Results for "Oliver A Williams"

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Real time clustering of time series using triangular potentialsFeb 18 2015Motivated by the problem of computing investment portfolio weightings we investigate various methods of clustering as alternatives to traditional mean-variance approaches. Such methods can have significant benefits from a practical point of view since ... More
Localization of Large Polarons in the Disordered Holstein ModelMar 26 2014We solve the disordered Holstein model via the DMRG method to investigate the combined roles of electron-phonon coupling and disorder on the localization of a single charge or exciton. The parameter regimes chosen, namely the adiabatic regime, $\hbar\omega/4t_0 ... More
Is the deformation space of complete affine structures on the 2-torus smooth?Jan 20 2004Jun 14 2005Periods of parallel exterior forms define natural coordinates on the deformation space of complete affine structures on the two-torus. These coordinates define a differentiable structure on this deformation space, under which it is diffeomorphic to $R^2$. ... More
Polishing of {100} and {111} single crystal diamond through the use of Chemical Mechanical PolishingFeb 14 2014Diamond is one of the hardest and most difficult to polish materials. In this paper, the polishing of {111} and {100} single crystal diamond surfaces by standard Chemical Mechanical Polishing, as used in the silicon industry, is demonstrated. A Logitech ... More
Chemical mechanical polishing of thin film diamondAug 06 2013The demonstration that Nanocrystalline Diamond (NCD) can retain the superior Young's modulus (1,100 GPa) of single crystal diamond twinned with its ability to be grown at low temperatures (<450 {\deg}C) has driven a revival into the growth and applications ... More
A simple, space constrained NIRIM type reactor for chemical vapour deposition of diamondMar 26 2018In this paper the design of a simple, space constrained chemical vapour deposition reactor for diamond growth is detailed. Based on the design by NIRIM, the reactor is composed of a quartz discharge tube placed within a 2.45 GHz waveguide to create the ... More
Superconducting nano-mechanical diamond resonatorsJan 28 2014In this work we present the fabrication and characterization of superconducting nano-mechanical resonators made from nanocrystalline boron doped diamond (BDD). The oscillators can be driven and read out in their superconducting state and show quality ... More
Heisenberg-limited qubit readout with two-mode squeezed lightFeb 02 2015Aug 28 2015We show how to use two-mode squeezed light to exponentially enhance cavity-based dispersive qubit measurement. Our scheme enables true Heisenberg-limited scaling of the measurement, and crucially, is not restricted to small dispersive couplings or unrealistically ... More
A detailed analysis of the Raman spectra in superconducting boron doped nanocrystalline diamondApr 24 2012May 03 2013The light scattering properties of superconducting (Tc=3.8 K) heavily boron doped nanocrystalline diamond has been investigated by Raman spectroscopy using visible excitations. Fano type interference of the zone-center phonon line and the electronic continuum ... More
Degree correlations in directed scale-free networksSep 17 2014Scale-free networks, in which the distribution of the degrees obeys a power-law, are ubiquitous in the study of complex systems. One basic network property that relates to the structure of the links found is the degree assortativity, which is a measure ... More
Time-Reversal Symmetry and Universal Conductance Fluctuations in a Driven Two-Level SystemApr 28 2012In the presence of time-reversal symmetry, quantum interference gives strong corrections to the electric conductivity of disordered systems. The self-interference of an electron wavefunction traveling time-reversed paths leads to effects such as weak ... More
Electron Entanglement via a Quantum DotJul 16 2001This Letter presents a method of electron entanglement generation. The system under consideration is a single-level quantum dot with one input and two output leads. The leads are arranged such that the dot is empty, single electron tunneling is suppressed ... More
