Results for "Vassilis Kostakos"

total 319took 0.13s
Towards sustainable transport: wireless detection of passenger trips on public transport busesJun 04 2008Aug 08 2008An important problem in creating efficient public transport is obtaining data about the set of trips that passengers make, usually referred to as an Origin/Destination (OD) matrix. Obtaining this data is problematic and expensive in general, especially ... More
Size matters: performance declines if your pixels are too big or too smallApr 18 2008We present a conceptual model that describes the effect of pixel size on target acquisition. We demonstrate the use of our conceptual model by applying it to predict and explain the results of an experiment to evaluate users' performance in a target acquisition ... More
Correlating Pedestrian Flows and Search Engine QueriesJun 19 2012An important challenge for ubiquitous computing is the development of techniques that can characterize a location vis-a-vis the richness and diversity of urban settings. In this paper we report our work on correlating urban pedestrian flows with Google ... More
Situationally-Induced Impairments and Disabilities ResearchApr 12 2019Research has shown that various environmental factors impact smartphone interaction and lead to Situationally-Induced Impairments and Disabilities. In this work we discuss the importance of thoroughly understanding the effects of these situational impairments ... More
Smartphone App Usage Prediction Using Points of InterestNov 26 2017In this paper we present the first population-level, city-scale analysis of application usage on smartphones. Using deep packet inspection at the network operator level, we obtained a geo-tagged dataset with more than 6 million unique devices that launched ... More
Renormalized perturbation theory flow equations for the Anderson impurity modelJun 12 2014We apply the renormalized perturbation theory (RPT) to the symmetric Anderson impurity model. Within the RPT framework exact results for physical observables such as the spin and charge susceptibility can be obtained in terms of the renormalized values ... More
Chronological operator-valued Feynman-Kac formulae for generalized fractional evolutionsMay 23 2017We study the generalized fractional linear problem $D^{\nu}_{a+*} f(x) =A(x)f(x)+g(x)$, where $D^{\nu}$ is an arbitrary mixture of Caputo derivatives of order at most one and $A(x)$ a family of operators in a Banach space generating strongly continuous ... More
How to learn a graph from smooth signalsJan 11 2016We propose a framework that learns the graph structure underlying a set of smooth signals. Given $X\in\mathbb{R}^{m\times n}$ whose rows reside on the vertices of an unknown graph, we learn the edge weights $w\in\mathbb{R}_+^{m(m-1)/2}$ under the smoothness ... More
The Central Limit Theorem for the Smoluchovski Coagulation ModelAug 02 2007The general model of coagulation is considered. For basic classes of unbounded coagulation kernels the central limit theorem (CLT) is obtained for the fluctuations around the dynamic law of large numbers (LLN). A rather precise rate of convergence is ... More
Numerical integration of discontinuous functions in many dimensionsJun 05 2014We consider the problem of numerically integrating functions with hyperplane discontinuities over the entire Euclidean space in many dimensions. We describe a simple process through which the Euclidean space is partitioned into simplices on which the ... More
An extension of the disc AlgebraSep 27 2010We identify all uniform limits of polynomials on the closed unit disc with respect to the chordal metric \c{hi} . One such limit is f=oo. The other limits are holomorphic functions f:-->C so that for every {\zeta} in the boundary of unit disc D the limf(z) ... More
Stochastic monotonicity and duality for one-dimensional Markov processesFeb 25 2010Apr 29 2010The theory of monotonicity and duality is developed for general one-dimensional Feller processes. Moreover it is shown that local monotonicity conditions (conditions on the L\'evy kernel) are sufficient to prove the well-posedness of the corresponding ... More
Stochastic monotonicity and duality of $k$th order with application to put-call symmetry of powered optionsMay 15 2014We introduce a notion of $k$th order stochastic monotonicity and duality that allows one to unify the notion used in insurance mathematics (sometimes refereed to as Siegmund's duality) for the study of ruin probability and the duality responsible for ... More
On fully mixed and multidimensional extensions of the Caputo and Riemann-Liouville derivatives, related Markov processes and fractional differential equationsJan 16 2015From the point of view of stochastic analysis the Caputo and Riemann-Liouville derivatives of order $\al \in (0,2)$ can be viewed as (regularized) generators of stable L\'evy motions interrupted on crossing a boundary. This interpretation naturally suggests ... More
