Results for "Ronan M. Kerr"

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Two radio-emission mechanisms in PSR J0901-4624Mar 15 2015We have detected sporadic, bright, short-duration radio pulses from PSR J0901$-$4624. These pulses are emitted simultaneously with persistent, periodic emission that dominates the flux density when averaging over many periods of the pulsar. The bright ... More
Broadband Phonon Scattering in PbTe-based Materials Driven Near the Ferroelectric Phase Transition by Strain or AlloyingMar 22 2019The major obstacle in the design of materials with low lattice thermal conductivity is the difficulty in efficiently scattering phonons across the entire frequency spectrum. Using first principles calculations, we show that driving PbTe materials to the ... More
Local well-posedness of the two-layer shallow water model with free surfaceFeb 13 2014In this paper, we adress the question of the hyperbolicity and the local well-posedness of the two-layer shallow water model, with free surface, in two dimensions. We first provide a general criterion that proves the symmetrizability of this model, which ... More
Local well-posedness of the multi-layer shallow-water model with free surfaceNov 10 2014Nov 29 2014In this paper, we address the question of the hyperbolicity and the local well- posedness of the multi-layer shallow water model, with free surface, in two dimensions. We first provide a general criterion that proves the symmetrizability of this model, ... More
Improved Query Topic Models via Pseudo-Relevant Pólya Document ModelsFeb 04 2016Query-expansion via pseudo-relevance feedback is a popular method of overcoming the problem of vocabulary mismatch and of increasing average retrieval effectiveness. In this paper, we develop a new method that estimates a query topic model from a set ... More
Central Exclusive Production at LHCbAug 29 2016Central Exclusive Production (CEP) is a unique process at hadron machines in which particles are produced via colourless propagators. LHCb have measured the cross-sections for the CEP of vector mesons, $J/\psi,\psi(2S),\Upsilon(1S),\Upsilon(2S)$ and $\Upsilon(3S)$, ... More
PRED18: Dataset and Further Experiments with DAVIS Event Camera in Predator-Prey Robot ChasingJul 02 2018Machine vision systems using convolutional neural networks (CNNs) for robotic applications are increasingly being developed. Conventional vision CNNs are driven by camera frames at constant sample rate, thus achieving a fixed latency and power consumption ... More
Characterising the rotational irregularities of the Vela pulsar from 21 yr of phase-coherent timingApr 10 2016Pulsars show two classes of rotational irregularities that can be used to understand neutron-star interiors and magnetospheres: glitches and timing noise. Here we present an analysis of the Vela pulsar spanning nearly 21 yr of observation and including ... More
A Massive Magnetic Helium Atmosphere White Dwarf Binary in a Young Star ClusterJun 11 2019We have searched the Gaia DR2 catalogue for previously unknown hot white dwarfs in the direction of young open star clusters. The aim of this experiment was to try and extend the initial-final mass relation (IFMR) to somewhat higher masses, potentially ... More
Critical Rayleigh number of for error function temperature profile with a quasi-static assumptionSep 16 2016Sep 20 2016When a semi-infinite body is heated from below by a sudden increase in temperature (or cooled from above) an error function temperature profile grows as the heat diffuses into the fluid. The stability of such a profile is investigated using a large-wavelength ... More
Boundary Components of Mumford-Tate DomainsOct 19 2012Apr 08 2015We study certain spaces of nilpotent orbits in Hodge domains, and treat a number of examples. More precisely, we compute the Mumford-Tate group of the limit mixed Hodge structure of a generic such orbit. The result is used to present these spaces as iteratively ... More
Modeling the non-recycled Fermi gamma-ray pulsar populationSep 08 2013We use Fermi Gamma-ray Space Telescope detections and upper limits on non-recycled pulsars obtained from the Large Area Telescope (LAT) to constrain how the gamma-ray luminosity L depends on the period P and the period derivative \dot{P}. We use a Bayesian ... More
A single-photon detector with high efficiency and sub-10ps time resolutionJan 19 2018The observation of fast physical dynamics using optical techniques currently relies on indirect methods, such as pump-probe measurements. One reason for this is the lack of an efficient detector with high time resolution. Single-photon detectors with ... More