Effects of memory on spreading processes in non-Markovian temporal networksOct 09 2018Many biological, social and man-made systems are better described in terms of temporal networks, i.e. networks whose links are only present at certain points in time, rather than by static ones. In particular, it has been found that non-Markovianity is ... More
Quantifying and predicting success in show businessJan 05 2019Recent studies in the science of success have shown that the highest-impact works of scientists or artists happen randomly and uniformly over the individual's career. Yet in certain artistic endeavours, such as acting in films and TV, having a job is ... More
Superconducting Diamond on Silicon Nitride for Device ApplicationsOct 24 2018Chemical vapour deposition (CVD) grown nanocrystalline diamond is an attractive material for the fabrication of devices. For some device architectures, optimisation of its growth on silicon nitride is essential. Here, the effects of three pre-growth surface ... More
Production of Metal-free Diamond NanoparticlesAug 20 2018In this paper, the controlled production of high quality metal-free diamond nanoparticles is demonstrated. Milling with tempered steel is shown to leave behind iron oxide contamination which is difficult to remove. Milling with SiN alleviates this issue ... More
Fabrication Process and Properties of Fully-Planarized Deep-Submicron Nb/Al-AlOx/Nb Josephson Junctions for VLSI CircuitsAug 25 2014Dec 19 2014A fabrication process for Nb/Al-AlOx/Nb Josephson junctions (JJs) with sizes down to 200 nm has been developed on a 200-mm-wafer tool set typical for CMOS foundry. This process is the core of several nodes of a roadmap for fully-planarized fabrication ... More
Battery-like Supercapacitors from Vertically Aligned Carbon Nanofibers Coated Diamond: Design and DemonstratorJan 26 2018Battery-like supercapacitors feature high power and energy densities as well as long-term capacitance retention. The utilized capacitor electrodes are thus better to have large surface areas, high conductivity, high stability, and importantly be of binder ... More
Quantitative analysis of the interaction between a dc SQUID and an integrated micromechanical doubly clamped cantileverFeb 08 2019Based on the superconducting quantum interference device (SQUID) equations described by the resistively- and capacitively-shunted junction model coupled to the equation of motion of a damped harmonic oscillator, we provide simulations to quantitatively ... More
Nanostructures made from superconducting boron doped diamondMar 05 2010Mar 30 2010We report on the transport properties of nanostructures made from boron-doped superconducting diamond. Starting from nanocrystalline superconducting boron-doped diamond thin films, grown by Chemical Vapor Deposition, we pattern by electron-beam lithography ... More
Redox agent enhanced chemical mechanical polishing of thin film diamondJan 02 2018The chemical nature of the chemical mechanical polishing of diamond has been examined by adding various redox agents to the alkaline SF1 polishing slurry. Three oxidizing agents namely, hydrogen peroxide, potassium permanganate and ferric nitrate, and ... More
A Conceptual Shift to Rectify a Defect in the Lorentz-Dirac EquationJun 04 2013In his analysis of the Classical Theory of Radiating Electrons, Dirac (1938) draws attention to the characteristic instability of solutions to the third order equation of motion. He remarks that changing the sign of the self-force eliminates the runaway ... More
Surface zeta potential and diamond seeding on gallium nitride filmsJul 17 2017Oct 09 2017Measurement of zeta potential of Ga and N-face gallium nitride has been carried out as function of pH. Both the faces show negative zeta potential in the pH range 5.5-9. The Ga face has an isoelectric point at pH 5.5. The N-face shows higher negative ... More
Doppelgängers: Bijections of Plane PartitionsFeb 17 2016Sep 29 2016We say two posets are "doppelg\"angers" if they have the same number of $P$-partitions of each height $k$. We give a uniform framework for bijective proofs that posets are doppelg\"angers by synthesizing $K$-theoretic Schubert calculus techniques of H. ... More
To Drop or Not to Drop: Robustness, Consistency and Differential Privacy Properties of DropoutMar 06 2015Training deep belief networks (DBNs) requires optimizing a non-convex function with an extremely large number of parameters. Naturally, existing gradient descent (GD) based methods are prone to arbitrarily poor local minima. In this paper, we rigorously ... More
