Results for "A. Ramachandran"

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Local Pulsars; A note on the Birth-Velocity DistributionJun 22 1998We explore a simple model for the representation of the observed distributions of the motions, and the characteristic ages of the local population of pulsars. The principal difference from earlier models is the introduction of a unique value, S, for the ... More
The study of threshold behaviour of effective potential for $^{6}$Li+$^{58,64}$Ni systemsJan 30 2008The elastic scattering for $^6$Li+$^{64}$Ni system was measured in the bombarding energy range of 13 MeV $\leq$ $E_{lab}$ $\leq$ 26 MeV. A phenomenological optical model analysis was performed and the behaviour of the surface strengths of the potential ... More
Improving Pulsar Distances by Modelling Interstellar ScatteringJun 22 1998We present here a method to study the distribution of electron density fluctuations in pulsar directions as well as to estimate pulsar distances. The method, based on a simple two-component model of the scattering medium discussed by Gwinn et al. (1993), ... More
The arc length of a random lemniscateOct 31 2016Feb 01 2017A polynomial lemniscate is a curve in the complex plane defined by $\{z \in \mathbb{C}:|p(z)|=t\}$. Erd\"os, Herzog, and Piranian posed the extremal problem of determining the maximum length of a lemniscate $\Lambda=\{ z \in \mathbb{C}:|p(z)|=1\}$ when ... More
Who Contributes to the Knowledge Sharing Economy?Aug 27 2015Information sharing dynamics of social networks rely on a small set of influencers to effectively reach a large audience. Our recent results and observations demonstrate that the shape and identity of this elite, especially those contributing \emph{original} ... More
The Galactic WC and WO stars: The impact of revised distances from Gaia DR2 and their role as massive black hole progenitorsJul 11 2018Jan 09 2019Wolf-Rayet stars of the carbon sequence (WC stars) are an important cornerstone in the late evolution of massive stars before their core collapse. As core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage ... More
A note on the critical points of the torsion functionJul 19 2019Let $\Omega\subset\mathbb{C}$ be a bounded domain. In this note, we use complex variable methods to study the number of critical points of the function $v=v_\Omega$ that solves the elliptic problem $\Delta v = -2$ in $\Omega,$ with boundary values $v=0$ ... More
Extensions of abelian varieties defined over a number fieldDec 03 2002Aug 26 2004We study the arithmetic aspects of the finite group of extensions of abelian varieties defined over a number field. In particular, we establish relations with special values of L-functions and congruences between modular forms.
MIMO-OTFS in High-Doppler Fading Channels: Signal Detection and Channel EstimationMay 06 2018Orthogonal time frequency space (OTFS) modulation is a recently introduced multiplexing technique designed in the 2-dimensional (2D) delay-Doppler domain suited for high-Doppler fading channels. OTFS converts a doubly-dispersive channel into an almost ... More
A Weil-Barsotti formula for Drinfeld modulesJul 20 2001Sep 07 2002We study the group of extensions in the category of Drinfeld modules and Anderson's t-modules, and we show in certain cases that this group can itself be given the structure of a t-module. Our main result is a Drinfeld module analogue of the Weil-Barsotti ... More
Higher-power harmonic maps and sectionsFeb 08 2019The variational theory of higher-power energy is developed for mappings between Riemannian manifolds, and more generally sections of submersions of Riemannian manifolds, and applied to sections of Riemannian vector bundles and their sphere subbundles. ... More
Higher-power harmonic maps and sectionsFeb 08 2019Mar 15 2019The variational theory of higher-power energy is developed for mappings between Riemannian manifolds, and more generally sections of submersions of Riemannian manifolds, and applied to sections of Riemannian vector bundles and their sphere subbundles. ... More
Upper Limits on the Pulsed Radio Emission from the Geminga Pulsar at 35 & 327 MHzAug 21 1998We report here our observations at 35 MHz and 327 MHz made in the direction of the Gamma Ray pulsar Geminga. Based on the observed absence of any significant pulsed emission from this source above our detection thresholds at the two frequencies, we obtain ... More
