Results for "David L. Ndzi"

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Multi-View Region Adaptive Multi-temporal DMM and RGB Action RecognitionApr 12 2019Human action recognition remains an important yet challenging task. This work proposes a novel action recognition system. It uses a novel Multiple View Region Adaptive Multi-resolution in time Depth Motion Map (MV-RAMDMM) formulation combined with appearance ... More
Improving AODV Performance using Dynamic Density Driven Route Request ForwardingJul 19 2011Ad-hoc routing protocols use a number of algorithms for route discovery. Some use flooding in which a route request packet (RREQ) is broadcasted from a source node to other nodes in the network. This often leads to unnecessary retransmissions, causing ... More
Finding cool subdwarfs using a V-J reduced proper-motion diagram: Stellar parameters for 91 candidatesJun 03 2003We present the results of a search for cool subdwarfs for which our candidates were drawn from a V-J reduced proper-motion diagram constructed by Salim & Gould (2002). Kinematic (U, V, and W) and self-consistent stellar parameters (Teff, log g, [Fe/H], ... More
A search for cool subdwarfs: Stellar parameters for 134 candidatesSep 17 2002The results of a search for cool subdwarfs are presented. Kinematic (U, V, and W) and stellar parameters (Teff, log g, [Fe/H], and V_t) are derived for 134 candidate subdwarfs based on high resolution spectra. The observed stars span 4200K < Teff < 6400K ... More
Misconceptions About General Relativity in Theoretical Black Hole AstrophysicsApr 09 2010The fundamental role played by black holes in our study of microquasars, gamma ray bursts, and the outflows from active galactic nuclei requires an appreciation for, and at times some in-depth analysis of, curved spacetime. We highlight misconceptions ... More
Theory of liquid crystal anchoring at a porous surfaceApr 05 2006Using classical density functional theory (DFT) the effect of bringing a liquid crystal (LC) into contact with a porous substrate or matrix is investigated. The DFT used is a combination of the Onsager approximation to evaluate the excess free energy ... More
The Association of Jet Production with Geometrically Thick Accretion Flows and Black Hole RotationOct 12 2000A model is presented in which the strongest radio-emitting jet outflows are produced in black hole systems when the accretion is a geometrically thick ($H/R \sim 1$) inflow ({\it e.g.}, ADAF, CDAF) {\em and} if the black hole is rotating. For galactic ... More
Grand Unification of AGN and the Accretion and Spin ParadigmsAug 26 1999While attempts to unify certain classes of AGN using orientation and environmental effects have been successful, it is widely recognized that intrinsic properties of the accreting black hole system also must play a role in determining the appearance of ... More
Vortex arrays in a rotating superfluid Fermi gasOct 05 2004The behavior of a dilute two-component superfluid Fermi gas subjected to rotation is investigated within the context of a weak-coupling BCS theory. The microscopic properties at finite temperature are obtained by iterating the Bogoliubov-de Gennes equations ... More
Spin-0 to Spin-1/2 Deterministic Dynamics: From Relativistic Quantum Potential to Quantum Stress TensorSep 11 2016Oct 10 2016The Bohm/de Broglie theory of deterministic non-relativistic quantum mechanics is broadened to accommodate the free-particle Dirac equation. As with the spin-0 theory, an effective particle rest-mass scalar field in the presence of the spin-1/2 pilot ... More
Electrostatic model of atomic ordering in complex perovskite alloysJun 23 1998We present a simple ionic model which successfully reproduces the various types of compositional long-range order observed in a large class of complex insulating perovskite alloys. The model assumes that the driving mechanism responsible for the ordering ... More
Advanced Optimal Control Methods for Spin SystemsMar 28 2018Apr 26 2018Work within this thesis advances optimal control algorithms for application to magnetic resonance systems. Specifically, presenting a quadratically convergent version of the gradient ascent pulse engineering method. The work is formulated in a superoperator ... More
