Results for "R. G. Povey"

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Cryogenic resonant microwave cavity searches for hidden sector photonsOct 20 2014The hidden sector photon is a weakly interacting hypothetical particle with sub-eV mass that kinetically mixes with the photon. We describe a microwave frequency light shining through a wall experiment where a cryogenic resonant microwave cavity is used ... More
Comparison of ultra-stable radio frequency signals synthesized from independent secondary microwave frequency standardsFeb 01 2013The phase noise and frequency stability measurements of 1 GHz, 100 MHz, and 10 MHz signals are presented which have been synthesized from microwave cryogenic sapphire oscillators using ultra-low-vibration pulse-tube cryocooler technology. We present the ... More
Microwave cavity light shining through a wall optimization and experimentMar 04 2010Sep 02 2010It has been proposed that microwave cavities can be used in a photon regeneration experiment to search for hidden sector photons. Using two isolated cavities, the presence of hidden sector photons could be inferred from a 'light shining through a wall' ... More
Microwave cavity hidden sector photon threshold crossingMay 31 2011Hidden sector photons are a weakly interacting slim particle arising from an additional U(1) gauge symmetry predicted by many standard model extensions. We present and demonstrate a new experimental method using a single microwave cavity to search for ... More
A versatile scanning acoustic platformOct 13 2009Feb 01 2010We present a versatile and highly configurable scanning acoustic platform. This platform, comprising of a high frequency transducer, bespoke positioning system and temperature-regulated sample unit, enables the acoustic probing of materials over a wide ... More
A transposed frequency technique for phase noise and frequency stability measurementsAug 29 2012Nov 29 2012The digital signal processing has greatly simplified the process of phase noise measurements, especially in oscillators, but its applications are largely confined to the frequencies below 400 MHz. We propose a novel transpose frequency technique, which ... More
Violating Bell's inequality with remotely-connected superconducting qubitsAug 09 2018Oct 17 2018Quantum communication relies on the efficient generation of entanglement between remote quantum nodes, due to entanglement's key role in achieving and verifying secure communications. Remote entanglement has been realized using a number of different probabilistic ... More
Phonon-mediated quantum state transfer and remote qubit entanglementMar 13 2019Phonons, and in particular surface acoustic wave phonons, have been proposed as a means to coherently couple distant solid-state quantum systems. Recent experiments have shown that superconducting qubits can control and detect individual phonons in a ... More
Unidirectional Distributed Acoustic Reflection Transducers for Quantum ApplicationsMay 08 2019Recent significant advances in coupling superconducting qubits to acoustic wave resonators has led to demonstrations of quantum control of surface and bulk acoustic resonant modes as well Wigner tomography of quantum states in these modes. These advances ... More
Resonant Regeneration in the Sub-Quantum Regime -- A demonstration of fractional quantum interferenceJan 21 2011Light shining through wall experiments (in the optical as well as in the microwave regime) are a powerful tool to search for light particles coupled very weakly to photons such as axions or extra hidden sector photons. Resonant regeneration, where a resonant ... More
Post-processing of polymer foam tissue scaffolds with high power ultrasound: a route to increased pore interconnectivity, pore size and fluid transportFeb 18 2013We expose thick polymer foam tissue scaffolds to high power ultrasound and study its effect on the openness of the pore architecture and fluid transport through the scaffold. Our analysis is supported by measurements of fluid uptake during insonification ... More
Longitudinal acoustic properties of poly(lactic acid) and poly(lactic-co-glycolic acid)May 24 2010Acoustics offers rich possibilities for characterising and monitoring the biopolymer structures being employed in the field of biomedical engineering. Here we explore the rudimentary acoustic properties of two common biodegradable polymers poly(lactic ... More
A preliminary study of acoustic propagation in thick foam tissue scaffolds composed of poly(lactic-co-glycolic acid)Feb 26 2010The exclusive ability of acoustic waves to probe the structural, mechanical and fluidic properties of foams may offer novel approaches to characterise the porous scaffolds employed in tissue engineering. Motivated by this we conduct a preliminary investigation ... More