Timing of young radio pulsars I: Timing noise, periodic modulation and proper motionAug 29 2019The smooth spin-down of young pulsars is perturbed by two non-deterministic phenomenon, glitches and timing noise. Although the timing noise provides insights into nuclear and plasma physics at extreme densities, it acts as a barrier to high-precision ... More
Who Needs Words? Lexicon-Free Speech RecognitionApr 09 2019Sep 13 2019Lexicon-free speech recognition naturally deals with the problem of out-of-vocabulary (OOV) words. In this paper, we show that character-based language models (LM) can perform as well as word-based LMs for speech recognition, in word error rates (WER), ... More
Estimating Phoneme Class Conditional Probabilities from Raw Speech Signal using Convolutional Neural NetworksApr 03 2013Jun 12 2013In hybrid hidden Markov model/artificial neural networks (HMM/ANN) automatic speech recognition (ASR) system, the phoneme class conditional probabilities are estimated by first extracting acoustic features from the speech signal based on prior knowledge ... More
End-to-end Phoneme Sequence Recognition using Convolutional Neural NetworksDec 07 2013Most phoneme recognition state-of-the-art systems rely on a classical neural network classifiers, fed with highly tuned features, such as MFCC or PLP features. Recent advances in ``deep learning'' approaches questioned such systems, but while some attempts ... More
Particular object retrieval with integral max-pooling of CNN activationsNov 18 2015Feb 24 2016Recently, image representation built upon Convolutional Neural Network (CNN) has been shown to provide effective descriptors for image search, outperforming pre-CNN features as short-vector representations. Yet such models are not compatible with geometry-aware ... More
Scaling of Navier-Stokes trefoil reconnectionOct 03 2016The reconnection of a trefoil vortex knot is examined numerically to determine how its helicity and two of its vorticity norms behave. During an initial phase, the helicity is remarkably preserved, as reported in recent experiments (Scheeler et al. 2014a). ... More
Bounds on a singular attractor in Euler using vorticity momentsDec 05 2012A new rescaling of the vorticity moments and their growth terms is used to characterise the evolution of anti-parallel vortices governed by the 3D Euler equations. To suppress unphysical instabilities, the initial condition uses a balanced profile for ... More
Scaling of Navier-Stokes trefoil reconnectionOct 03 2016May 26 2017Perturbed, helical trefoil vortex knots and a set of anti-parallel vortices are examined numerically to identify the scaling of their helicity and vorticity norms during reconnection. For the volume-integrated enstrophy $Z=\int\omega^2 dV$, a new scaling ... More
Orbit equivalence and sofic approximationFeb 13 2011Dec 20 2011Given an ergodic probability measure preserving dynamical system $\G\acts (X,\mu)$, where $\G$ is a finitely generated countable group, we show that the asymptotic growth of the number of finite models for the dynamics, in the sense of sofic approximations, ... More
Turbulence, representations, and trace-preserving actionsAug 13 2008We establish criteria for turbulence in certain spaces of C*-algebra representations and apply this to the problem of nonclassifiability by countable structures for group actions on a standard atomless probability space (X,\mu) and on the hyperfinite ... More
Trefoil knot structure during reconnectionMar 05 2017May 26 2017Three-dimensional images of evolving numerical trefoil vortex knots are used to study the growth and decay of the enstrophy and helicity. Negative helicity density ($h<0$) plays several roles. First, sheets of oppositely-signed helicity dissipation of ... More
Incompressible hydrodynamic turbulence from a chain reaction of vortex reconnection eventsDec 16 2012Jan 18 2013From a new anti-parallel initial condition using long vortices, three-dimensional turbulence forms after two reconnection steps and the formation of at least one vortex ring. The long domain is needed in order to accommodate the multiple reconnections, ... More
The least primitive root modulo $p^{2}$Aug 30 2019We provide an explicit estimate on the least primitive root mod $p^{2}$. We show, in particular, that every prime $p$ has a primitive root mod $p^{2}$ that is less than $p^{0.99}$.