On the Negative Case of the Singular Yamabe ProblemJan 16 1996The negative case of the Singular Yamabe Problem concerns the existence and behavior of complete metrics with constant negative scalar curvature on the complement of a closed set in a compact Riemannian manifold which are conformally equivalent to a smooth ... More
The Limiting Distribution of the Number of Block Pairs in Type B Set PartitionsAug 05 2011It is a classical result of Harper that the limiting distribution of the number of blocks in partitions of the set $\{1, 2,..., n\}$ is normal. In this paper, using the saddle point method we prove the normality of the limiting distribution of the number ... More
Implicit Ligand Theory: Rigorous Binding Free Energies and Thermodynamic Expectations from Molecular DockingAug 24 2012A rigorous formalism for estimating noncovalent binding free energies and thermodynamic expectations from calculations in which receptor configurations are sampled independently from the ligand is derived. Due to this separation, receptor configurations ... More
Multiple Potentials of Mean Force from Biased Experiments Along a Single CoordinateJan 05 2007Mar 20 2007External biasing forces are often applied to enhance sampling in regions of phase space which would otherwise be rarely observed. While the typical goal of these experiments is to calculate the potential of mean force (PMF) along the biasing coordinate, ... More
Protein-Ligand Binding Potential of Mean Force Calculations with Hamiltonian Replica Exchange on Alchemical Interaction GridsJul 14 2015A binding potential of mean force (BPMF) is a free energy of noncovalent association in which one binding partner is flexible and the other is rigid. I have developed a method to calculate BPMFs for protein-ligand systems. The method is based on replica ... More
Disk Destruction and (Re)-Creation in the Magellanic CloudsOct 24 2013Unlike most satellite galaxies in the Local Group that have long lost their gaseous disks, the Magellanic Clouds are gas-rich dwarf galaxies most-likely on their first pericentric passage allowing us to study disk evolution on the smallest scales. The ... More
Multi-Dimensional Astrophysical Structural and Dynamical Analysis I. Development of a Nonlinear Finite Element ApproachJun 19 1998Nov 10 1998A new field of numerical astrophysics is introduced which addresses the solution of large, multidimensional structural or slowly-evolving problems (rotating stars, interacting binaries, thick advective accretion disks, four dimensional spacetimes, etc.). ... More
Cooling ultracold bosons in optical lattices by spectral transformOct 24 2008It is shown theoretically how to directly obtain the energy distribution of a weakly interacting gas of bosons confined in an optical lattice in the tight-binding limit. This is accomplished by adding a linear potential to a suitably prepared lattice, ... More
The use of conflicts in searching Bayesian networksMar 06 2013This paper discusses how conflicts (as used by the consistency-based diagnosis community) can be adapted to be used in a search-based algorithm for computing prior and posterior probabilities in discrete Bayesian Networks. This is an "anytime" algorithm, ... More
A Gamma-Ray Burst Trigger ToolkitMay 31 2002Jul 08 2002(Abbreviated) The detection rate of a GRB detector can be increased by using a count rate trigger with many accumulation times Dt and energy bands DE, but the nominal sensitivity is less important than how much fainter a burst could be at the detection ... More
Sky Coverage and Burst RepetitionJan 09 1996To investigate the repeater content of gamma ray burst samples I develop two models where sources burst at a constant average rate. I find that the sky coverage affects the number of repeaters in a sample predominantly through the detector livetime, and ... More
Gamma-Ray Burst Spectral Evolution Through Crosscorrelations of Discriminator Light CurvesApr 21 1997Gamma-ray burst spectra usually show hard-to-soft evolution within intensity spikes and from spike to spike. The techniques used to study spectral evolution often lack sufficient temporal resolution to determine the nature of this evolution. By comparing ... More
On the components of the gauge group for PU(r)-bundlesNov 21 2013We discuss a general procedure for using characteristic classes to study the components of the gauge group for a principal G-bundle. To illustrate this, we work out the case where G is the projective unitary group.
