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Results for "Ronan M. Kerr"

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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
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
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
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
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
Reliable and efficient solution of genome-scale models of Metabolism and macromolecular ExpressionMay 31 2016Sep 26 2016Constraint-Based Reconstruction and Analysis (COBRA) is currently the only methodology that permits integrated modeling of Metabolism and macromolecular Expression (ME) at genome-scale. Linear optimization computes steady-state flux solutions to ME models, ... 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
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
New examples of complete Calabi-Yau metrics on $\mathbb{C}^n$ for $n\ge 3$May 24 2017Jun 16 2017For each $n\ge 3$, we construct on $\mathbb{C}^n$ examples of complete Calabi-Yau metrics of Euclidean volume growth having a tangent cone at infinity with singular cross-section.
Automated Phase Mapping with AgileFD and its Application to Light Absorber Discovery in the V-Mn-Nb Oxide SystemOct 06 2016Rapid construction of phase diagrams is a central tenet of combinatorial materials science with accelerated materials discovery efforts often hampered by challenges in interpreting combinatorial x-ray diffraction datasets, which we address by developing ... More
Automorphisms of $\mathbb{P}^1$-bundles over rational surfacesJul 05 2017Sep 19 2017In this paper we provide the complete classification of $\mathbb{P}^1$-bundles over smooth projective rational surfaces whose neutral component of the automorphism group is maximal. Our results hold over any algebraically closed field of characteristic ... More
Real structures on horospherical varietiesAug 31 2018We study the equivariant real structures on complex horospherical varieties, generalizing classical results known for toric varieties and flag varieties. In particular, we obtain a necessary and sufficient condition for the existence of such real structures ... More
Limit theorems for Markov walks conditioned to stay positive under a spectral gap assumptionJul 26 2016Jul 27 2016Consider a Markov chain $(X_n)_{n\geqslant 0}$ with values in the state space $\mathbb X$. Let $f$ be a real function on $\mathbb X$ and set $S_0=0,$ $S_n = f(X_1)+\cdots + f(X_n),$ $n\geqslant 1$. Let $\mathbb P_x$ be the probability measure generated ... More
Generalized Hadamard full propelinear codesJun 14 2019Codes from generalized Hadamard matrices have already been introduced. Here we deal with these codes when the generalized Hadamard matrices are cocyclic. As a consequence, a new class of codes that we call generalized Hadamard full propelinear codes turns ... 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
Near Optimal Exploration-Exploitation in Non-Communicating Markov Decision ProcessesJul 06 2018Mar 20 2019While designing the state space of an MDP, it is common to include states that are transient or not reachable by any policy (e.g., in mountain car, the product space of speed and position contains configurations that are not physically reachable). This ... More
Quasi-asymptotically conical Calabi-Yau manifoldsNov 14 2016Mar 15 2019We construct new examples of quasi-asymptotically conical (QAC) Calabi-Yau manifolds that are not quasi-asymptotically locally Euclidean (QALE). We do so by first providing a natural compactification of QAC-spaces by manifolds with fibred corners and ... 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
Borel complexity and automorphisms of C*-algebrasApr 14 2014We show that if $A$ is $\mathcal{Z}$, $\mathcal{O}_2$, $\mathcal{O}_{\infty}$, a UHF algebra of infinite type, or the tensor product of a UHF algebra of infinite type and $\mathcal{O}_{\infty}$, then the conjugation action $\mathrm{Aut}(A) \curvearrowright ... More
Hard X-ray and UV Observations of the 2005 January 15 Two-ribbon FlareOct 20 2011In this paper, we present comprehensive analysis of a two-ribbon flare observed in UV 1600{\AA} by Transition Region and Coronal Explorer and in HXRs by Reuven Ramaty High Energy Solar Spectroscopic Imager. HXR (25-100 keV) imaging observations show two ... More
Smoothing of rational singularities and Hodge structureJun 10 2019We show that the frontier Hodge numbers $h^{p,q}$ (that is, for $pq(n-p)(n-q)=0$) do not change by passing to a desingularization of the singular fiber of a one-parameter degeneration of smooth projective varieties of dimension $n$ if the singular fiber ... 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
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
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
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
Discovery of Soft X-ray Pulsations from PSR J1231-1411 using NICERMay 28 2019We report the discovery of soft X-ray pulsations from the nearby millisecond pulsar PSR J1231$-$1411 using NICER. The pulsed emission is characterized by a broad and asymmetric main pulse and a much fainter secondary interpulse, with a total pulsed count ... More
Exploration Bonus for Regret Minimization in Undiscounted Discrete and Continuous Markov Decision ProcessesDec 11 2018We introduce and analyse two algorithms for exploration-exploitation in discrete and continuous Markov Decision Processes (MDPs) based on exploration bonuses. SCAL$^+$ is a variant of SCAL (Fruit et al., 2018) that performs efficient exploration-exploitation ... More