Asymptotic results for random coefficient bifurcating autoregressive processesApr 13 2012May 25 2013The purpose of this paper is to study the asymptotic behavior of the weighted least square estimators of the unknown parameters of random coefficient bifurcating autoregressive processes. Under suitable assumptions on the immigration and the inheritance, ... More
Game theoretic analysis of incomplete markets: emergence of probabilities, nonlinear and fractional Black-Scholes equationsMay 16 2011Expanding the ideas of the author's paper 'Nonexpansive maps and option pricing theory' (Kibernetica 34:6 (1998), 713-724) we develop a pure game-theoretic approach to option pricing, by-passing stochastic modeling. Risk neutral probabilities emerge automatically ... More
Limit theorems for bifurcating integer-valued autoregressive processesFeb 02 2012We study the asymptotic behavior of the weighted least squares estimators of the unknown parameters of bifurcating integer-valued autoregressive processes. Under suitable assumptions on the immigration, we establish the almost sure convergence of our ... More
Non-Existence of phase-shift breathers in one-dimensional Klein-Gordon lattices with nearest-neighbor interactionsApr 22 2012May 22 2013It is well known that one-dimensional Klein-Gordon lattices with nearest-neighbor interactions can support multibreathers with phase differences between the successive "central" oscillators $\phi_i=0\ \mbox{or}\ \pi$ (standard configurations). In this ... More
The evolutionary game of pressure (or interference), resistance and collaborationDec 03 2014Nov 20 2015In this paper we extend the framework of evolutionary inspection game put forward recently by the author and coworkers to a large class of conflict interactions dealing with the pressure executed by the major player (or principal) on the large group of ... More
Radial pulsations of neutron stars: computing alternative polytropic models regarding density and adiabatic indexJun 14 2014We revisit the problem of radial pulsations of neutron stars by computing four general-relativistic polytropic models, in which "density" and "adiabatic index" are involved with their discrete meanings: (i) "rest-mass density" or (ii) "mass-energy density" ... More
Lorentz-invariant and Lorentz-non-invariant aspects of a scalar tachyon field Lagrangian and the scalar tachyon Feynman propagatorMay 05 2016Jun 14 2016As it is well known, a consistent theory of faster-than-light particles (tachyons) can be built within the Lorentz-non-invariant approach only, invoking a concept of the preferred reference frame. This is a mandatory condition imposed by the requirement ... More
Generalized Continuous-Time Random Walks (CTRW), Subordination by Hitting Times and Fractional DynamicsJun 13 2007Functional limit theorem for continuous-time random walks (CTRW) are found in general case of dependent waiting times and jump sizes that are also position dependent. The limiting anomalous diffusion is described in terms of fractional dynamics. Probabilistic ... More
Separatrix splitting at a Hamiltonian $0^2 iω$ bifurcationSep 10 2014We discuss the splitting of a separatrix in a generic unfolding of a degenerate equilibrium in a Hamiltonian system with two degrees of freedom. We assume that the unperturbed fixed point has two purely imaginary eigenvalues and a double zero one. It ... More
Rank of mapping tori and companion matricesApr 15 2010Given $f$ in $GL(d,Z)$, it is decidable whether its mapping torus (the semi-direct product of $Z^d$ with $Z$) may be generated by two elements or not; if so, one can classify generating pairs up to Nielsen equivalence. If $f$ has infinite order, the mapping ... More
Inverse scattering on the line for a generalized nonlinear Schroedinger equationFeb 10 2004A one-dimensional generalized nonlinear Schroedinger equation is considered, and the corresponding inverse scattering problem is analyzed when the potential is compactly supported and depends on the wave function. The unique recovery of the potential ... More
The profile of a nonstandard Higgs boson at the LHCFeb 10 1995In a wide class of extensions of the Standard Model there is a scalar resonance with the quantum numbers of the usual Higgs boson but with different couplings to fermions and gauge bosons. Using an effective Lagrangian description, we examine the phenomenology ... More
Selective Unsupervised Feature Learning with Convolutional Neural Network (S-CNN)Jun 07 2016Supervised learning of convolutional neural networks (CNNs) can require very large amounts of labeled data. Labeling thousands or millions of training examples can be extremely time consuming and costly. One direction towards addressing this problem is ... More
Examining the Capability of GANs to Replace Real Biomedical Images in Classification Models TrainingApr 18 2019In this paper, we explore the possibility of generating artificial biomedical images that can be used as a substitute for real image datasets in applied machine learning tasks. We are focusing on generation of realistic chest X-ray images as well as on ... More