The observational evidence pertinent to possible kick mechanisms in neutron starsOct 06 1999We examine available observations on pulsars for evidence pertaining to mechanisms proposed to explain the origin of their velocities. We find that mechanisms predicting a correlation between the rotation axis and the pulsar velocity are ruled out. Also, ... More
Possible EIT-like effects in strong-field photodissociation of carbon disulphideFeb 26 2007CS$_2$ molecules are spatially aligned upon irradiation by intense (1-100 TW cm$^{-2}$), 35 ps pulses of 512 nm or 355 nm light. When both colours are simultaneously present, spatial alignment disappears. We draw analogy with weak-field illumination of ... More
The backscattering of polarised light from turbid media - An analysis of the azimuthal intensity variations and its implications for the position of the source of diffusing radiationJun 15 1999We study the azimuthal variation in the backscattered intensity that is seen when polarised light is scattered by a turbid medium. We present experimental observations of these intensity variations in colloidal suspensions over a wide range of optical ... More
Convexity of level lines of Martin functions and applicationsOct 01 2017Jan 21 2018Let $\Omega$ be an unbounded domain in $\mathbb{R}\times\mathbb{R}^{d}.$ A positive harmonic function $u$ on $\Omega$ that vanishes on the boundary of $\Omega$ is called a Martin function. In this note, we show that, when $\Omega$ is convex, the superlevel ... More
The closed range property for the $\overline{\partial}$-operator on planar domainsJan 14 2019Let $\Omega\subset\mathbb{C}$ be an open set. We show that $\overline{\partial}$ has closed range in $L^{2}(\Omega)$ if and only if the Poincar\'e-Dirichlet inequality holds. Moreover, we give necessary and sufficient potential-theoretic conditions for ... More
Collaboration of AI Agents via Cooperative Multi-Agent Deep Reinforcement LearningJun 30 2019There are many AI tasks involving multiple interacting agents where agents should learn to cooperate and collaborate to effectively perform the task. Here we develop and evaluate various multi-agent protocols to train agents to collaborate with teammates ... More
Simple Iterative Incompressible Smoothed Particle HydrodynamicsAug 06 2019In this paper a simple, robust, and general purpose approach to implement the Incompressible Smoothed Particle Hydrodynamics (ISPH) method is proposed. The new approach is well suited for implementation on CPUs and GPUs. The method is matrix-free and ... More
Intrinsic short time scale variability of W3(OH) maserAug 04 2006We have studied the OH masers in the star forming region, W3(OH), with data obtained from the Very Long Baseline Array (VLBA). The data provide an angular resolution of $\sim$5 mas, and a velocity resolution of 106 m s$^{-1}$. A novel analysis procedure ... More
Directed Non-Targeted Mass Spectrometry and Chemical Networking for Discovery of EicosanoidsJun 05 2018Eicosanoids and related species are critical, small bioactive mediators of human physiology and inflammation. While ~1100 distinct eicosanoids have been predicted to exist, to date, less than 150 of these molecules have been measured in humans, limiting ... More
Search for Discrete Refractive Scattering EventsNov 23 2000We have searched for discrete refractive scattering events (including effects due to possible non-multiple diffractive scattering) at meter wavelengths in the direction of two close by pulsars B0950+08 and B1929+10, where we looked for spectral signatures ... More
Imaging in turbid media using quasi-ballistic photonsJun 13 1999We study by means of experiments and Monte Carlo simulations, the scattering of light in random media, to determine the distance upto which photons travel along almost undeviated paths within a scattering medium, and are therefore capable of casting a ... More
PSR B0809+74: Understanding Its Perplexing Subpulse-separation (P2) VariationsJun 09 2004The longitude separation between adjacent drifting subpulses, $P_2$, is roughly constant for many pulsars. It was then perplexing when pulsar B0809+74 was found to exhibit substantial variations in this measure, both with wavelength and with longitude ... More