Sofic dimension for discrete measured groupoidsNov 11 2011Nov 11 2012For discrete measured groupoids preserving a probability measure we introduce a notion of sofic dimension that measures the asymptotic growth of the number of sofic approximations on larger and larger finite sets. In the case of groups we give a formula ... More
Computational Euler HistoryJul 16 2006Jul 19 2006A new pseudospectral calculation of collapsing Euler vortices \cite{HouLi06} has called into question the long-term conclusions of singular behavior described earlier in \cite{Kerr93,Kerr05}. This review is designed to: improve the discussion of the detailed ... More
The energy budget in Rayleigh-Benard convectionDec 28 2000May 18 2001It is shown using three series of Rayleigh number simulations of varying aspect ratio AR and Prandtl number Pr that the normalized dissipation at the wall, while significantly greater than 1, approaches a constant dependent upon AR and Pr. It is also ... More
New examples of non-symmetric Einstein solvmanifolds of negative Ricci curvatureJun 21 2013Dec 31 2013We obtain new examples of non-symmetric Einstein solvmanifolds by combining two techniques. In \cite{T2}, H. Tamaru constructs new {\em attached} solvmanifolds, which are submanifolds of the solvmanifolds corresponding to noncompact symmetric spaces, ... More
Numerical generation of a vortex ring cascade in quantum turbulenceJun 20 2010Sep 21 2010A symmetric anti-parallel quantum pair of vortices is simulated using the three-dimensional Gross-Pitaevski equations. The initial development before cores interact directly demonstrates the traditional vortex dynamics of stretching, curvature and torsion ... More
Simulated Navier-Stokes trefoil reconnectionSep 10 2015The evolution and self-reconnection of a perturbed trefoil vortex knot is simulated, then compared to recent experimental measurements (Scheeler et al. 2014a). Qualitative comparisons using three-dimensional vorticity isosurfaces and lines, then quantitative ... More
Faint repetitions from a bright Fast Radio Burst sourceAug 27 2019We report the detection of repeat bursts from FRB 171019, one of the brightest fast radio bursts (FRBs) detected in the Australian Square Kilometre Array Pathfinder (ASKAP) fly's eye survey. Two bursts from the source were detected with the Green Bank ... More
wav2vec: Unsupervised Pre-training for Speech RecognitionApr 11 2019Sep 11 2019We explore unsupervised pre-training for speech recognition by learning representations of raw audio. wav2vec is trained on large amounts of unlabeled audio data and the resulting representations are then used to improve acoustic model training. We pre-train ... More
Evidence for a singularity in ideal magnetohydrodynamics: implications for fast reconnectionDec 10 1998Apr 20 1999Numerical evidence for a finite-time singularity in ideal 3D magnetohydrodynamics (MHD) is presented. The simulations start from two interlocking magnetic flux rings with no initial velocity. The magnetic curvature force causes the flux rings to shrink ... More
Nonnegatively curved homogeneous metrics obtained by scaling fibers of submersionsMar 11 2012Oct 30 2012We consider invariant Riemannian metrics on compact homogeneous spaces G/H where an intermediate subgroup K between G and H exists, so that the homogeneous space G/H is the total space of a Riemannian submersion. We study the question as to whether enlarging ... More
Arithmetic of degenerating principal variations of Hodge structure: examples arising from mirror symmetry and middle convolutionJul 15 2014Feb 08 2015We collect evidence in support of a conjecture of Griffiths, Green and Kerr on the arithmetic of extension classes of limiting mixed Hodge structures arising from semistable degenerations over a number field. After briefly summarizing how a result of ... More
Nonnegatively curved homogeneous metrics in low dimensionsJan 23 2012Oct 16 2012We consider invariant Riemannian metrics on compact homogeneous spaces $G/H$ where an intermediate subgroup $K$ between $G$ and $H$ exists. In this case, the homogeneous space $G/H$ is the total space of a Riemannian submersion. The metrics constructed ... More