FIM tips in SPM: Apex orientation and temperature considerations on atom transfer and diffusionAug 03 2013Atoms transferred to W(111) and W(110) tip apices from the Au(111) surface during tunneling and approach to mechanical contact experiments in STM are characterized in FIM at room temperature and at 158 K. The different activation energies for diffusion ... More
Efficient, adaptive cross-validation for tuning and comparing models, with application to drug discoveryFeb 29 2012Cross-validation (CV) is widely used for tuning a model with respect to user-selected parameters and for selecting a "best" model. For example, the method of $k$-nearest neighbors requires the user to choose $k$, the number of neighbors, and a neural ... More
Dirac Neutrinos and Hybrid Inflation from String TheoryMay 16 2005Jun 15 2005We consider a possible scenario for the generation of Dirac neutrino masses motivated by Type I string theory. The smallness of the neutrino Yukawa couplings is explained by an anisotropic compactification with one compactification radius larger than ... More
Transient adhesion and conductance phenomena in initial nanoscale mechanical contacts between dissimilar metalsAug 05 2013Aug 07 2013We report on transient adhesion and conductance phenomena associated with tip wetting in mechanical contacts produced by the indentation of a clean W(111) tip into a Au(111) surface. A combination of atomic force microscopy and scanning tunneling microscopy ... More
Eigenvalues of sample covariance matrices of non-linear processes with infinite varianceNov 26 2012Sep 11 2013We study the $k$-largest eigenvalues of heavy-tailed sample covariance matrices of the form $\bX\bX^\T$ in an asymptotic framework, where the dimension of the data and the sample size tend to infinity. To this end, we assume that the rows of $\bX$ are ... More
Transit and Eclipse Analyses of Exoplanet HD 149026b Using BLISS MappingAug 09 2011May 25 2012The dayside of HD 149026b is near the edge of detectability by the Spitzer Space Telescope. We report on eleven secondary-eclipse events at 3.6, 4.5, 3 x 5.8, 4 x 8.0, and 2 x 16 microns plus three primary-transit events at 8.0 microns. The eclipse depths ... More
The Diamond SQUIDOct 01 2011Diamond is an electrical insulator in its natural form. However, when doped with boron above a critical level (~0.25 at.%) it can be rendered superconducting at low temperatures with high critical fields. Here we present the realization of a micrometer ... More
Observation of conduction electron spin resonance in boron doped diamondMay 10 2013We observe the electron spin resonance of conduction electrons in boron doped (6400 ppm) superconducting diamond (Tc =3.8 K). We clearly identify the benchmarks of conduction electron spin resonance (CESR): the nearly temperature independent ESR signal ... More
On Lyapunov-Krasovskii Functionals for Switched Nonlinear Systems with DelayNov 19 2013We present a set of results concerning the existence of Lyapunov-Krasovskii functionals for classes of nonlinear switched systems with time-delay. In particular, we first present a result for positive systems that relaxes conditions recently described ... More
Estimating the Number of Essential Genes in Random Transposon Mutagenesis LibrariesAug 03 2006Biologists use random transposon mutagenesis to construct knockout libraries for bacteria. Random mutagenesis offers cost and efficiency benefits over the standard site directed mutagenesis, but one can no longer ensure that all the nonessential genes ... More
Distillation of GHZ states by selective information manipulationJan 23 2000Feb 02 2000Methods for distilling maximally entangled tripartite (GHZ) states from arbitrary entangled tripartite pure states are described. These techniques work for virtually any input state. Each technique has two stages which we call primary and secondary distillation. ... More
Parametrization and distillability of three-qubit entanglementMay 29 2000Feb 02 2001There is an ongoing effort to quantify entanglement of quantum pure states for systems with more than two subsystems. We consider three approaches to this problem for three-qubit states: choosing a basis which puts the state into a standard form, enumerating ... More