Frequency analysis and resonant operation for efficient capacitive deionizationJun 07 2018Capacitive deionization (CDI) performance metrics can vary widely with operating methods. We here develop a theory around and experimentally demonstrate a new operation for CDI that uses sinusoidal forcing voltage (or sinusoidal current). We use a dynamic ... More
Resonant Bend Loss in Leakage Channel FibersMay 24 2012Leakage channel fibers, designed to suppress higher-order modes, demonstrate resonant power loss at certain critical radii of curvature. Outside the resonance, the power recovers to the levels offset by the usual mechanism of bend-induced loss. Using ... More
Resilience by Reconfiguration: Exploiting Heterogeneity in Robot TeamsMar 12 2019May 15 2019We propose a method to maintain high resource in a networked heterogeneous multi-robot system to resource failures. In our model, resources such as and computation are available on robots. The robots engaged in a joint task using these pooled resources. ... More
Resilience by Reconfiguration: Exploiting Heterogeneity in Robot TeamsMar 12 2019We propose a method to maintain high resource in a networked heterogeneous multi-robot system to resource failures. In our model, resources such as and computation are available on robots. The robots engaged in a joint task using these pooled resources. ... More
Exploring Zeptosecond Quantum Equilibration Dynamics: From Deep-Inelastic to Fusion-Fission Outcomes in $^{58}$Ni+$^{60}$Ni ReactionsDec 26 2017Energy dissipative processes play a key role in how quantum many-body systems dynamically evolve towards equilibrium. In closed quantum systems, such processes are attributed to the transfer of energy from collective motion to single-particle degrees ... More
Higher Euler characteristicsSep 17 2015We provide a natural interpretation of the secondary Euler characteristic and introduce higher Euler characteristics. For a compact oriented manifold of odd dimension, the secondary Euler characteristic recovers the Kervaire semi-characteristic. We prove ... More
automan: a simple, Python-based, automation framework for numerical computingDec 11 2017Feb 04 2018We present an easy-to-use, Python-based framework that allows a researcher to automate their computational simulations. In particular the framework facilitates assembling several long-running computations and producing various plots from the data produced ... More
Spin Puzzle in NucleonFeb 06 1995Feb 07 1995The object of this brief review is to reconcile different points of view on how the spin of proton is made up from its constituents. On the basis of naive quark model with flavour symmetry such as isospin or SU(3) one finds a static description. On the ... More
Have We At Last Found The A-toms?Oct 28 1997It is argued that the three families of quarks and leptons are the building blocks of all matter and all forces (leaving out gravity) among them are mediated by photons ($\gamma$), the weak bosons ($W^\pm$ and $Z$) and the gluons.
Automated Improvement for Component ReuseMay 11 2005Jun 27 2012Software component reuse is the key to significant gains in productivity. However, the major problem is the lack of identifying and developing potentially reusable components. This paper concentrates on our approach to the development of reusable software ... More
Duality of Albanese and Picard 1-motivesApr 07 1998Jan 31 2001We define Albanese and Picard 1-motives of smooth (simplicial) schemes over a perfect field. For smooth proper schemes, these are the classical Albanese and Picard varieties. For a curve, these are t he homological 1-motive of Lichtenbaum and the motivic ... More
Asymptotic behavior of positive harmonic functions in certain unbounded domainsNov 09 2012Dec 11 2012We derive asymptotic estimates at infinity for positive harmonic functions in a large class of non-smooth unbounded domains. These include domains whose sections, after rescaling, resemble a Lipschitz cylinder or a Lipschitz cone, e.g., various paraboloids ... More
Quantum view of MassAug 29 2012Oct 07 2012The classical view of mass is that it quantifies the amount of substance and is a kinematical parameter. All matter has an attribute of mass and is a conserved quantity in any interaction. With the advent of special relativity, mass became no longer a ... More