New tests for a singularity of ideal MHDJan 07 2000Analysis using new calculations with 3 times the resolution of the earlier linked magnetic flux tubes confirms the transition from singular to saturated growth rate reported by Grauer and Marliani \cite{GrauerMar99} for the incompressible cases is confirmed. ... More
A note on quasi-positive curvature conditionsNov 16 2012We classify the triples $H \subset K \subset G$ of nested compact Lie groups which satisfy the "positive triple" condition that was shown by the second author to ensure that $G/H$ admits a metric with quasi-positive curvature. A few new examples of spaces ... More
Gamma-ray Activity in the Crab Nebula: The Exceptional Flare of April 2011Dec 08 2011Feb 06 2012The Large Area Telescope on board the Fermi satellite observed a gamma-ray flare in the Crab nebula lasting for approximately nine days in April of 2011. The source, which at optical wavelengths has a size of ~11 ly across, doubled its gamma-ray flux ... More
Helicity in Hydro and MHD ReconnectionDec 10 2000Helicity, a measure of the linkage of flux lines, has subtle and largely unknown effects upon dynamics. Both magnetic and hydrodynamic helicity are conserved for ideal systems and could suppress nonlinear dynamics. What actually happens is not clear because ... More
Periodic modulation in pulse arrival times from young pulsars: a renewed case for neutron star precessionOct 20 2015In a search for periodic variation in the arrival times of pulses from 151 young, energetic pulsars, we have identified seven cases of modulation consistent with one or two harmonics of a single fundamental with time-scale 0.5-1.5 yr. We use simulations ... More
Large Instrument Development for Radio AstronomyAug 26 2009This white paper offers cautionary observations about the planning and development of new, large radio astronomy instruments. Complexity is a strong cost driver so every effort should be made to assign differing science requirements to different instruments ... More
Identification of conserved moieties in metabolic networks by graph theoretical analysis of atom transition networksMay 17 2016Conserved moieties are groups of atoms that remain intact in all reactions of a metabolic network. Identification of conserved moieties gives insight into the structure and function of metabolic networks and facilitates metabolic modelling. All moiety ... More
Mass conserved elementary kinetics is sufficient for the existence of a non-equilibrium steady state concentrationSep 21 2011Feb 18 2012Living systems are forced away from thermodynamic equilibrium by exchange of mass and energy with their environment. In order to model a biochemical reaction network in a non-equilibrium state one requires a mathematical formulation to mimic this forcing. ... More
Measurement of the Fermi-LAT Localization PerformanceDec 19 2009We present results of a study of the localization capability of Fermi-LAT, using a large set of blazars with precise radio locations. Since the width of the PSF decreases with energy, the performance is typically dominated by a few high energy photons, ... More
Einstein@Home discovers a radio-quiet gamma-ray millisecond pulsarMar 19 2018Millisecond pulsars (MSPs) are old neutron stars that spin hundreds of times per second and appear to pulsate as their emission beams cross our line of sight. To date, radio pulsations have been detected from all rotation-powered MSPs. In an attempt to ... More
3D Euler about a 2D Symmetry PlaneFeb 22 2008Initial results from new calculations of interacting anti-parallel Euler vortices are presented with the objective of understanding the origins of singular scaling presented by Kerr (1993) and the lack thereof by Hou and Li (2006). Core profiles designed ... More
Transient vortex events in the initial value problem for turbulenceOct 19 2001Jan 27 2002A vorticity surge event that could be a paradigm for a wide class of bursting events in turbulence is studied to examine how the energy cascade is established and how this event could serve as a new test of LES turbulence models. This vorticity surge ... More
An inertial range length scale in structure functionsMay 03 2000It is shown using experimental and numerical data that within the traditional inertial subrange defined by where the third order structure function is linear that the higher order structure function scaling exponents for longitudinal and transverse structure ... More