On Constructing Persistent Identifiers with Persistent Resolution TargetsAug 30 2016Persistent Identifiers (PID) are the foundation referencing digital assets in scientific publications, books, and digital repositories. In its realization, PIDs contain metadata and resolving targets in form of URLs that point to data sets located on ... More
Efficient Finite Groups Arising in the Study of Relative AsphericityJul 07 2016We study a class of two-generator two-relator groups, denoted $J_n(m,k)$, that arise in the study of relative asphericity as groups satisfying a transitional curvature condition. Particular instances of these groups occur in the literature as finite groups ... More
Sub-micrometer epitaxial Josephson junctions for quantum circuitsAug 08 2011Nov 22 2011We present a fabrication scheme and testing results for epitaxial sub-micrometer Josephson junctions. The junctions are made using a high-temperature (1170 K) "via process" yielding junctions as small as 0.8 mu m in diameter by use of optical lithography. ... More
Reduced fusion systems over $p$-groups with abelian subgroup of index $p$: IIJun 16 2016Let $p$ be an odd prime, and let $S$ be a $p$-group with a unique elementary abelian subgroup $A$ of index $p$. We classify the simple fusion systems over all such groups $S$ in which $A$ is essential. The resulting list, which depends on the classification ... More
Power Markets for Controlling Smart MatterMar 07 1997Embedding microscopic sensors, computers and actuators into materials allows physical systems to actively monitor and respond to their environments. This leads to the possibility of creating smart matter, i.e., materials whose properties can be changed ... More
Power corrections in models with extra dimensionsOct 07 2003We critically revisit the issue of power-law running in models with extra dimensions. The general conclusion is that, in the absence of any additional physical principle, the power-corrections tend to depend strongly on the details of the underlying theory. ... More
Testing outer boundary treatments for the Einstein equationsApr 05 2007Jul 25 2007Various methods of treating outer boundaries in numerical relativity are compared using a simple test problem: a Schwarzschild black hole with an outgoing gravitational wave perturbation. Numerical solutions computed using different boundary treatments ... More
Can power corrections be reliably computed in models with extra dimensions?Feb 11 2003We critically revisit the issue of power-law running in models with extra dimensions. The analysis is carried out in the context of a higher-dimensional extension of QED, with the extra dimensions compactified on a torus. It is shown that a naive $\beta$ ... More
Reduced fusion systems over $p$-groups with abelian subgroup of index $p$: IIJun 16 2016Jul 21 2017Let $p$ be an odd prime, and let $S$ be a $p$-group with a unique elementary abelian subgroup $A$ of index $p$. We classify the simple fusion systems over all such groups $S$ in which $A$ is essential. The resulting list, which depends on the classification ... More
Quantum MulticriticalityJun 09 2015Several quantum critical compounds have been argued to have multiple instabilities towards orders with distinct dynamical exponents. We present an analysis of a quantum multicritical point in an itinerant magnet with competition between ferro- and antiferromagnetic ... More
Bounds on models with one latticized extra dimensionJun 30 2003We study an extension of the standard model with one latticized extra dimension accessible to all fields. The model is characterized by the size of the extra dimension and the number of sites, and contains a tower of massive particles. At energies lower ... More
Universal extra dimensions and Z->b bar-bDec 30 2002We study, at the one loop level, the dominant contributions from a single universal extra dimension to the process (Z\to b\bar{b}). By resorting to the gaugeless limit of the theory we explain why the result is expected to display a strong dependence ... More
B Physics and Extra DimensionsSep 03 2002We compute the dominant new physics contributions to the processes Z -> b b and B - B in the context of two representative models with extra dimensions. The main thrust of the calculations focuses on how to control the effects of the infinite tower of ... More