Zeta functions, Grothendieck groups, and the Witt ringJul 07 2014Jul 10 2014We prove some results connecting the zeta functions of varieties over finite fields with the big Witt ring over $\mathbb Z$. We explore relations with motivic measures and a classical formula of Macdonald on invariants of symmetric products of a variety. ... More
Probing Gluon Helicity with Dijets from $\sqrt s$ = 510 GeV Polarized Proton Collisions at STARAug 03 2016The production of jets in polarized proton collisions at STAR is dominated by quark-gluon and gluon-gluon scattering processes. The dijet longitudinal double-spin asymmetry $(A_{LL})$ is sensitive to the helicity distributions and may be used to extract ... More
A Truth Serum for Large-Scale EvaluationsJul 25 2015Feb 16 2018A major challenge in obtaining large-scale evaluations, e.g., product or service reviews on online platforms, labeling images, grading in online courses, etc., is that of eliciting honest responses from agents in the absence of verifiability. We propose ... More
EmuFog: Extensible and Scalable Emulation of Large-Scale Fog Computing InfrastructuresSep 22 2017The diversity of Fog Computing deployment models and the lack of publicly available Fog infrastructure makes the design of an efficient application or resource management policy a challenging task. Such research often requires a test framework that facilitates ... More
Values of zeta functions at s=1/2Feb 24 2005Mar 14 2005We study the behaviour near s=1/2 of zeta functions of varieties over finite fields F_q with q a square. The main result is an Euler-characteristic formula for the square of the special value at s=1/2. The Euler-characteristic is constructed from the ... More
Chiral Soliton Model vs Pentaquark Structure for Θ(1540)Nov 08 2004May 24 2005The exotic baryon $\Theta^+$ (1540 MeV)$ is visualised as an expected (iso) rotational excitation in the Chiral Soliton Model. It is also argued as a Pentaquark baryon state in a constituent quark model with strong diquark correlations. I contrast the ... More
Kinematics of Radio PulsarsNov 05 1999Observations of proper motions and their statistical analyses show that the predominant number of pulsars have velocities of the order of 200-250 km/sec. The pulsar population exhibits "asymmetric drift" in the Galaxy. Though there are compelling evidences ... More
Intermodal group velocity engineering for broadband nonlinear opticsJun 07 2018Interest in the nonlinear properties of multi-mode optical waveguides has seen a recent resurgence on account of the large dimensionality afforded by the platform. However, a perceived fundamental limitation of intermodal parametric interactions - that ... More
Discovery of Soliton Self-Mode Conversion in Multimode Optical FibersMay 15 2018Nonlinear optical wave propagation manifests in a multitude of frequencies generated from quantum-noise, and selecting desired nonlinear products usually requires seeding the medium with extraneous waves, employing spatial or spectral filters, or operation ... More
Conclusive evidence of quasifission in heavy-ion induced reactions in neutron-deficient sub-lead nuclei exhibiting asymmetric fissionJul 15 2019Fission fragment mass distributions of 191Au, a nucleus in the newly identified island of mass asymmetric fission in the sub-lead region, have been measured down to excitation energy of ~ 20 MeV above the fission barrier via two different entrance channels, ... More
A note on the Bloch-Tamagawa space and Selmer groupsJan 04 2015For any abelian variety $A$ over a number field, we construct an extension of the Tate-Shafarevich group by the Bloch-Tamagawa space using the recent work of Lichtenbaum and Flach. This gives a new example of a Zagier sequence for the Selmer group of ... More
From Jacobians to one-motives: exposition of a conjecture of DeligneFeb 05 2001Deligne has conjectured that certain mixed Hodge theoretic invariants of complex algebraic invariants are motivic. This conjecture specializes to an algebraic construction of the Jacobian for smooth projective curves, which was done by A. Weil. The conjecture ... More