New homogeneous Einstein metrics of negative Ricci curvatureAug 17 1999We construct new homogeneous Einstein spaces with negative Ricci curvature in two ways: First, we give a method for classifying and constructing a class of rank one Einstein solvmanifolds whose derived algebras are two-step nilpotent. As an application, ... More
Quasi-stationary simulations of the contact process on quenched networksJul 01 2011Nov 17 2011We present high-accuracy quasi-stationary (QS) simulations of the contact process in quenched networks, built using the configuration model with both structural and natural cutoffs. The critical behavior is analyzed in the framework of the anomalous finite ... More
Theoretically motivated search and detection of non-thermal pulsations from PSRs J1747-2958, J2021+3651, and J1826-1256Nov 20 2018Based on a theoretical selection of pulsars as candidates for detection at X-ray energies, we present an analysis of archival X-ray observations done with Chandra and XMM-Newton of PSR J1747-2958 (the pulsar in the "Mouse" nebula), PSR J2021+3651 (the ... More
Gravitational-wave cosmology across 29 decades in frequencyNov 18 2015Feb 28 2016Quantum fluctuations of the gravitational field in the early Universe, amplified by inflation, produce a primordial gravitational-wave background across a broad frequency band. We derive constraints on the spectrum of this gravitational radiation, and ... More
DistributedFBA.jl: High-level, high-performance flux balance analysis in JuliaNov 15 2016Motivation: Flux balance analysis, and its variants, are widely used methods for predicting steady-state reaction rates in biochemical reaction networks. The exploration of high dimensional networks with such methods is currently hampered by software ... More
First tests of a Micromegas TPC in a magnetic fieldDec 10 2004Since the summer of 2003, a large Micromegas TPC prototype (1000 channels, 50 cm drift, 50 cm diameter) has been operated in a 2T superconducting magnet at Saclay. A description of this apparatus and first results from cosmic ray tests are presented. ... More
On Estimating Maximum Sum Rate of MIMO Systems with Successive Zero-Forcing Dirty Paper Coding and Per-antenna Power ConstraintMay 14 2019In this paper, we study the sum rate maximization for successive zero-forcing dirty-paper coding (SZFDPC) with per-antenna power constraint (PAPC). Although SZFDPC is a low-complexity alternative to the optimal dirty paper coding (DPC), efficient algorithms ... More
Finding Zeros of Hölder Metrically Subregular Mappings via Globally Convergent Levenberg-Marquardt MethodsNov 30 2018Dec 05 2018We present two globally convergent Levenberg-Marquardt methods for finding zeros of H\"{o}lder metrically subregular mappings that may have non-isolated zeros. The first method unifies the Levenberg- Marquardt direction and an Armijo-type line search, ... More
Certifying cost annotations in compilersOct 08 2010We discuss the problem of building a compiler which can lift in a provably correct way pieces of information on the execution cost of the object code to cost annotations on the source code. To this end, we need a clear and flexible picture of: (i) the ... More
MetaboTools: A comprehensive toolbox for analysis of genome-scale metabolic modelsJun 09 2016Metabolomic data sets provide a direct read-out of cellular phenotypes and are increasingly generated to study biological questions. Our previous work revealed the potential of analyzing extracellular metabolomic data in the context of the metabolic model ... More
Low-complexity Approaches for MIMO Capacity with Per-antenna Power ConstraintApr 05 2017May 17 2017This paper proposes two low-complexity iterative algorithms to compute the capacity of a single-user multiple-input multiple-output channel with per-antenna power constraint. The first method results from manipulating the optimality conditions of the ... More
Alternating Optimization for Capacity Region of Gaussian MIMO Broadcast Channels with Per-antenna Power ConstraintApr 05 2017May 17 2017This paper characterizes the capacity region of Gaussian MIMO broadcast channels (BCs) with per-antenna power constraint (PAPC). While the capacity region of MIMO BCs with a sum power constraint (SPC) was extensively studied, that under PAPC has received ... More