Krylov Subspace Descent for Deep LearningNov 18 2011In this paper, we propose a second order optimization method to learn models where both the dimensionality of the parameter space and the number of training samples is high. In our method, we construct on each iteration a Krylov subspace formed by the ... More
Quantum control of surface acoustic wave phononsApr 19 2018The superposition of quantum states is one of the hallmarks of quantum physics, and clear demonstrations of superposition have been achieved in a number of quantum systems. However, mechanical systems have remained a challenge, with only indirect demonstrations ... More
MUSAN: A Music, Speech, and Noise CorpusOct 28 2015This report introduces a new corpus of music, speech, and noise. This dataset is suitable for training models for voice activity detection (VAD) and music/speech discrimination. Our corpus is released under a flexible Creative Commons license. The dataset ... More
Parallel training of DNNs with Natural Gradient and Parameter AveragingOct 27 2014Jun 22 2015We describe the neural-network training framework used in the Kaldi speech recognition toolkit, which is geared towards training DNNs with large amounts of training data using multiple GPU-equipped or multi-core machines. In order to be as hardware-agnostic ... More
A GPU-based WFST Decoder with Exact Lattice GenerationApr 09 2018Jul 27 2018We describe initial work on an extension of the Kaldi toolkit that supports weighted finite-state transducer (WFST) decoding on Graphics Processing Units (GPUs). We implement token recombination as an atomic GPU operation in order to fully parallelize ... More
Lithographyically defined, room temperature low threshold subwavelength red-emitting hybrid plasmonic lasersDec 30 2016Hybrid plasmonic lasers provide deep subwavelength optical confinement, strongly enhanced light-matter interaction and together with nanoscale footprint promise new applications in optical communication, bio-sensing and photolithography. The subwavelength ... More
Movable algebraic singularities of second-order ordinary differential equationsApr 17 2008Any nonlinear equation of the form y''=\sum_{n=0}^N a_n(z)y^n has a (generally branched) solution with leading order behaviour proportional to (z-z_0)^{-2/(N-1)} about a point z_0, where the coefficients a_n are analytic at z_0 and a_N(z_0)\ne 0. We consider ... More
On the double radiative decay of B_s-meson $B\toγγ$Oct 13 1998B_s-meson double radiative decay $B \to \gamma\gamma$ is investigated in frame of supersymmetric extension of the standard model. The branching ratio is calculated. It is shown that for light Higgs particle and heigh $\tan\beta$ supersymmetric contribution ... More
Quark Model Description of Polarised Deep Inelastic Scattering and the prediction of $g_2$Jan 10 1996We show how the operator product expansion evaluated in the approximation of ignoring gluons leads to the covariant formulation of the quark parton model. We discuss the connection with other formulations and show how the free quark model prediction, ... More
The Two and Three Point One Loop FunctionsOct 08 1997In the present paper the two and three point functions which occur at the study of the various physical processes are considered. The investigation has dan in the framework of the perturbative theory at the one loop level. The general and asymptotic expressions ... More
Skyrmions and pentaquarks in the quark-hadron continuity perspectiveJun 02 2004Oct 14 2004We argue that in the color-flavor-locking (CFL) superconducting phase classical soliton solutions can exist, whose excitations should be interpreted as states formed by a quark (or an antiquark) and condensed diquarks. This finding extends the picture ... More
Analysis of deep inelastic scattering with $z$-dependent scaleApr 13 1999Evolution of the parton densities at NLO in $\alpha_S$ using $\tilde W^2 = Q^2 (1-z)/z$ instead of the usual $Q^2$ for the scale of the running coupling $\alpha_S$ is investigated. While this renormalisation scale change was originally proposed as the ... More
Phenomenology of Deep Inelastic Scattering Structure FunctionsJun 06 1997I review recent progress in analysing deep inelastic scattering structure functions in global analyses. The new ingredients are new data and attempts to incorporate heavy quarks consistently. A new way of including the resummation of large $\log 1/x$ ... More
Theory on the mechanism of site-specific DNA-protein interactions in the presence of trapsMay 31 2016The speed of site-specific binding of transcription factor (TFs) proteins with genomic DNA seems to be strongly retarded by the randomly occurring sequence traps. Traps are those DNA sequences sharing significant similarity with the original specific ... More
X-ray absorption in Active Galactic NucleiJan 04 2007We review some of the main physical and statistical properties of the X-ray absorber in AGNs. In particular, we review the distribution of the absorbing column density inferred from X-ray observations of various AGN samples. We discuss the location of ... More
