-rays from the dark Moon show that soft X-ray emission mirrors the behavior of the solar wind. In this paper, ... More
Measurement of superluminal phase and group velocities of Bessel beams in free spaceNov 27 2008We report on an interferometry-based measurement of the phase and group velocities of optical Bessel beams, providing confirmation of their superluminal character in the non-diffractive region. The measurements were performed in free space with a continuous ... More
Benzene formation in the inner regions of protostellar disksDec 08 2006Benzene (c-C6H6) formation in the inner 3 AU of a protostellar disk can be efficient, resulting in high abundances of benzene in the midplane region. The formation mechanism is different to that found in interstellar clouds and in protoplanetary nebulae, ... More
Photoionization Models of the Broad-line RegionJan 15 2007The strong broad emission lines in the optical and UV spectra of Active Galactic Nuclei (AGN) are important for several reasons. Not only do they give us information about the structure of the AGN, their properties are now used to estimate black hole ... More
Polymer adhesion: first-principles calculations of the adsorption of organic molecules onto Si surfacesApr 16 2007The structures and energetics of organic molecules adsorbed onto clean and H-passivated Si(001)-(2$\times$1) surfaces have been calculated using density functional theory. For benzene adsorbed on the clean Si surface the tight-bridge structure was found ... More
Evolution of cooperation on an epitheliumDec 06 2018Cooperation is prevalent in nature, not only in the context of social interactions within the animal kingdom, but also on the cellular level. In cancer for example, tumour cells can cooperate by producing growth factors. The evolution of cooperation has ... More
Flow-Driven Formation of Solid-like Microsphere HeapsJul 31 2012We observe the formation of heaps of repulsive microspheres, created by flowing a colloidal microsphere suspension towards a flat-topped ridge placed within a quasi two-dimensional microfluidic channel. This configuration allows for both shear and normal ... More
Nonaffine deformation under compression and decompression of a flow-stabilized solidMar 30 2016Understanding the particle-scale transition from elastic deformation to plastic flow is central to making predictions about the bulk material properties and response of disordered materials. To address this issue, we perform experiments on flow-stabilized ... More
Clique immersion in graph productsAug 27 2019Let $G,H$ be graphs and $G*H$ represent a particular graph product of $G$ and $H$. We define $im(G)$ to be the largest $t$ such that $G$ has a $K_t$-immersion and ask: given $im(G)=t$ and $im(H)=r$, how large is $im(G*H)$? Best possible lower bounds are ... More
A Deep Chandra ACIS Survey of M83Apr 11 2014We have obtained a series of deep X-ray images of the nearby galaxy M83 using Chandra, with a total exposure of 729 ks. Combining the new data with earlier archival observations totaling 61 ks, we find 378 point sources within the D25 contour of the galaxy. ... More
A Newly Recognized Very Young Supernova Remnant in M83Dec 30 2014As part of a spectroscopic survey of supernova remnant candidates in M83 using the Gemini-South telescope and GMOS, we have discovered one object whose spectrum shows very broad lines at H$\alpha$, [O~I] 6300,6363, and [O~III] 4959,5007, similar to those ... More