Limit Theory for the largest eigenvalues of sample covariance matrices with heavy-tailsAug 27 2011Oct 29 2012We study the joint limit distribution of the $k$ largest eigenvalues of a $p\times p$ sample covariance matrix $XX^\T$ based on a large $p\times n$ matrix $X$. The rows of $X$ are given by independent copies of a linear process, $X_{it}=\sum_j c_j Z_{i,t-j}$, ... More
Single microwave-photon detector using an artificial $Λ$-type three-level systemJan 21 2016Single photon detection is a requisite technique in quantum-optics experiments in both the optical and the microwave domains. However, the energy of microwave quanta are four to five orders of magnitude less than their optical counterpart, making the ... More
Resonant Readout of a Persistent Current QubitJan 12 2005We have implemented a resonant circuit that uses a SQUID as a flux-sensitive Josephson inductor for qubit readout. In contrast to the conventional switching current measurement that generates undesired quasi-particles when the SQUID switches to the voltage ... More
Nonlinear resonant behavior of the dispersive readout scheme for a superconducting flux qubitSep 22 2006A nonlinear resonant circuit comprising a SQUID magnetometer and a parallel capacitor is studied as a readout scheme for a persistent-current (PC) qubit. The flux state of the qubit is detected as a change in the Josephson inductance of the SQUID magnetometer, ... More
On Han's Hook Length Formulas for TreesMar 21 2011Recently, Han obtained two hook length formulas for binary trees and asked for combinatorial proofs. One of Han's formulas has been generalized to k-ary trees by Yang. Sagan has found a probabilistic proof of Yang's extension. We give combinatorial proofs ... More
HiggsBounds 2.0.0: Confronting Neutral and Charged Higgs Sector Predictions with Exclusion Bounds from LEP and the TevatronFeb 09 2011HiggsBounds 2.0.0 is a computer code which tests both neutral and charged Higgs sectors of arbitrary models against the current exclusion bounds from the Higgs searches at LEP and the Tevatron. As input, it requires a selection of model predictions, such ... More
Electronic coherence theoryDec 21 2003Sep 27 2004We withdraw our paper as the factorizability of the correlation functions is unproven.
QCD, Gauge Fixing, and the Gribov ProblemFeb 07 2002The standard techniques of gauge-fixing, such as covariant gauge fixing, are entirely adequate for the purposes of studies of perturbative QCD. However, they fail in the nonperturbative regime due to the presence of Gribov copies. These copies arise because ... More
A New Look at the Empirical Initial-Final Mass RelationOct 09 2006Oct 10 2006We examine new methods of producing and analyzing the empirical initial-final mass relation for open cluster white dwarfs (WDs). We re-determine initial and final masses for the complete sample of published cluster WDs and then pare this sample using ... More
Serendipitous discovery of a cluster of galaxies with a peculiar central galaxyApr 09 2001We report the serendipitous discovery of a cluster of galaxies at z=0.369. Thirty-eight candidate members were identified based on rough broad-band photometric redshifts, and three members were confirmed spectroscopically. The brightest cluster galaxy ... More
Vortex Fluctuations in the Critical Casimir Effect of Superfluid and Superconducting FilmsJul 05 2003Jul 10 2003Vortex-loop renormalization techniques are used to calculate the magnitude of the critical Casimir forces in superfluid films. The force is found to become appreciable when size of the thermal vortex loops is comparable to the film thickness, and the ... More
LHC Predictions from an extended theory with Elastic, Inelastic, and Path Length Fluctuating Energy LossFeb 27 2007We present the LHC predictions for the WHDG model of radiative, elastic, and path length fluctuating energy loss. We find the pT dependence of RAA is qualitatively very different from AWS-based energy loss extrapolations to the LHC; the large pT reach ... More
Aspherical Relative Presentations All Over AgainSep 10 2018Nov 21 2018The concept of asphericity for relative group presentations was introduced twenty five years ago. Since then, the subject has advanced and detailed asphericity classifications have been obtained for various families of one-relator relative presentations. ... More