Effect of coulomb long range interactions on the Mott transitionMar 11 1999We reconsider the Mott transition problem in the presence of long range Coulomb interactions. Using an extended DMFT, that sums an important class of diagrams absent in ordinary DMFT, we show that in the presence of Coulomb the Mott transition in two ... More
Anomalous magnetic moment of muon and L-violating Supersymmetric ModelsJul 26 2001We consider L-violating Supersymmetric Models to explain the recent muon $g_{\mu} -2$ deviation from the Standard Model. The order of trilinear L-violating couplings which we require also generate neutrino mass which is somewhat higher than expected unless ... More
Orbital Dynamics: The Origin of Anomalous Magnon Softening in Ferromagnetic ManganitesApr 22 1999Jun 03 1999We study the renormalization of magnons by charge and coupled orbital-lattice fluctuations in colossal magnetoresistance compounds. The model considered is an orbitally degenerate double-exchange system coupled to Jahn-Teller active phonons. The modulation ... More
Hadron-hadron and hadron-nuclei collisions at high energiesOct 27 2000Nov 15 2000A brief review is made of the present situation of hadron-hadron and hadron-nuclei total elastic and inelastic cross sections at high energies
On Interferometric Duality in Multibeam ExperimentsJan 07 2003Sep 02 2003We critically analyze the problem of formulating duality between fringe visibility and which-way information, in multibeam interference experiments. We show that the traditional notion of visibility is incompatible with any intuitive idea of complementarity, ... More
Complementarity, measurement and information in interference experimentsAug 05 2002Different criteria (Shannon's entropy, Bayes' average cost, Durr's normalized rms spread) have been introduced to measure the "which-way" information present in interference experiments where, due to non-orthogonality of the detector states, the path ... More
Infrared Effects and Bubble Propagation at the Electroweak Phase TransitionJun 15 1992Jun 16 1992We discuss aspects of poor infrared behaviour of the perturbation expansion for the effective potential of the Higgs mode near the electroweak phase transition, and enlarge on the discovery that higher order effects weaken the transition. In addition, ... More
Direct correlation functions of the Widom-Rowlinson modelAug 21 2003We calculate, through Monte Carlo numerical simulations, the partial total and direct correlation functions of the three dimensional symmetric Widom-Rowlinson mixture. We find that the differences between the partial direct correlation functions from ... More
Generating functionals, consistency, and uniqueness in the integral equation theory of liquidsApr 20 2003We discuss and illustrate through numerical examples the relations between generating functionals, thermodynamic consistency (in particular the virial-free energy one), and uniqueness of the solution, in the integral equation theory of liquids. We propose ... More
Generalized Van Cittert Zernike Theorem in Curved Spacetime - Some Astrophysical ApplicationsSep 03 1994The {\em Van Cittert Zernike} theorem consists of a simple relation between the measured coherence of the radiation and the characteristics of the emitting stochastic source. In the present work, an extension of the theorem to partially correlated sources ... More
Heavy Element Enrichment of a Jupiter-mass Protoplanet as a Function of Orbital LocationMar 11 2009We calculate heavy element enrichment in a Jupiter-mass protoplanet formed by disk instability at various radial distances from the star, considering different disk masses and surface density distributions. Although the available mass for accretion increases ... More
Photo-excited zero-resistance states in the GaAs/AlGaAs systemApr 08 2005The microwave-excited high mobility two-dimensional electron system exhibits, at liquid helium temperatures, vanishing resistance in the vicinity of $B = [4/(4j+1)] B_{f}$, where $B_{f} = 2\pi\textit{f}m^{*}/e$, m$^{*}$ is an effective mass, e is the ... More
Spin characterization and control over the regime of radiation-induced zero-resistance statesJul 06 2004Over the regime of the radiation-induced zero-resistance states and associated oscillatory magnetoresistance, we propose a low magnetic field analog of quantum-Hall-limit techniques for the electrical detection of electron spin- and nuclear magnetic- ... More
Progress in relativistic gravitational theory using the inverse scattering methodApr 23 2003The increasing interest in compact astrophysical objects (neutron stars, binaries, galactic black holes) has stimulated the search for rigorous methods, which allow a systematic general relativistic description of such objects. This paper is meant to ... More