Mass Constraints from Eclipse Timing in Double White Dwarf BinariesJun 18 2010I demonstrate that an effect similar to the Roemer delay, familiar from timing radio pulsars, should be detectable in the first eclipsing double white dwarf (WD) binary, NLTT 11748. By measuring the difference of the time between the secondary and primary ... More
Determining All Universal TilersOct 08 2011A universal tiler is a convex polyhedron whose every cross-section tiles the plane. In this paper, we introduce a certain slight-rotating operation for cross-sections of pentahedra. Based on a selected initial cross-section and by applying the slight-rotating ... More
On Universal TilersSep 05 2011A famous problem in discrete geometry is to find all monohedral plane tilers, which is still open to the best of our knowledge. This paper concerns with one of its variants that to determine all convex polyhedra whose every cross-section tiles the plane. ... More
Exploiting the Rule Structure for Decision Making within the Independent Choice LogicFeb 20 2013This paper introduces the independent choice logic, and in particular the "single agent with nature" instance of the independent choice logic, namely ICLdt. This is a logical framework for decision making uncertainty that extends both logic programming ... More
Context-Specific Approximation in Probabilistic InferenceJan 30 2013There is evidence that the numbers in probabilistic inference don't really matter. This paper considers the idea that we can make a probabilistic model simpler by making fewer distinctions. Unfortunately, the level of a Bayesian network seems too coarse; ... More
Comparison of the Gamma-Ray Burst Sensitivity of Different DetectorsDec 19 2002Jan 24 2003Gamma-ray burst detectors are sensitive at different energies, complicating the comparison of the burst populations that they detect. The instrument teams often report their detector sensitivities in their instruments' energy band. I propose that sensitivities ... More
Georges Lemaitre and Stiglers Law of EponymyJun 20 2011Nov 09 2012One of the greatest discoveries of modern times is that of the expanding Universe, almost invariably attributed to Hubble (1929). What is not widely known is that the original treatise by Lemaitre (1927) contained a rich fusion of both theory and of observation. ... More
Ohm's Law in the Fast Lane: General Relativistic Charge DynamicsDec 02 2003Fully relativistic and causal equations for the flow of charge in curved spacetime are derived. It is believed that this is the first set of equations to be published that correctly describes the flow of charge, and evolution of the electromagnetic field, ... More
Constrained Transport Algorithms for Numerical Relativity. I. Development of a Finite Difference SchemeDec 02 2003A scheme is presented for accurately propagating the gravitational field constraints in finite difference implementations of numerical relativity. The method is based on similar techniques used in astrophysical magnetohydrodynamics and engineering electromagnetics, ... More
The AKARI Deep Field South: Pushing to High RedshiftJan 06 2016The AKARI Deep Field South (ADF-S) is a large extragalactic survey field that is covered by multiple instruments, from optical to far-IR and radio. I summarise recent results in this and related fields prompted by the release of the Herschel far-IR/submm ... More
Perfect quantum state transfer with spinor bosons on weighted graphsJun 08 2006A duality between the properties of many spinor bosons on a regular lattice and those of a single particle on a weighted graph reveals that a quantum particle can traverse an infinite hierarchy of networks with perfect probability in polynomial time, ... More
The Chern-Simons invariants for the double of a compression bodyOct 22 2016Given a 3-manifold that can be written as the double of a compression body, we compute the Chern-Simons critical values for arbitrary compact connected structure groups. We also show that the moduli space of flat connections is connected when there are ... More
An index relation for the quilted Atiyah-Floer conjectureNov 16 2013May 07 2015Given a closed, connected, oriented 3-manifold with positive first Betti number, one can define an instanton Floer group as well as a quilted Lagrangian Floer group. Each of these is equipped with a chain level grading. We show that the gradings agree. ... More
Synopsis of DualityAug 07 2018Properties and examples of the dual transformation between two planes, which is such that the coordinates of a point in the original plane give the coefficients of a line in the dual plane and the coefficients of a line in the original plane give the ... More