A High-Resolution Study of Near-Infrared Diffuse Interstellar BandsSep 25 2014We present high-resolution echelle spectroscopic observations of the two near- infrared (NIR) Diffuse Interstellar Bands (DIBs) at 13175 A and 11797.5 A. The DIBs have been observed in a number of diffuse interstellar medium sightlines that exhibit a ... More
Limits on Planet Formation Around Young Pulsars and Implications for Supernova Fallback DisksJul 23 2015We have searched a sample of 151 young, energetic pulsars for periodic variation in pulse time-of-arrival arising from the influence of planetary companions. We are sensitive to objects with masses two orders of magnitude lower than those detectable with ... More
Room Temperature, Quantum-Limited THz Heterodyne Detection? Not YetJul 30 2019In their article, Wang et al. [1] report a new scheme for THz heterodyne detection using a laser-driven LTG-GaAs photomixer [2, 3] and make the impressive claim of achieving near quantum-limited sensitivity at room temperature. Unfortunately, their experimental ... More
Invariant Hilbert schemes and desingularizations of quotients by classical groupsJan 17 2013Jan 20 2014Let $W$ be a finite-dimensional representation of a reductive algebraic group $G$. The invariant Hilbert scheme $\mathcal{H}$ is a moduli space that classifies the $G$-stable closed subschemes $Z$ of $W$ such that the affine algebra $k[Z]$ is the direct ... More
Symmetric Powers of Hyperbolic Forms and of Trace Forms on Symbol AlgebrasJul 30 2013Let $K$ be a field with characteristic different from 2 and let $S$ be a symbol algebra over $K$. We compute the symmetric powers of hyperbolic quadratic forms over $K$. Also, we compute the symmetric powers of the quadratic trace form of $S$. In both ... More
Di-photon and Photon+b/c Production Cross Sections at Ecm=2TeVJun 24 2004The inclusive di-photon cross-section is measured in the central region and found to be in good agreement with NLO QCD predictions. Cross-sections are presented for events containing an energetic photon in addition to a heavy flavour jet. The ratio of ... More
Invariant Hilbert schemes and desingularizations of symplectic reductions for classical groupsMar 12 2013Dec 21 2013Let $G \subset GL(V)$ be a reductive algebraic subgroup acting on the symplectic vector space $W=(V \oplus V^*)^{\oplus m}$, and let $\mu:\ W \rightarrow Lie(G)^*$ be the corresponding moment map. In this article, we use the theory of invariant Hilbert ... More
Mathematical modelling of the vitamin C clock reactionAug 17 2018Chemical clock reactions are characterised by a relatively long induction period followed by a rapid `switchover' during which the concentration of a clock chemical rises rapidly. In addition to their interest in chemistry education, these reactions are ... More
Schémas de Hilbert invariants et théorie classique des invariantsNov 07 2012Let W be an affine variety equipped with an action of a reductive group G. The invariant Hilbert scheme is a moduli space which classifies the G-stable closed subschemes of W such that the affine algebra is the direct sum of simple G-modules with previously ... More
Mathematical modelling of the vitamin C clock reactionAug 17 2018Mar 24 2019Chemical clock reactions are characterised by a relatively long induction period followed by a rapid `switchover' during which the concentration of a \emph{clock chemical} rises rapidly. In addition to their interest in chemistry education, these reactions ... More
Approach and separation of quantum vortices with balanced coresOct 06 2014Feb 17 2016Using two innovations, smooth, but distinctly different, scaling laws for the numerical reconnection of pairs of initially orthogonal and anti-parallel quantum vortices are obtained using the three-dimensional Gross-Pitaevskii equations, the simplest ... More
Trace Forms of Symbol AlgebrasNov 27 2008Let S be a symbol algebra. The trace form of S is computed and it is shown how this form can be used to determine whether S is a division algebra or not. In addition, the exterior powers of the trace form of S are computed.