One-motives and a conjecture of DeligneJun 22 1998Feb 12 2003We introduce new motivic invariants of arbitrary varieties over a perfect field. These cohomological invariants take values in the category of one-motives (considered up to isogeny in positive characteristic). The algebraic definition of these invariants ... More
Stability and onset of two-dimensional viscous fingering in immiscible fluidsApr 09 2017Viscous flows in a quasi-two-dimensional Hele-Shaw geometry can lead to an interfacial instability when one fluid, of viscosity $\eta_{in}$ displaces another of higher viscosity, $\eta_{out}$. Recent studies have shown that there is a delay in the onset ... More
Squeezing of a coupled state of two spinorsApr 04 2002The notion of spin squeezing involves reduction in the uncertainty of a component of the spin vector below a certain limit. This aspect has been studied earlier for pure and mixed states of definite spin. In this paper, this study has been extended to ... More
Architectural Pattern of Health Care System Using GSM NetworksDec 09 2013Large-scale networked environments, such as the Internet, possess the characteristics of centralised data, centralised access and centralised control; this gives the user a powerful mechanism for building and integrating large repositories of centralised ... More
Study of transfer reaction channel in $^{12}$C + $^{27}$Al systemJul 28 2011The 1p transfer channel in the $^{27}$Al($^{12}$C, $^{11}$B)$^{28}$Si reaction has been studied at E$_{lab}$ = 73, 81 and 85 MeV. The finite range distorted wave Born approximation calculations have been performed using phenomenological optical model ... More
Spin squeezing of mixed systemsOct 26 2000The notion of spin squeezing has been discussed in this paper using the density matrix formalism. Extending the definition of squeezing for pure states given by Kitagawa and Ueda in an appropriate manner and employing the spherical tensor representation, ... More
Probing drifting and nulling mechanisms through their interaction in PSR B0809+74Aug 19 2002Nov 12 2002Both nulling and subpulse drifting are poorly understood phenomena. We probe their mechanisms by investigating how they interact in PSR B0809+74. We find that the subpulse drift is not aliased but directly reflects the actual motion of the subbeams. The ... More
Bandwidth-Efficient Synchronization for Fiber Optic Transmission: System Performance MeasurementsJan 05 2018In this article, we first provide a brief overview of optical transmission systems and some of their performance specifications. We then present a simple, robust, and bandwidth-efficient OFDM synchronization method, and carry out measurements to validate ... More
Orientations of Spin and Magnetic Dipole Axes of Pulsars in the J0737--3039 Binary Based on Polarimetry Observations at the Green Bank TelescopeFeb 02 2004We report here the first polarimetric measurements of the pulsars in the J0737-3039 binary neutron star system using the Green Bank Telescope. We conclude both that the primary star (A) has a wide hollow cone of emission, which is an expected characteristic ... More
A Machine Learning-Based Detection Technique for Optical Fiber Nonlinearity MitigationFeb 27 2019We investigate the performance of a machine learning classification technique, called the Parzen window, to mitigate the fiber nonlinearity in the context of dispersion managed and dispersion unmanaged systems. The technique is applied for detection at ... More
Simple sampling clock synchronisation scheme for reduced-guard-interval coherent optical OFDM systemsJan 05 2018A simple data-aided scheme for sampling clock synchronisation in reduced-guard-interval coherent optical orthogonal frequency division multiplexing (RGI-CO-OFDM) systems is proposed. In the proposed scheme, the sampling clock offset (SCO) is estimated ... More
Robust Faster-than-Nyquist PDM-mQAM Systems with Tomlinson-Harashima PrecodingJan 04 2018A training-based channel estimation algorithm is proposed for the faster-than-Nyquist PDM-mQAM (m = 4, 16, 64) systems with Tomlinson-Harashima precoding (THP). This is robust to the convergence failure phenomenon suffered by the existing algorithm, yet ... More