Noise correlations in a flux qubit with tunable tunnel couplingApr 27 2011May 10 2011We have measured flux-noise correlations in a tunable superconducting flux qubit. The device consists of two loops that independently control the qubit's energy splitting and tunnel coupling. Low frequency flux noise in the loops causes fluctuations of ... More
Flux qubit noise spectroscopy using Rabi oscillations under strong driving conditionsFeb 06 2014We infer the high-frequency flux noise spectrum in a superconducting flux qubit by studying the decay of Rabi oscillations under strong driving conditions. The large anharmonicity of the qubit and its strong inductive coupling to a microwave line enabled ... More
Hook Length Formulas for Trees by Han's ExpansionMar 19 2009Recently Han obtained a general formula for the weight function corresponding to the expansion of a generating function in terms of hook lengths of binary trees. In this paper, we present formulas for k-ary trees, plane trees, plane forests, labeled trees ... More
Introducing HiggsBounds 2.0.0Dec 23 2010Jan 12 2011We introduce version 2.0.0 of the computer program HiggsBounds. The program tests neutral and charged Higgs sectors of new models against the current exclusion bounds from LEP and the Tevatron. As input, it requires a selection of model predictions, such ... More
Unions of Cockroft two-complexesOct 12 1993A combinatorial group-theoretic hypothesis is presented that serves as a necessary and sufficient condition for a union of connected Cockcroft two-complexes to be Cockcroft. This hypothesis has a component that can be expressed in terms of the second ... More
Comment on "Vortex String Formation in a 3D U(1) Temperature Quench"Apr 30 2014May 23 2014Comment on "Vortex String Formation in a 3D U(1) Temperature Quench" by N. D. Antunes, L. M. A. Bettencourt, and W. H. Zurek, Phys. Rev. Lett. 82, 2824 (1999).
Vortex Loop Phase Transitions in Liquid Helium, Cosmic Strings, and High-T_c SuperconductorsJul 25 1998Jan 18 1999The distribution of thermally excited vortex loops near a superfluid phase transition is calculated from a renormalized theory. The number density of loops with a given perimeter is found to change from exponential decay with increasing perimeter to algebraic ... More
CP Violation in Charged Higgs ProductionMay 13 2005I present a study estimating the amount of CP violation present in the production of charged Higgs bosons due to the presence of complex trilinear scalar couplings. I compare the results of my study with previous results for the decay. I briefly comment ... More
The impact of unresolved binaries on searches for white dwarfs in open clustersOct 15 2003Many open clusters have a deficit of observed white dwarfs (WDs) compared with predictions of the number of stars to have evolved into WDs. We evaluate the number of WDs produced in open clusters and the number of those WDS detectable using photometric ... More
Electromagnetically induced transparency in superconducting quantum circuits : Effects of decoherence, tunneling and multi-level cross-talkApr 04 2006We explore theoretically electromagnetically-induced transparency (EIT) in a superconducting quantum circuit (SQC). The system is a persistent-current flux qubit biased in a $\Lambda$ configuration. Previously [Phys. Rev. Lett. 93, 087003 (2004)], we ... More
NILMTK: An Open Source Toolkit for Non-intrusive Load MonitoringApr 15 2014Non-intrusive load monitoring, or energy disaggregation, aims to separate household energy consumption data collected from a single point of measurement into appliance-level consumption data. In recent years, the field has rapidly expanded due to increased ... More
Recent Developments in HiggsBounds and a Preview of HiggsSignalsJan 10 2013We report on recent developments in the public computer code HiggsBounds, which confronts arbitrary Higgs sector predictions with 95% C.L. exclusion limits from Higgs searches at the LEP, Tevatron and LHC experiments. We discuss in detail the performance ... More
HiggsBounds: Confronting Arbitrary Higgs Sectors with Exclusion Bounds from LEP and the TevatronNov 25 2008May 11 2011HiggsBounds is a computer code that tests theoretical predictions of models with arbitrary Higgs sectors against the exclusion bounds obtained from the Higgs searches at LEP and the Tevatron. The included experimental information comprises exclusion bounds ... More