Higher-rank instanton cohomology and the quilted Atiyah-Floer conjectureNov 21 2013May 07 2015Given a closed, connected, oriented 3-manifold with positive first Betti number, one can define an instanton Floer group as well as a quilted Lagrangian Floer group. The quilted Atiyah-Floer conjecture states that these cohomology groups are isomorphic. ... More
Invariants for the Modular Cyclic Group of Prime Order via Classical Invariant TheoryDec 06 2009Oct 14 2011Let $F$ be any field of characteristic $p$. It is well-known that there are exactly $p$ inequivalent indecomposable representations $V_1,V_2,...,V_p$ of $C_p$ defined over $F$. Thus if $V$ is any finite dimensional $C_p$-representation there are non-negative ... More
Weitzenböck derivations of nilpotency 3Nov 01 2010Mar 14 2012We consider a Weitzenb\"ock derivation $\Delta$ acting on a polynomial ring $R=K[\xi_1,\xi_2,...,\xi_m]$ over a field $K$ of characteristic 0. The $K$-algebra $R^\Delta = \{h \in R \mid \Delta(h) = 0\}$ is called the algebra of constants. Nowicki considered ... More
Chern-simons forms on associated bundles, and boundary termsJan 09 2006Let $E$ be a principle bundle over a compact manifold $M$ with compact structural group $G$. For any $G$-invariant polynomial $P$, The transgressive forms $TP(\omega)$ defined by Chern and Simons are shown to extend to forms $\Phi P(\omega)$ on associated ... More
Compactness results for neck-stretching limits of instantonsDec 07 2012May 07 2015We prove that, under a suitable degeneration of the metric, instantons converge to holomorphic quilts. To prove the main results, we develop estimates for the Yang-Mills heat flow on surfaces and cobordisms.
Emerging applications of geometric multiscale analysisDec 01 2002Classical multiscale analysis based on wavelets has a number of successful applications, e.g. in data compression, fast algorithms, and noise removal. Wavelets, however, are adapted to point singularities, and many phenomena in several variables exhibit ... More
A Framework for Decision-Theoretic Planning I: Combining the Situation Calculus, Conditional Plans, Probability and UtilityFeb 13 2013This paper shows how we can combine logical representations of actions and decision theory in such a manner that seems natural for both. In particular we assume an axiomatization of the domain in terms of situation calculus, using what is essentially ... More
Burst Detector Sensitivity: Past, Present & FutureJan 19 2006I compare the burst detection sensitivity of CGRO's BATSE, Swift's BAT, the GLAST Burst Monitor (GBM) and EXIST as a function of a burst's spectrum and duration. A detector's overall burst sensitivity depends on its energy sensitivity and set of accumulations ... More
Intensity Distributions of Gamma-Ray BurstsJun 01 2001Observations of individual bursts chosen by the vagaries of telescope availability demonstrated that bursts are not standard candles and that their apparent energy can be as great as 10^54 erg. However, determining the distribution of their apparent energy ... More
The Energy Distribution of Gamma-Ray BurstsMay 15 2001The distribution of the apparent total energy emitted by a gamma-ray burst reflects not only the distribution of the energy actually released by the burst engine, but also the distribution of beaming angles. Using the observed energy fluences, the detection ... More
CESR Test AcceleratorAug 10 2013The Cornell Electron Storage Ring (CESR) was reconfigured in 2008 as a test accelerator to investigate the physics of ultra-low emittance damping rings. During the approximately 40 days/year available for dedicated operation as a test accelerator, specialized ... More
Maximally entangled gapped ground state of lattice fermionsDec 21 2011Entanglement between the constituents of a quantum system is an essential resource in the implementation of many quantum processes and algorithms. Indeed, universal quantum computation is possible by measuring individual qubits comprising highly entangled ... More
The Theory of Relativistic Jet Formation in Galactic Sources: Towards a Unified MOdelDec 02 2003I review recent progress in the theory of relativistic jet production. The presently favored mechanism is an electrodynamic one, in which charged plasma is accelerated by electric fields that are generated by a rotating magnetic field. The most pressing ... More
Comment on "Hubble flow variations as a test for inhomogeneous cosmology"Dec 04 2018Saulder et al [arXiv:1811.11976] have performed a novel observational test of the local expansion of the Universe for the standard cosmology as compared to an alternative model with differential cosmic expansion. Their analysis employs mock galaxy samples ... More