Balanced Topological Field TheoriesAug 26 1996Nov 18 1996We describe a class of topological field theories called ``balanced topological field theories.'' These theories are associated to moduli problems with vanishing virtual dimension and calculate the Euler character of various moduli spaces. We show that ... More
The Dynamics of Star Stream GapsJul 07 2013When a massive object crosses a star stream velocity changes are induced both along and transverse to the stream which can lead to the development of a visible gap. For a stream narrow relative to its orbital radius the time of stream crossing is sufficiently ... More
Bulge Building with Mergers and WindsMar 24 1999The gravitational clustering hierarchy and dissipative gas processes are both involved in the formation of bulges. Here we present a simple empirical model in which bulge material is assembled via gravitational accretion of the visible companion galaxies. ... More
Force on slowly moving variable electric or magnetic dipoles in vacuoDec 06 2016The force on electric and magnetic dipoles moving in vacuo is discussed in the general case of time-variable non-uniform fields and time-variable dipole moments, to first order in v/c and neglecting radiation reaction. Emphasis is given to the symmetry ... More
Geodesic equations and their numerical solutions in geodetic and Cartesian coordinates on an oblate spheroidNov 28 2016The direct geodesic problem on an oblate spheroid is described as an initial value problem and is solved numerically in geodetic and Cartesian coordinates. The geodesic equations are formulated by means of the theory of differential geometry. The initial ... More
New type of magneto-rotational instability in cylindrical Taylor-Couette flowAug 01 2005We study the stability of cylindrical Taylor-Couette flow in the presence of combined axial and azimuthal magnetic fields, and show that adding an azimuthal field profoundly alters the previous results for purely axial fields. For small magnetic Prandtl ... More
Observations of Dissipation of Slow Magneto-acoustic Waves in a Polar Coronal HoleJul 03 2014Aug 11 2014We focus on a polar coronal hole region to find any evidence of dissipation of propagating slow magneto-acoustic waves. We obtained time-distance and frequency-distance maps along the plume structure in a polar coronal hole. We also obtained Fourier power ... More
Cluster Mergers, Radio Halos and Hard X-ray Tails: A Statistical Magneto-Turbulent ModelApr 26 2004There is now firm evidence that the ICM consists of a mixture of hot plasma, magnetic fields and relativistic particles. The most important evidences for non-thermal phenomena in galaxy clusters comes from the diffuse Mpc-scale synchrotron radio emission ... More
Unconventional SuperconductivityMay 16 2017May 29 2017Conventional superconductivity, as used in this review, refers to electron-phonon coupled superconducting electron-pairs described by BCS theory. Unconventional superconductivity refers to superconductors where the Cooper pairs are not bound together ... More
Superconductivity in the A15 StructureMay 24 2015The cubic A15 structure metals, with over 60 distinct member compounds, held the crown of highest Tc superconductor starting in 1954 with the discovery of Tc=18 K in Nb3Sn. Tc increased over the next 20 years until the discovery in 1973 of Tc = 22.3 K ... More
The Continuous Wavelet Transform and Symmetric SpacesNov 08 2001The continuous wavelet transform has become a widely used tool in applied science during the last decade. In this article we discuss some generalizations coming from actions of closed subgroups of $\mathrm{GL}(n,\mathbb{R})$ acting on $\mathbb{R}^n$. ... More
Anomalous differential conductance of In-Bi2Te3 contactMar 03 2011The differential conductance of In/Bi2Te3 contact under cryogenic temperature is investigated. Anomalous zero/finite bias differential conductance has been observed. The dependence of the observed anomalous differential conductance on magnetic field and ... More
Diophantine IntegrabilityApr 13 2005The heights of iterates of the discrete Painleve equations over number fields appear to grow no faster than polynomials while the heights of generic solutions of non-integrable discrete equations grow exponentially. This gives rise to a simple and effective ... More
Asymptotic scaling in a model class of anomalous reaction-diffusion equationsMay 05 2005We analyze asymptotic scaling properties of a model class of anomalous reaction-diffusion (ARD) equations. Numerical experiments show that solutions to these have, for large $t$, well defined scaling properties. We suggest a general framework to analyze ... More
Neutrino Mass and OscillationsJan 12 2000Jan 13 2000Current evidence for neutrino oscillation is reviewed, some areas for closer investigation are suggested, and a plausible future experimental program is summarized.