A Machine Learning-Based Detection Technique for Optical Fiber Nonlinearity MitigationFeb 27 2019Mar 06 2019We investigate the performance of a machine learning classification technique, called the Parzen window, to mitigate the fiber nonlinearity in the context of dispersion managed and dispersion unmanaged systems. The technique is applied for detection at ... More
Light scattering from a magnetically tunable dense random medium with weak dissipation : ferrofluidApr 21 2011We present a semi-phenomenological treatment of light transmission through and its reflection from a ferrofluid, which we regard as a magnetically tunable system of dense random dielectric scatterers with weak dissipation. Partial spatial ordering is ... More
Interpretation of coincidence data from strip detectors and extraction of absolute cross section using 3-body Monte Carlo simulation methodJan 09 2019Accurate knowledge of the response of the detection system is very crucial for unambiguous interpretation of the experimental data. A simulation code has been developed using the Monte Carlo technique involving 3-body kinematics for the analysis of data ... More
{Interstellar Plasma Weather Effects in Long-term Multi-frequency Timing of Pulsar B1937+21Jan 11 2006We report here on variable propagation effects in over twenty years of multi-frequency timing analysis of pulsar PSR B1937+21 that determine small-scale properties of the intervening plasma as it drifts through the sight line. The phase structure function ... More
Coastline Kriging: A Bayesian ApproachJul 06 2018Statistical interpolation of chemical concentrations at new locations is an important step in assessing a worker's exposure level. When measurements are available from coastlines, as is the case in coastal clean-up operations in oil spills, one may need ... More
A survey on fiber nonlinearity compensation for 400 Gbps and beyond optical communication systemsAug 21 2017Optical communication systems represent the backbone of modern communication networks. Since their deployment, different fiber technologies have been used to deal with optical fiber impairments such as dispersion-shifted fibers and dispersion-compensation ... More
Evidence for transfer followed by breakup in 7Li + 65CuDec 21 2005The observation of a large cross-section for the alpha + d channel compared to breakup into the alpha + t channel from an exclusive measurement for the 7Li+65Cu system at 25 MeV is presented. A detailed analysis of the angular distribution using coupled ... More
PoWR grids of non-LTE model atmospheres for OB-type stars of various metallicitiesNov 15 2018The study of massive stars in different metallicity environments is a central topic of current stellar research. The spectral analysis of massive stars requires adequate model atmospheres. The computation of such models is difficult and time-consuming. ... More
Resource Oblivious Sorting on MulticoresAug 06 2015We present a deterministic sorting algorithm, SPMS (Sample, Partition, and Merge Sort), that interleaves the partitioning of a sample sort with merging. Sequentially, it sorts $n$ elements in $O(n \log n)$ time cache-obliviously with an optimal number ... More
Fine-Grained Complexity and Conditional Hardness for Sparse GraphsNov 21 2016There is a large class of path and cycle problems on graphs that currently have $\tilde{O}(n^3)$ time algorithms. Graphs encountered in practice are typically sparse, with $m <<n^2$, were $n$ and $m$ are the number of vertices and edges in the graph. ... More
Resource Oblivious Sorting on MulticoresAug 06 2015Nov 02 2017We present a deterministic sorting algorithm, SPMS (Sample, Partition, and Merge Sort), that interleaves the partitioning of a sample sort with merging. Sequentially, it sorts $n$ elements in $O(n \log n)$ time cache-obliviously with an optimal number ... More
Harnack inequality for non-local Schrödinger operatorsJul 27 2015Sep 07 2017Let $x \in \mathbb{R}^d$, $d \geq 3,$ and $f: \mathbb{R}^d \rightarrow \mathbb{R}$ be a twice differentiable function with all second partial derivatives being continuous. For $1\leq i,j \leq d$, let $a_{ij} : \mathbb{R}^d \rightarrow \mathbb{R}$ be a ... More
Variable Instruction Fetch Rate to Reduce Control Dependent PenaltiesJul 14 2017In order to overcome the branch execution penalties of hard-to-predict instruction branches, two new instruction fetch micro-architectural methods are proposed in this paper. In addition, to compare performance of the two proposed methods, different instruction ... More