Efficient Bias-Span-Constrained Exploration-Exploitation in Reinforcement LearningFeb 12 2018Jul 06 2018We introduce SCAL, an algorithm designed to perform efficient exploration-exploitation in any unknown weakly-communicating Markov decision process (MDP) for which an upper bound $c$ on the span of the optimal bias function is known. For an MDP with $S$ ... 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
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
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
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
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
Fourier-Correlation ImagingMay 10 2017We investigate to what extent correlating the Fourier components at slightly shifted frequencies of the fluctuations of the electric field measured with a one-dimensional antenna array on board of a satellite flying over a plane, allows one to measure ... More
Generalization of the Van Cittert--Zernike theorem: observers moving with respect to sourcesJun 15 2015The use of the Van Cittert--Zernike theorem for the formulation of the visibility function in satellite-based Earth observation with passive radiometers does not take into account the relative motion of the observer (the satellite antenna) with respect ... 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
Fully Convolutional Speech RecognitionDec 17 2018Apr 09 2019Current state-of-the-art speech recognition systems build on recurrent neural networks for acoustic and/or language modeling, and rely on feature extraction pipelines to extract mel-filterbanks or cepstral coefficients. In this paper we present an alternative ... 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
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
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
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
An Efficient Precoder Design for Multiuser MIMO Cognitive Radio Networks with Interference ConstraintsAug 15 2016We consider a linear precoder design for an underlay cognitive radio multiple-input multiple-output broadcast channel, where the secondary system consisting of a secondary base-station (BS) and a group of secondary users (SUs) is allowed to share the ... More
Diamonds and PAHs in the Circumstellar Environment of the Herbig Ae/Be Star Elias 1Aug 16 2006We report long-slit spectroscopic observations of the Herbig Ae/Be star Elias 1 in the 3.2-3.6 mum region covering the C-H stretch emission features of hydrogen-terminated diamonds and PAHs. The data were recorded at UKIRT using UIST and yield information ... 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
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
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
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
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
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
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
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
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
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
Ceramics Fragments Digitization by Photogrammetry, Reconstructions and ApplicationsDec 03 2014This paper presents an application of photogrammetry on ceramic fragments from two excavation sites located north-west of France. The restitution by photogrammetry of these different fragments allowed reconstructions of the potteries in their original ... 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
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
The UKIRT Infrared Deep Sky Survey Second Data ReleaseMar 02 2007Jul 26 2007The UKIRT Infrared Deep Sky Survey (UKIDSS) is a set of five large near-infrared surveys, covering a complementary range of areas, depths, and Galactic latitudes. The UKIDSS Second Data Release (DR2) includes the First Data Release (DR1), with minor improvements, ... 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
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
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
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
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.
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
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
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
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
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
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
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
Martingale transforms, the dyadic shift and the Hilbert transform: a sufficient condition for boundedness between matrix weighted spacesJun 22 2009Jun 23 2010We show sufficient conditions on matrix weights $U$ and $V$ for the martingale transforms to be uniformly bounded from $L^2(V)$ to $L^2(U)$. We also show that these conditions imply the uniform boundedness of the dyadic shifts as well as the boundedness ... More
Rational exponential sums over the divisor functionSep 24 2013We consider a problem posed by Shparlinski, of giving nontrivial bounds for rational exponential sums over the arithmetic function $\tau(n)$, counting the number of divisors of $n$. This is done using some ideas of Sathe concerning the distribution in ... More
Temporal Variability of Waves at the Proton Cyclotron Frequency Upstream from Mars: Implications for Mars Distant Hydrogen ExosphereApr 26 2013We report on the temporal variability of the occurrence of waves at the local proton cyclotron frequency upstream from the Martian bow shock from Mars Global Surveyor observations during the first aerobraking and science phasing orbit periods. Observations ... 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
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
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.
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