Study of loss in superconducting coplanar waveguide resonatorsOct 28 2010Jan 04 2011Superconducting coplanar waveguide (SCPW) resonators have a wide range of applications due to the combination of their planar geometry and high quality factors relative to normal metals. However, their performance is sensitive to both the details of their ... More
Demo Abstract: NILMTK v0.2: A Non-intrusive Load Monitoring Toolkit for Large Scale Data SetsSep 20 2014Nov 09 2014In this demonstration, we present an open source toolkit for evaluating non-intrusive load monitoring research; a field which aims to disaggregate a household's total electricity consumption into individual appliances. The toolkit contains: a number of ... More
HiggsBounds-4: Improved Tests of Extended Higgs Sectors against Exclusion Bounds from LEP, the Tevatron and the LHCOct 31 2013We describe the new developments in version 4 of the public computer code HiggsBounds. HiggsBounds is a tool to test models with arbitrary Higgs sectors, containing both neutral and charged Higgs bosons, against the published exclusion bounds from Higgs ... More
Social interactions dominate speed control in driving natural flocks toward criticalityJul 21 2013Flocks of birds exhibit a remarkable degree of coordination and collective response. It is not just that thousands of individuals fly, on average, in the same direction and at the same speed, but that even the fluctuations around the mean velocity are ... More
Dynamical decoupling and dephasing in interacting two-level systemsApr 28 2012We implement dynamical decoupling techniques to mitigate noise and enhance the lifetime of an entangled state that is formed in a superconducting flux qubit coupled to a microscopic two-level system. By rapidly changing the qubit's transition frequency ... More
q-Hook Length Formulas for Signed Labeled ForestsApr 11 2010Apr 13 2010A signed labeled forest is defined as a (plane) forest labeled by {1,2,..., n} along with minus signs associated to some vertices. Signed labeled forests can be viewed as an extension of signed permutations. We define the inversion number, the flag major ... More
Tomonaga-Luttinger Liquid Features in Ballistic Single-Walled Carbon Nanotubes: Conductance and Shot NoiseOct 07 2006We study the electrical transport properties of well-contacted ballistic single-walled carbon nanotubes in a three-terminal configuration at low temperatures. We observe signatures of strong electron-electron interactions: the conductance exhibits bias-voltage-dependent ... More
On Shift Dynamics For Cyclically Presented GroupsDec 19 2013For group presentations with cyclic symmetry, there is a connection between asphericity and the dynamics of the shift automorphism. For the class of groups $G_n(k,l)$ described by the cyclic presentations $\mathcal{P}_n(k,l) = (x_i:x_ix_{i+k}x_{i+l}\ ... More
Finite-frequency dynamics of vortex loops at the $^4$He superfluid phase transitionOct 31 2008The finite-frequency dynamics of the $^4$He superfluid phase transition can be formulated in terms of the response of thermally excited vortex loops to an oscillating flow field. The key parameter is the Hausdorff fractal dimension $d_H$ of the loops, ... More
New results in vector meson dominance and rho meson physicsDec 17 1997Dec 24 1997Recent results by Benayoun et al. comparing the predictions of a range of existing models based on the Vector Meson Dominance hypothesis are summarized and discussed. These are compared with data on e+ e- -> pi+ pi- and e+ e- -> mu+ mu- cross-sections ... More
The Dynamics of Merging Clusters: A Monte Carlo Solution Applied to the Bullet and Musket Ball ClustersSep 28 2012Jul 21 2013Merging galaxy clusters have become one of the most important probes of dark matter, providing evidence for dark matter over modified gravity and even constraints on the dark matter self-interaction cross-section. To properly constrain the dark matter ... More
Anisotropic Kosterlitz-Thouless Transition Induced by Hard-Wall BoundariesMay 15 2006The spatial dependence of the superfluid density is calculated for the Kosterlitz-Thouless transition in the presence of hard-wall boundaries, for the case of a single wall bounding the half-infinite plane, and for a superfluid strip bounded by two walls. ... More