Relativistic Thomas-Fermi Model at Finite TemperaturesMay 09 2001We briefly review the Thomas-Fermi statistical model of atoms in the classical non-relativistic formulation and in the generalised finite-nucleus relativistic formulation. We then discuss the classical generalisation of the model to finite temperatures ... More
Effective action approach to strongly correlated fermion systemsNov 15 1999We construct a new functional for the single particle Green's function, which is a variant of the standard Baym Kadanoff functional. The stability of the stationary solutions to the new functional is directly related to aspects of the irreducible particle ... More
Orbital polarons in the metal-insulator transition of manganitesJun 03 1999The metal-insulator transition in manganites is strongly influenced by the concentration of holes present in the system. Based upon an orbitally degenerate Mott-Hubbard model we analyze two possible localization scenarios to account for this doping dependence: ... More
Orbital dynamics: The origin of the anomalous optical spectra in ferromagnetic manganitesOct 03 1998We discuss the role of orbital degeneracy in the transport properties of perovskite manganites, focusing in particular on the optical conductivity in the metallic ferromagnetic phase at low temperatures. Orbital degeneracy and strong correlations are ... More
Generating Functional for Strong and Nonleptonic Weak InteractionsJul 14 2005Oct 05 2005The generating functional for Green functions of quark currents is given in closed form to next-to-leading order in the low-energy expansion for chiral SU(3), including one-loop amplitudes with up to three meson propagators. Matrix elements and form factors ... More
Four-pion production in e+ e- annihilationMar 07 2002Jun 18 2002We calculate the processes e+ e- -> 4 pions and tau -> nu_tau + 4 pions to O(p^4) in the low-energy expansion of the standard model. The chiral amplitudes of O(p^4) can be extended via resonance exchange to energies around 1 GeV. Higher-order effects ... More
Cold Gas and Star Formation in Elliptical GalaxiesAug 24 1998Elliptical galaxies outside dense clusters are observed to contain small amounts (relative to spiral galaxies) of cold interstellar gas. This review discusses the atomic gas, the molecular gas, and the dust in elliptical galaxies. Field elliptical galaxies ... More
Interaction between an electric charge and a magnetic dipole of any kind (permanent, para- or dia- magnetic or superconducting)Jun 04 2015The interaction between point charge and magnetic dipole is usually considered only for the case of a rigid ferromagnetic dipole (constant-current): here the analysis of force, momentum and energy (including the energy provided by the internal current ... More
Customized Beam Forming at the Allen Telescope Array (August 11, 2002)Oct 28 2012Nov 27 2012One of the exciting prospects for large N arrays is the potential for custom beam forming when operating in phased array mode. Pattern nulls may be generated by properly weighting the signals from all antennas with only minor degradation of gain in the ... More
Critical light scattering in liquidsMar 20 2000We compare theoretical results for the characteristic frequency of the Rayleigh peak calculated in one-loop order within the field theoretical method of the renormalization group theory with experiments and other theoretical results. Our expressions describe ... More
Upper End IMF Variations Deduced from HI-Selected GalaxiesAug 24 2010Much of our understanding of modern astrophysics rest on the notion that the Initial Mass Function (IMF) is universal. Our observations of a sample of HI-selected galaxies in the light of H-alpha and the far-ultraviolet (FUV) challenge this result. The ... More
Dust in the High Redshift UniverseOct 14 2003This paper reviews the dust content of the high redshift (z > 2) universe. Studies of the various "species" in the high-z "zoo" show that almost all have strong evidence for containing dust. The one exception, where the evidence is not yet convincing, ... More
Quantifying Morphological Evolution from Low to High RedshiftsJun 12 2000Establishing the morphological history of ordinary galaxies was one of the original goals for the Hubble Space Telescope, and remarkable progress toward achieving this this goal has been made. How much of this progress has been at the expense of the Hubble ... More
Quantitative Morphology at High RedshiftsFeb 03 1998The current evidence for morphologically peculiar galaxy populations at high-redshifts is outlined. After describing various techniques which can be used to quantify the importance of ``morphological K-corrections'', and to objectively classify galaxy ... More