Distributed Algorithms for Directed Betweenness Centrality and All Pairs Shortest PathsMay 21 2018Feb 04 2019The betweenness centrality (BC) of a node in a network (or graph) is a measure of its importance in the network. BC is widely used in a large number of environments such as social networks, transport networks, security/mobile networks and more. We present ... More
A modified greedy algorithm to improve bounds for the vertex cover numberJan 03 2019In any attempt at designing an efficient algorithm for the minimum vertex cover problem, obtaining good upper and lower bounds for the vertex cover number could be crucial. In this article we present a modified greedy algorithm of worst-case time complexity ... More
Effective Floquet Hamiltonian theory of multiple-quantum NMR in anisotropic solids involving quadrupolar spins: Challenges and PerspectivesJun 28 2017The response of a quadrupolar nucleus (nuclear spin with I>1/2) to an oscillating radio-frequency (RF) pulse/field is delicately dependent on the ratio of the quadrupolar coupling constant to the amplitude of the pulse in addition to its duration and ... More
Backprop EvolutionAug 08 2018The back-propagation algorithm is the cornerstone of deep learning. Despite its importance, few variations of the algorithm have been attempted. This work presents an approach to discover new variations of the back-propagation equation. We use a domain ... More
Pulsar "Drifting"-Subpulse Polarization: No Evidence for Systematic Polarization-Angle RotationsNov 01 2001Polarization-angle density displays are given for pulsars B0809+74 and B2303+30, which exhibit no evidence of the systematic polarization-angle rotation within individual subpulses previously reported for these two stars. The ``drifting'' subpulses of ... More
SPH Entropy Errors and the Pressure BlipNov 09 2013Mar 03 2014The spurious pressure jump at a contact discontinuity, in SPH simulations of the compressible Euler equations is investigated. From the spatiotemporal behaviour of the error, the SPH pressure jump is likened to entropy errors observed for artificial viscosity ... More
Mayavi: a package for 3D visualization of scientific dataOct 23 2010Mayavi is an open-source, general-purpose, 3D scientific visualization package. It seeks to provide easy and interactive tools for data visualization that fit with the scientific user's workflow. For this purpose, Mayavi provides several entry points: ... More
Elementary construction of subharmonic exhaustion functionsMay 27 2004By a theorem of Greene and Wu, a noncompact connected Riemannian manifold admits a smooth strictly subharmonic exhaustion function. Demailly provided an elementary proof of this fact. A further simplification of Demailly's proof and some (mostly known) ... More
Finite dimensional imbeddings of harmonic spacesMar 23 1996In a noncompact harmonic manifold $M$ we establish finite dimensionality of the eigenspaces $V_{\lambda}$ generated by radial eigenfunctions of the form $\cosh r + c$. As a consequence, for such harmonic manifolds, we give an isometric imbedding of $M$ ... More
Finding $k$ Simple Shortest Paths and CyclesDec 07 2015Feb 23 2016The problem of finding multiple simple shortest paths in a weighted directed graph $G=(V,E)$ has many applications, and is considerably more difficult than the corresponding problem when cycles are allowed in the paths. Even for a single source-sink pair, ... More
Analysis of Randomized Work Stealing with False SharingMar 21 2011This paper analyzes the cache miss cost of algorithms when scheduled using randomized work stealing (RWS) in a parallel environment, taking into account the effects of false sharing. First, prior analyses (due to Acar et al.) are extended to incorporate ... More
Motivic complexes and special values of zeta functionsNov 13 2013Beginning with the conjecture of Artin and Tate in 1966, there has been a series of successively more general conjectures expressing the special values of the zeta function of an algebraic variety over a finite field in terms of other invariants of the ... More