Sofic measure entropy via finite partitionsNov 05 2011We give a generator-free formulation of sofic measure entropy using finite partitions and establish a Kolmogorov-Sinai theorem. We also show how to compute the values for general Bernoulli actions in a concise way using the arguments of Bowen in the finite ... More
Improving Sensitivity to Weak Pulsations with Photon Probability WeightingMar 10 2011Sep 05 2011All gamma-ray telescopes suffer from source confusion due to their inability to focus incident high-energy radiation, and the resulting background contamination can obscure the periodic emission from faint pulsars. In the context of the Fermi Large Area ... More
Gauge theory of gravity and matterAug 08 2014It is shown how to write the first order action for gravity in a gauge theoretic formalism where the spin connection and frame field degrees of freedom are assimilated together into a gauge connection. It is then shown how to couple the theory to spin-0, ... More
On a bound of Heath-Brown for Dirichlet $L$-functions on the critical lineSep 25 2013Let $\chi$ a primitive character$\pmod q$ and consider the Dirichlet $L$-function $$L(s,\chi)=\sum_{n=1}^{\infty}\frac{\chi(n)}{n^s}.$$ We give a new proof of an upper bound of Heath-Brown for $|L(s,\chi)|$ on the critical line $s=1/2+it$
Entropy and induced dynamics on state spacesFeb 11 2003Jan 15 2004We consider the topological entropy of state space and quasi-state space homeomorphisms induced from C*-algebra automorphisms. Our main result asserts that, for automorphisms of separable exact C*-algebras, zero Voiculescu-Brown entropy implies zero topological ... More
Matricial quantum Gromov-Hausdorff distanceJul 30 2002We develop a matricial version of Rieffel's Gromov-Hausdorff distance for compact quantum metric spaces within the setting of operator systems and unital C*-algebras. Our approach yields a metric space of ``isometric'' unital complete order isomorphism ... More
Incomplete exponential sums over exponential functionsFeb 18 2013We extend some methods of bounding exponential sums of the type $\displaystyle\sum_{n\le N}e^{2\pi iag^n/p}$ to deal with the case when $g$ is not necessarily a primitive root. We also show some recent results of Shkredov concerning additive properties ... More
Some multiplicative equations in finite fieldsMar 21 2019In this paper we consider estimating the number of solutions to multiplicative equations in finite fields when the variables run through certain sets with high additive structure. In particular, we consider estimating the multiplicative energy of generalized ... More
Dissecting a Small InfiniBand Application Using the Verbs APIMay 10 2011May 24 2011InfiniBand is a switched fabric interconnect. The InfiniBand specification does not define an API. However the OFED package, libibverbs, has become the default API on Linux and Solaris systems. Sparse documentation exists for the verbs API. The simplest ... More
Observing and modeling the gamma-ray emission from pulsar/pulsar wind nebula complex PSR J0205+6449/3C 58Mar 28 2018We present the results of the analysis of 8 years of Fermi-LAT data of the pulsar/pulsar wind nebula complex PSR J0205+6449/3C 58. Using a contemporaneous ephemeris, we carried out a detailed analysis of PSR J0205+6449 both during its off-peak and on-peak ... More
A variational principle for computing nonequilibrium fluxes and potentials in genome-scale biochemical networksMay 08 2011Sep 19 2011We derive a convex optimization problem on a steady-state nonequilibrium network of biochemical reactions, with the property that energy conservation and the second law of thermodynamics both hold at the problem solution. This suggests a new variational ... More
Dimension and dynamical entropy for metrized C*-algebrasNov 04 2002We introduce notions of dimension and dynamical entropy for unital C*-algebras ``metrized'' by means of c-Lip-norms, which are complex-scalar versions of the Lip-norms constitutive of Rieffel's compact quantum metric spaces. Our examples involve UHF algebras ... More
Hamiltonian analysis of self-dual gauge gravityApr 15 2015The Hamiltonian analysis of the self-dual gauge gravity theory is carried out. The resulting canonical structure is equivalent to that of self-dual gravity.