Flux Creep and Flux JumpingJul 02 1995We consider the flux jump instability of the Bean's critical state arising in the flux creep regime in type-II superconductors. We find the flux jump field, $B_j$, that determines the superconducting state stability criterion. We calculate the dependence ... More
The Monster's Fiery Breath and its Impact on Galaxy FormationSep 11 2009My aim in this talk is to make clear that there are two sides to galaxy formation: the properties of the galaxies themselves, and the properties of the material that is left over from the galaxy formation process. To date, galaxy formation studies have ... More
COMMENTS ABOUT HIGGS FIELDS, NONCOMMUTATIVE GEOMETRY AND THE STANDARD MODELMay 31 1995We make a short review of the formalism that describes Higgs and Yang Mills fields as two particular cases of an appropriate generalization of the notion of connection. We also comment about the several variants of this formalism, their interest, the ... More
Non-equilibrium critical dynamics in disordered ferromagnetsNov 23 2005We discuss some aspects of the non-equilibrium relaxational dynamics which occur after a quench at a disordered critical point. In particular, we focus on the violation of the fluctuation dissipation theorem for local as well as non-local observables ... More
RF power generationDec 14 2011This paper reviews the main types of r.f. power amplifiers which are, or may be, used for particle accelerators. It covers solid-state devices, tetrodes, inductive output tubes, klystrons, magnetrons, and gyrotrons with power outputs greater than 10 kW ... More
Type Ia supernovae in globular clusters: observational upper limitsNov 28 2011In the dense stellar environment of the globular clusters, compact binaries are produced dynamically. Therefore the fraction of type Ia supernovae that explode in globular clusters is expected to be higher than the fraction of mass residing in these. ... More
G_2^1 Affine Toda Field Theory: A Numerical Test of Exact S-Matrix resultsJun 30 1992We present the results of a Monte--Carlo simulation of the $G_2^{(1)}$ Affine Toda field theory action in two dimensions. We measured the ratio of the masses of the two fundamental particles as a function of the coupling constant. Our results strongly ... More
Universality in an Information-theoretic Motivated Nonlinear Schrodinger EquationJul 31 2006May 24 2007Using perturbative methods, we analyse a nonlinear generalisation of Schrodinger's equation that had previously been obtained through information-theoretic arguments. We obtain analytical expressions for the leading correction, in terms of the nonlinearity ... More
Variations of the spectral excess theorem for normal digraphsOct 28 2013It is known that every distance-regular digraph is connected and normal. An interesting question is: when is a given connected normal digraph distance-regular? Motivated by this question first we give some characterizations of weakly distance-regular ... More
Today's Cosmological ConstantsApr 29 1998Knowledge of the constants that describe the current cosmological world model, H_0, t_0, and the three Omega's is central to physical cosmology. Although there is a vast range of suggested tests and existing constraints much of the recent discussion of ... More
Effects of van-Hove singularities on the upper critical fieldOct 12 2000We present a study of the superconducting pairing susceptibility $K_T(r)$ for a two-dimensional isotropic system with a strong power-law divergence in the density of states $N(\epsilon) \sim \epsilon^{-1+\frac{1}{b}}$, $b>1$. We show that the pair propagator ... More
Solutions of Einstein's field equations related to Jacobi's inversion problemFeb 14 2003A new class of exact solutions to the axisymmetric and stationary vacuum Einstein equations containing n arbitrary complex parameters and one arbitrary real solution of the axisymmetric three-dimensional Laplace equation is presented. The solutions are ... More
The global atmospheric electrical circuit and climateJun 08 2005Evidence is emerging for physical links among clouds, global temperatures, the global atmospheric electrical circuit and cosmic ray ionisation. The global circuit extends throughout the atmosphere from the planetary surface to the lower layers of the ... More
Comment on "Helical MRI in magnetized Taylor-Couette flow"May 07 2007May 10 2007Liu et al. [Phys. Rev. E 74, 056302 (2006)] have presented a WKB analysis of the helical magnetorotational instability (HMRI), and claim that it does not exist for Keplerian rotation profiles. We show that if radial boundary conditions are included, the ... More
Swift highlights and flares (Back to the drawing board?)May 25 2010Swift opened up a new era in the study of gamma-ray burst sources (GRB). Among a variety of discoveries made possible by Swift, here we focus on GRB090423, the event at z=8.2 which currently holds the record of the most distant celestial object ever caught ... More