Landau Levels in the noncommutative $AdS_2$Nov 22 2001Feb 15 2002We formulate the Landau problem in the context of the noncommutative analog of a surface of constant negative curvature, that is $AdS_2$ surface, and obtain the spectrum and contrast the same with the Landau levels one finds in the case of the commutative ... More
Fill Radius and the Fundamental GroupJun 24 2009Jul 27 2009In this note we relate the geometric notion of fill radius with the fundamental group of the manifold. We prove: ''Suppose that a closed Riemannian manifold M satisfies the property that its universal cover has bounded fill radius. Then the fundamental ... More
Null-induced mode changes in PSR B0809+74Feb 26 2002May 02 2002We have found that there are two distinct emission modes in PSR B0809+74. Beside its normal and most common mode, the pulsar emits in a significantly different quasi-stable mode after most or possibly all nulls, occasionally for over 100 pulses. In this ... More
Harmonic manifolds with some specific volume densitiesMar 24 1996We show that noncompact simply connected harmonic manifolds with volume density $\Theta_{p}(r) =\sinh ^{n-1} r$ is isometric to the real hyperbolic space and noncompact simply connected K\"{a}hler harmonic manifold with volume density $\Theta_{p}(r) =\sinh ... More
L^2 Castelnuovo-de Franchis, the cup product lemma, and filtered ends of Kaehler manifoldsNov 07 2007Simple approaches to the proofs of the L^2 Castelnuovo-de Franchis theorem and the cup product lemma which give new versions are developed. For example, suppose u and v are two linearly independent closed holomorphic 1-forms on a bounded geometry connected ... More
Equidistribution of zeros of random polynomialsJul 11 2016We study the asymptotic distribution of zeros for the random polynomials $P_n(z) = \sum_{k=0}^n A_k B_k(z)$, where $\{A_k\}_{k=0}^{\infty}$ are non-trivial i.i.d. complex random variables. Polynomials $\{B_k\}_{k=0}^{\infty}$ are deterministic, and are ... More
A Deterministic Distributed Algorithm for Weighted All Pairs Shortest Paths Through PipeliningJul 23 2018Oct 22 2018We present a new pipelined approach to compute all pairs shortest paths (APSP) in a directed graph with nonnegative integer edge weights (including zero weights) in the CONGEST model in the distributed setting. Our deterministic distributed algorithm ... More
Fine-Grained Complexity and Conditional Hardness for Sparse GraphsNov 21 2016Oct 19 2017We consider the fine-grained complexity of sparse graph problems that currently have $\tilde{O}(mn)$ time algorithms, where m is the number of edges and n is the number of vertices in the input graph. This class includes several important path problems ... More
The sinusoid and the phasorJun 08 2010Jun 10 2010Mathieu equation is widely used to study several natural phenomenon. In this paper, we show that replacing the sinusoid in the Mathieu equation with a phasor can lead to solutions that behave in a totally different way. Solutions of Mathieu equation are ... More
An upper bound for the clique number using clique ceiling numbersJun 03 2019In this article we present the idea of clique ceiling numbers of the vertices of a given graph that has a universal vertex. We follow up with a polynomial-time algorithm to compute an upper bound for the clique number of such a graph using clique ceiling ... More
Harnack inequality for non-local Schrödinger operatorsJul 27 2015Apr 14 2016Let $x \in \mathbb{R}^d$, $d \geq 3,$ and $f: \mathbb{R}^d \rightarrow \mathbb{R}$ be a twice differentiable function with all second partial derivatives being continuous. For $1\leq i,j \leq d$, let $a_{ij} : \mathbb{R}^d \rightarrow \mathbb{R}$ be a ... More
Hydrodynamic coupling between two fluid membranesJan 17 2011The coupled in-plane diffusion dynamics between point-particles embedded in stacked fluid membranes are investigated. We calculate the contributions to the coupling longitudinal and transverse diffusion coefficients due to particle motion within the different ... More
Exponentiation of motivic measuresDec 04 2014In this short note we establish some properties of all those motivic measures which can be exponentiated. As a first application, we show that the rationality of Kapranov's zeta function is stable under products. As a second application, we give an elementary ... More