On colored set partitions of type $B_n$Jan 05 2015Generalizing Reiner's notion of set partitions of type $B_n$, we define colored $B_n$-partitions by coloring the elements in and not in the zero-block respectively. Considering the generating function of colored $B_n$-partitions, we get the exact formulas ... More
Representing Bayesian Networks within Probabilistic Horn AbductionMar 20 2013This paper presents a simple framework for Horn clause abduction, with probabilities associated with hypotheses. It is shown how this representation can represent any probabilistic knowledge representable in a Bayesian belief network. The main contributions ... More
Post-Launch Analysis of Swift's Gamma-Ray Burst Detection SensitivityFeb 12 2006The dependence of Swift's detection sensitivity on a burst's temporal and spectral properties shapes the detected burst population. Using simplified models of the detector hardware and the burst trigger system I find that Swift is more sensitive to long, ... More
Burst Populations and Detector SensitivityDec 12 2003The F_T (peak bolometric photon flux) vs. E_p (peak energy) plane is a powerful tool to compare the burst populations detected by different detectors. Detector sensitivity curves in this plane demonstrate which burst populations the detectors will detect. ... More
The Gamma-Ray Burst MysteryDec 15 1997Gamma-ray bursts are transient events from beyond the solar system. Besides the allure of their mysterious origin, bursts are physically fascinating because they undoubtedly require exotic physics. Optical transients coincident with burst positions show ... More
The virtual crystal approximation revisited: Application to dielectric and piezoelectric properties of perovskitesAug 25 1999We present an approach to the implementation of the virtual crystal approximation (VCA) for the study of properties of solid solutions in the context of density-functional methods. Our approach can easily be applied to any type of pseudopotential, and ... More
Optimized replica gas estimation of absolute integrals and partition functionsFeb 03 2010In contrast with most Monte Carlo integration algorithms, which are used to estimate ratios, the replica gas identities recently introduced by Adib enable the estimation of absolute integrals and partition functions using multiple copies of a system and ... More
Density-Dependent Analysis of Nonequilibrium Paths Improves Free Energy EstimatesJan 21 2009Apr 29 2009When a system is driven out of equilibrium by a time-dependent protocol that modifies the Hamiltonian, it follows a nonequilibrium path. Samples of these paths can be used in nonequilibrium work theorems to estimate equilibrium quantities, such as free ... More
The Theory and Simulation of Relativistic Jet Formation: Towards a Unified Model For Micro- and MacroquasarsDec 02 2003I review recent progress in the theory of relativistic jet production, with special emphasis on unifying black hole sources of stellar and supermassive size. Observations of both classes of objects, as well as theoretical considerations, indicate that ... More
A Magnetically-Switched, Rotating Black Hole Model For the Production of Extragalactic Radio Jets and the Fanaroff and Riley Class DivisionOct 21 1998Jul 30 1999A model is presented in which both Fanaroff and Riley class I and II extragalactic jets are produced by magnetized accretion disk coronae in the ergospheres of rotating black holes. While the jets are produced in the accretion disk itself, the output ... More
Spin-0 to Spin-1/2 Deterministic Dynamics: From Relativistic Quantum Potential to Quantum Stress TensorSep 11 2016Nov 29 2016The Bohm/de Broglie theory of deterministic non-relativistic quantum mechanics is broadened to accommodate the free-particle Dirac equation. As with the spin-0 theory, an effective particle rest-mass scalar field in the presence of the spin-1/2 pilot ... More
The AKARI Deep Field South: A New Home for Multiwavelength Extagalactic AstronomyAug 22 2012The importance of multiwavelength astronomical surveys is discussed in the context of galaxy evolution. The AKARI Deep Field South (ADF-S) is a new, well placed survey field that is already the subject of studies at a wide range of wavelengths. A number ... More
The Yang-Mills flow for cylindrical end 4-manifoldsMar 01 2016We establish various existence and uniqueness results for the Yang-Mills flow on cylindrical end 4-manifolds. We also show long-time existence and infinite-time convergence under certain hypotheses on the underlying data.