On the uniform generation of random derangementsSep 12 2018Sep 19 2018We show how to generate random derangements with the expected distribution of cycle lengths by two different techniques: random restricted transpositions and sequential importance sampling. The algorithms are simple to understand and implement and possess ... More
Enhancement of the helium resonance lines in the solar atmosphere by suprathermal electron excitation II: non-Maxwellian electron distributionsJun 20 2003In solar EUV spectra the He I and He II resonance lines show unusual behaviour and have anomalously high intensities compared with other transition region lines. The formation of the helium resonance lines is investigated through extensive non-LTE radiative ... More
Radiating Gravitational Collapse with an Initial Inhomogeneous Energy Density DistributionJun 01 2014A new model is proposed to a collapsing star consisting of an initial inhomogeneous energy density and anisotropic pressure fluid with shear, radial heat flow and outgoing radiation. In previous papers one of us has always assumed an initial star with ... More
Radiating Gravitational Collapse with Shearing Motion and Bulk Viscosity RevisitedJan 11 2013A new model is proposed to a collapsing star consisting of an anisotropic fluid with bulk viscosity, radial heat flow and outgoing radiation. In a previous paper one of us has introduced a function time dependent into the $g_{rr}$, besides the time dependent ... More
Quantum Gravity and Equivariant CohomologyJul 27 1994Aug 09 1994A procedure for obtaining correlation function densities and wavefunctionals for quantum gravity from the Donaldson polynomial invariants of topological quantum field theories, is given. We illustrate how our procedure may be applied to three and four ... More
Neutrino Oscillations and EntanglementApr 11 2010Jun 10 2010An improved treatment of neutrino oscillations follows when neutrino mass eigenstates and their associated recoiling particle states are entangled. When the neutrino and its recoil partner are treated as a single entangled quantum state the conservation ... More
Analysis and Extension of Omega-RuleApr 30 2009Mar 12 2011$\Omega$-rule was introduced by W. Buchholz to give an ordinal-free cut-elimination proof for a subsystem of analysis with $\Pi^{1}_{1}$-comprehension. His proof provides cut-free derivations by familiar rules only for arithmetical sequents. When second-order ... More
A Note on Set Graceful Labeling of GraphsJan 14 2011We settle affirmatively a conjecture posed in [S. M. Hegde, Set colorings of graphs, European Journal of Combinatorics 30 (4) (2009), 986--995]: If some subsets of a set X are assigned injectively to all vertices of a complete bipartite graph G such that ... More
Algorithm for calculating spectral intensity due to charged particles in arbitrary motionJun 03 2009Jun 04 2009An algorithm for calculating the spectral intensity of radiation due to the coherent addition of many particles with arbitrary trajectories is described. Direct numerical integration of the Lienard-Wiechert potentials, in the far-field, for extremely ... More
An alternative approach to viscosity in an accretion discSep 27 2006Oct 02 2006Purely hydrodynamic numerical experiments into the evolution of astrophysical discs typically include some sort of viscosity in order to cause accretion. In this paper, we demonstrate an alternative method of implementing viscous forces, with extremely ... More
Galois theory and a new homotopy double groupoid of a map of spacesAug 27 2002The authors have used generalised Galois Theory to construct a homotopy double groupoid of a surjective fibration of Kan simplicial sets. Here we apply this to construct a new homotopy double groupoid of a map of spaces, which includes constructions by ... More
Weakly Closed Unipotent Subgroups in Chevalley GroupsNov 17 2005Dec 19 2005The goal of this note is to classify the weakly closed unipotent subgroups in the split Chevalley groups. In an application we show under some mild assumptions on the characteristic that the Lie algebra of a connected simple algebraic group fails to be ... More
A Method of Classifying Simple Laced Root SystemsJun 12 2008A root system in which all roots have same norm is known as a simply laced root system. We present a simple method of classifying all simply laced root systems.
Spectra of Modular Random GraphsAug 21 2009We compute spectra of symmetric random matrices defined on graphs exhibiting a modular structure. Modules are initially introduced as fully connected sub-units of a graph. By contrast, inter-module connectivity is taken to be incomplete. Two different ... More