On the constant in the Polya-Vinogradov inequalityJul 25 2018In this paper we obtain a new constant in the P\'{o}lya-Vinogradov inequality. Our argument follows previously established techniques which use the Fourier expansion of an interval to reduce to Gauss sums. Our improvement comes from approximating an interval ... More
Incomplete Gauss sums modulo primesJun 18 2017We obtain a new bound for incomplete Gauss sums modulo primes. Our argument falls under the framework of Vinogradov's method which we use to reduce the problem under consideration to bounding the number of solutions to two distinct systems of congruences. ... More
Some mixed character sumsOct 14 2014In this paper we consider a variety of mixed character sums. In particular we extend a bound of Heath-Brown and Pierce to the case of squarefree modulus, improve on a result of Chang for mixed sums in finite fields, we show in certain circumstances we ... More
Solutions to polynomial congruences in well shaped setsOct 05 2012Feb 26 2013We use a generalization of Vinogradov's mean value theorem of S. Parsell, S. Prendiville and T. Wooley and ideas of W. Schmidt to give nontrivial bounds for the number of solutions to polynomial congruences, for arbitrary polynomials, when the solutions ... More
Character sums over shifted primesAug 07 2013Sep 24 2013For integer $q$, let $\chi$ be a primitive multiplicative character$\pmod q.$ For integer $a$ coprime to $q$, we obtain a new bound for the sums $$\sum_{n\le N}\Lambda(n)\chi(n+a),$$ where $\Lambda(n)$ is the von Mangoldt function. This bound improves ... More
Products of Toeplitz Operators on a Vector Valued Bergman SpaceApr 26 2008We give a necessary and a sufficient condition for the boundedness of the Toeplitz product $T_FT_{G^*}$ on the vector valued Bergman space $L_a^2(\mathbb{C}^n)$, where $F$ and $G$ are matrix symbols with scalar valued Bergman space entries. The results ... More
Motivic irrationality proofsAug 13 2017We exhibit geometric conditions on a family of toric hypersurfaces under which the value of a canonical normal function at a point of maximal unipotent monodromy is irrational.
Higher Abel-Jacobi maps for 0-cyclesApr 05 2005Mar 13 2006Starting from the candidate Bloch-Beilinson filtration on Chow groups of 0-cycles constructed by J. Lewis, we develop and describe geometrically a series of Hodge-theoretic invariants defined on the graded pieces. Explicit formulas (in terms of currents ... More
Existence of Positive Steady States for Mass Conserving and Mass-Action Chemical Reaction Networks with a Single Terminal-Linkage ClassMay 12 2011Oct 20 2011We establish that mass conserving single terminal-linkage networks of chemical reactions admit positive steady states regardless of network deficiency and the choice of reaction rate constants. This result holds for closed systems without material exchange ... More
A geometric approach to Voiculescu-Brown entropyApr 29 2003A basic problem in dynamics is to identify systems with positive entropy, i.e., systems which are "chaotic." While there is a vast collection of results addressing this issue in topological dynamics, the phenomenon of positive entropy remains by and large ... More
Likelihood Methods for the Detection and Characterization of Gamma-ray Pulsars with the Fermi Large Area TelescopeJan 31 2011The sensitivity of the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope allows detection of thousands of new gamma-ray sources and detailed characterization of the spectra and variability of bright sources. Unsurprisingly, this increased ... More
Topological quantum field theory and quantum gravityAug 07 2014This thesis is broadly split into two parts. In the first part, simple state sum models for minimally coupled fermion and scalar fields are constructed on a $1$-manifold. The models are independent of the triangulation and give the same result as the ... More