Complete caps in projective space which are disjoint from a subspace of codimension twoMar 02 2004Working over the field of order 2 we consider those complete caps (maximal sets of points with no three collinear) which are disjoint from some codimension 2 subspace of projective space. We derive restrictive conditions which such a cap must satisfy ... More
Bayesian views of generalized additive modellingFeb 04 2019Links between frequentist and Bayesian approaches to smoothing were highlighted early on in the smoothing literature, and power much of the machinery that underlies the modern generalized additive modelling framework (implemented in software such as the ... More
Mg isotope ratios in giant stars of the globular clusters M 13 and M 71Oct 19 2005We present Mg isotope ratios in 4 red giants of the globular cluster M 13 and 1 red giant of the globular cluster M 71 based on spectra obtained with HDS on the Subaru Telescope. We confirm earlier results by Shetrone that for M 13, the ratio varies from ... More
A Magnetohydrodynamic Model of the M87 Jet I: Superluminal Knot Ejections from HST-1 as Trails of Quad Relativistic MHD ShocksAug 20 2010This is the first in a series of papers that introduces a new paradigm for understanding the jet in M87: a collimated relativistic flow in which strong magnetic fields play a dominant dynamical role. Here wefocus on the flow downstream of HST-1 - an essentially ... More
Error-correcting one-way quantum computation with global entangling gatesAug 05 2009We present an approach to one-way quantum computation (1WQC) that can compensate for single-qubit errors, by encoding the logical information residing on physical qubits into five-qubit error-correcting code states. A logical two-qubit cluster state that ... More
Edge local complementation for logical cluster statesMay 19 2011A method is presented for the implementation of edge local complementation in graph states, based on the application of two Hadamard operations and a single controlled-phase (CZ) gate. As an application, we demonstrate an efficient scheme to construct ... More
High Resolution Optical Spectroscopy of a Newly Discovered Post-AGB Star with a Surprising Metallicity in the Globular Cluster M79Jun 19 2009Jul 15 2009An abundance analysis based on a high-resolution spectrum is presented for a newly discovered post-AGB star in the globular cluster M79. The surprising result is that the iron abundance of the star is apparently about 0.6 dex less than that of the cluster's ... More
Crowding effects on the mechanical stability and unfolding pathways of UbiquitinNov 05 2008The interior of cells is crowded thus making it important to assess the effects of macromolecules on the folding of proteins. Using the Self-Organized Polymer (SOP) model, which is a coarse-grained representation of polypeptide chains, we probe the mechanical ... More
Carbon and Oxygen abundances across the Hertzsprung gapJul 08 2014We derived atmospheric parameters and spectroscopic abundances for C and O for a large sample of stars located in the Hertzsprung gap in the Hertzsprung-Russell Diagram in order to detect chemical peculiarities and get a comprehensive overview of the ... More
On the Origin of SulfurOct 05 2005We present our work on the halo evolution of sulfur, based on observations of the S I lines around 9220 A for ten stars for which the S abundance was obtained previously from much weaker S I lines at 8694 A. We cannot confirm the rise and the high [S/Fe] ... More
3-3-1 Models with Unique Lepton GenerationsSep 20 2005Nov 08 2005We study previously unconsidered 3-3-1 models which are characterized by each lepton generation having a different representation under the gauge group. Flavor-changing neutral currents in the lepton sector occur in these models. To satisfy constraints ... More