Lattice calculation of the gluon propagator and the strangeness magnetic moment of the nucleonSep 01 1998This contribution summarizes a presentation combining two topics in lattice QCD. Firstly, the gluon propagator in Landau gauge is calculated in quenched QCD on a large (32^3x64) lattice at beta=6.0. New structure seen in the infrared region survives conservative ... More
The Fermi GBM gamma-ray burst time-resolved spectral catalog: brightest bursts in the first four yearsJan 20 2016We aim to obtain high-quality time-resolved spectral fits of gamma-ray bursts (GRBs) observed by the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope. We perform time-resolved spectral analysis with high temporal and spectral ... More
A Stochastic Finite Element Model for the Dynamics of Globular MacromoleculesSep 21 2012We describe a novel coarse-grained simulation method for modelling the dynamics of globular macromolecules, such as proteins. The macromolecule is treated as a continuum that is subject to thermal fluctuations. The model includes a non-linear treatment ... More
Lattice study of the Kink soliton and the zero-mode problem for phi4 in two dimensionsNov 02 1998Nov 04 1998We study the $\lambda\phi^4_{1+1}$ kink solion and the zero-mode contribution to the Kink soliton mass in regions beyond the semiclassical regime. The calculations are done in the non-trivial scaling region and where appropriate the results are compared ... More
Pion Form Factors at Intermediate Momentum Transfer in a Covariant ApproachSep 16 1993We study the pion electromagnetic and $\gamma^* + \pi^0 \to \gamma$ transition form factors at intermediate momentum transfer. We calculate soft, nonperturbative corrections to the leading perturbative amplitudes which arise from the $q\bar q$-component ... More
Optimization of Monte-Carlo calculations of the effective potentialMay 16 1997We study Monte Carlo calculations of the effective potential for a scalar field theory using three techniques. One of these is a new method proposed and tested for the first time. In each case we extract the renormalised quantities of the theory. The ... More
Modeling of Lead Halide Perovskites for Photovoltaic ApplicationsMay 07 2014May 21 2014We report first-principles calculations, using the full potential linear augmented plane wave method, on six lead halide semiconductors, namely, CH3NH3PbI3, CH3NH3PbBr3, CsPbX3 (X=Cl, Br, I), and RbPbI3. Exchange is modeled using the modified Becke-Johnson ... More
Numerical Simulations of Magnetoacoustic-Gravity Waves in the Solar AtmosphereAug 29 2012We investigate the excitation of magnetoacoustic-gravity waves generated from localized pulses in the gas pressure as well as in vertical component of velocity. These pulses are initially launched at the top of the solar photosphere that is permeated ... More
Improving quantum gate fidelities by using a qubit to measure microwave pulse distortionsNov 09 2012We present a new method for determining pulse imperfections and improving the single-gate fidelity in a superconducting qubit. By applying consecutive positive and negative $\pi$ pulses, we amplify the qubit evolution due to microwave pulse distortion, ... More
Strongly inhomogeneous distribution of spectral properties of silicon-vacancy color centers in nanodiamondsJul 10 2018The silicon-vacancy (SiV) color center in diamond is a solid-state single photon emitter and spin quantum bit suited as a component in quantum devices. Here, we show that the SiV center in nanodiamond exhibits a strongly inhomogeneous distribution with ... More
Relation between Light Cone Distribution Amplitudes and Shape Function in B mesonsJul 20 2007Jan 29 2008The Bakamjian-Thomas relativistic quark model provides a Poincar\'e representation of bound states with a fixed number of constituents and, in the heavy quark limit, form factors of currents satisfy covariance and Isgur-Wise scaling. We compute the Light ... More
Lagrangian perturbations at order 1/m$_{\bf Q}$ and the non-forward amplitude in Heavy Quark Effective TheoryOct 13 2005We pursue the program of the study of the non-forward amplitude in HQET. We obtain new sum rules involving the elastic subleading form factors $\chi_i(w)$ $(i = 1,2, 3)$ at order $1/m_Q$ that originate from the ${\cal L}_{kin}$ and ${\cal L}_{mag}$ perturbations ... More