Modular Invariants of a Vector and a Covector: a proof of a conjecture of Bonnafé and KemperNov 11 2015Aug 14 2016Consider a finite dimensional vector space $V$ over a finite field $\mathbb{F}_q$. We give a minimal generating set for the ring of invariants $\mathbb{F}_q[V \oplus V^*]^{\text{GL}(V)}$, and show that this ring is a Gorenstein ring but is not a complete ... More
Ricci flow on three-dimensional, unimodular metric Lie algebrasSep 04 2009We give a global picture of the Ricci flow on the space of three-dimensional, unimodular, nonabelian metric Lie algebras considered up to isometry and scaling. The Ricci flow is viewed as a two-dimensional dynamical system for the evolution of structure ... More
Volume-minimizing foliations on spheresFeb 18 2004The volume of a k-dimensional foliation $\mathcal{F}$ in a Riemannian manifold $M^{n}$ is defined as the mass of image of the Gauss map, which is a map from M to the Grassmann bundle of k-planes in the tangent bundle. Generalizing a construction by Gluck ... More
Magnetic Field-Decay-Induced Electron Captures: a Strong Heat Source in Magnetar CrustsOct 14 2009Dec 03 2009We propose a new heating mechanism in magnetar crusts. Magnetars' crustal magnetic fields are much stronger than their surface fields; therefore, magnetic pressure partially supports the crust against gravity. The crust loses magnetic pressure support ... More
All-optical transistor action by off-resonant activation at laser thresholdOct 06 2009The development of viable all-optical data processing systems has immense importance for both the computing and telecommunication industries, but device realization remains elusive. In this Letter, we propose an innovative mechanism deployed as a basis ... More
The Optimal Hard Threshold for Singular Values is 4/sqrt(3)May 24 2013Jun 04 2014We consider recovery of low-rank matrices from noisy data by hard thresholding of singular values, where singular values below a prescribed threshold $\lambda$ are set to 0. We study the asymptotic MSE in a framework where the matrix size is large compared ... More
A Magnetohydrodynamic Model of The M87 Jet. II. Self-consistent Quad-shock Jet Model for Optical Relativistic Motions and Particle AccelerationMar 14 2014We describe a new paradigm for understanding both relativistic motions and particle acceleration in the M87 jet: a magnetically dominated relativistic flow that naturally produces four relativistic magnetohydrodynamic (MHD) shocks (forward/reverse fast ... More
The outer atmosphere of the M-type supergiant alpha Orionis: KI 7699A emissionMar 13 2002Spatially-resolved high-resolution long-slit spectra of Betelgeuse's circumstellar shell are described for a spectral window centered on the 7699\AA resonance line of neutral potassium. The K I emission from resonance fluorescent scattering of photospheric ... More
A Max-Plus Model of Asynchronous Cellular AutomataFeb 13 2015This paper presents a new framework for asynchrony. This has its origins in our attempts to better harness the internal decision making process of cellular automata (CA). Thus, we show that a max-plus algebraic model of asynchrony arises naturally from ... More
Probabilistic Semantics and DefaultsMar 27 2013There is much interest in providing probabilistic semantics for defaults but most approaches seem to suffer from one of two problems: either they require numbers, a problem defaults were intended to avoid, or they generate peculiar side effects. Rather ... More
Atmospheric composition of weak G band stars: CNO and Li abundancesJan 23 2013We determined the chemical composition of a large sample of weak G band stars -- a rare class of G and K giants of intermediate mass with unusual abundances of C, N, and Li. We have observed 24 weak G band stars with the 2.7 m Harlan J. Smith Telescope ... More
Surfactant and gravity dependent instability of two-layer Couette flows and its nonlinear saturationOct 16 2016A horizontal flow of two immiscible fluid layers with different densities, viscosities and thicknesses, subject to vertical gravitational forces and with an insoluble surfactant present at the interface, is investigated. The base Couette flow is driven ... More
Analytic Few Photon Scattering in Waveguide QEDMay 19 2017Apr 04 2018We develop an approach to light-matter coupling in waveguide QED based upon scattering amplitudes evaluated via Dyson series. For optical states containing more than single photons, terms in this series become increasingly complex and we provide a diagrammatic ... More
Quasilocal energy and thermodynamic equilibrium conditionsJun 18 2015Jul 30 2015Equilibrium thermodynamic laws are typically applied to horizons in general relativity without stating the conditions that bring them into equilibrium. We fill this gap by applying a new thermodynamic interpretation to a generalized Raychaudhuri equation ... More
Stable gravastars - an alternative to black holes?Oct 23 2003Dec 04 2003The "gravastar" picture developed by Mazur and Mottola is one of a very small number of serious challenges to our usual conception of a "black hole". In the gravastar picture there is effectively a phase transition at/ near where the event horizon would ... More
Partial regularity of mass-minimizing Cartesian currentsMar 28 2004Jul 17 2008Let B be a fiber bundle with compact fiber F over a compact Riemannian n-manifold M. There is a natural Riemannian metric on the total space B consistent with the metric on M. With respect to that metric, the volume of a rectifiable section s:M--> B is ... More
Variance Breakdown of Huber (M)-estimators: $n/p \rightarrow m \in (1,\infty)$Mar 06 2015A half century ago, Huber evaluated the minimax asymptotic variance in scalar location estimation, $ \min_\psi \max_{F \in {\cal F}_\epsilon} V(\psi, F) = \frac{1}{I(F_\epsilon^*)} $, where $V(\psi,F)$ denotes the asymptotic variance of the $(M)$-estimator ... More
Analytic approach for calculating transmitted electromagnetic fields through a slot array in deep sub-wavelength regimeJun 20 2011For the diffraction of an incident plane electromagnetic wave by a slotted metallic film, the previous analytical calculation for a single slot [Technical Phys. 50, 1076 (2005)] is generalized into a model for an arbitrary linear array of slots with variable ... More
A Natural 125 GeV Higgs Boson in the MSSM from Focus Point Supersymmetry with A-TermsMay 10 2012We show that a 125 GeV Higgs boson and percent-level fine-tuning are simultaneously attainable in the MSSM, with no additional fields and supersymmetry breaking generated at the GUT scale. The Higgs mass is raised by large radiative contributions from ... More
The IMP game: Learnability, approximability and adversarial learning beyond $Σ^0_1$Feb 07 2016We introduce a problem set-up we call the Iterated Matching Pennies (IMP) game and show that it is a powerful framework for the study of three problems: adversarial learnability, conventional (i.e., non-adversarial) learnability and approximability. Using ... More
Constraint Processing in Lifted Probabilistic InferenceMay 09 2012First-order probabilistic models combine representational power of first-order logic with graphical models. There is an ongoing effort to design lifted inference algorithms for first-order probabilistic models. We analyze lifted inference from the perspective ... More
Automorphism group of the moduli space of parabolic bundles over a curveMay 29 2019We find the automorphism group of the moduli space of parabolic bundles on a smooth curve (with fixed determinant and system of weights). This group is generated by: automorphisms of the marked curve, tensoring with a line bundle, taking the dual, and ... More
Temperature dependence of current self-oscillations and electric field domains in sequential tunneling doped superlatticesApr 06 2001We examine how the current--voltage characteristics of a doped weakly coupled superlattice depends on temperature. The drift velocity of a discrete drift model of sequential tunneling in a doped GaAs/AlAs superlattice is calculated as a function of temperature. ... More