On filling families of finite subsets of the Cantor setMay 14 2008Let $\ee>0$ and $\fff$ be a family of finite subsets of the Cantor set $\ccc$. Following D. H. Fremlin, we say that $\fff$ is $\ee$-filling over $\ccc$ if $\fff$ is hereditary and for every $F\subseteq\ccc$ finite there exists $G\subseteq F$ such that ... More
Asymptotic series for the splitting of separatrices near a Hamiltonian bifurcationJun 14 2008This is a proof of an asymptotic formula which describes exponentially small splitting of separatrices in a generic analytic family of area-preserving maps near a Hamiltonian saddle-centre bifurcation. As a particular case and in combination with an earlier ... More
The Lévy-Khintchine type operators with variable Lipschitz continuous coefficients generate linear or nonlinear Markov processes and semigroupsNov 30 2009Ito's construction of Markovian solutions to stochastic equations driven by a L\'evy noise is extended to nonlinear distribution dependent integrands aiming at the effective construction of linear and nonlinear Markov semigroups and the corresponding ... More
Sensitivity analysis for HJB equations with an application to coupled backward-forward systemsMar 25 2013Jul 29 2015In this paper, we analyse Lipschitz continuous dependence of the solution to Hamilton-Jacobi-Bellman equations on a functional parameter. This sensitivity analysis not only has the interest on its own, but also is important for the mean field games methodology, ... More
Measure and integration on Boolean algebras of regular open subsets in a topological spaceMar 07 2017The regular open subsets of a topological space form a Boolean algebra, where the `join' of two regular open sets is the interior of the closure of their union. A `credence' is a finitely additive probability measure on this Boolean algebra, or on one ... More
A Rademacher-Menchov approach for random coefficient bifurcating autoregressive processesOct 22 2012We investigate the asymptotic behavior of the least squares estimator of the unknown parameters of random coefficient bifurcating autoregressive processes. Under suitable assumptions on inherited and environmental effects, we establish the almost sure ... More
Regularity and Sensitivity for McKean-Vlasov Type SPDEs Generated by Stable-like ProcessesAug 13 2018In this paper we study the sensitivity of nonlinear stochastic differential equations of McKean-Vlasov type generated by stable-like processes. By using the method of stochastic characteristics, we transfer these equations to the non-stochastic equations ... More
Uniformity norms, their weaker versions, and applicationsOct 03 2016Oct 09 2016We show that, under some mild hypotheses, the Gowers uniformity norms (both in the additive and in the hypergraph setting) are essentially equivalent to certain weaker norms which are easier to understand. We present two applications of this equivalence: ... More
Padé Approximants, density of rational functions in $\bbb{A^\infty(\OO)}$ and smoothness of the integration operatorDec 18 2012First we establish some generic universalities for Pad\'{e} approximants in the closure $X^\infty(\OO)$ in $A^\infty(\OO)$ of all rational functions with poles off $\oO$, the closure taken in $\C$ of the domain $\OO\subset\C$.\ Next we give sufficient ... More
Non-Stationary Dividend-Price RatiosFeb 16 2019Dividend yields have been widely used in previous research to relate stock market valuations to cash flow fundamentals. However, this approach relies on the assumption that dividend yields are stationary. Due to the failure to reject the hypothesis of ... More
Arc length as a conformal parameter for locally analytic curvesAug 31 2015For any locally analytic curve we show that arc length can be complexified and seen as a conformal parameter. As an application, we show that any such curve defines a unique maximal one and that the notions of analytic Jordan curve coincides with the ... More
Interpolating vector fields for near identity maps and averagingNov 06 2017For a smooth near identity map, we introduce the notion of an interpolating vector field written in terms of iterates of the map. Our construction is based on Lagrangian interpolation and provides an explicit expressions for autonomous vector fields which ... More
Width of homoclinic zone for quadratic mapsMay 02 2008We study several families of planar quadratic diffeomorphisms near a Bogdanov-Takens bifurcation. For each family, the associate bifurcation diagram can be deduced from the interpolating flow. However, a zone of chaos confined between two lines of homoclinic ... More
An Arctangent LawFeb 16 2016Let $M_r$ be the maximum value of an one-dimensional Brownian motion on the (time) interval $[0, r]$. We derive an explicit formula for the distribution of the time required (after $r$) for the Brownian motion to exceed $M_r$.
The turnpike theorems for Markov gamesMar 29 2012This paper has a two-folded purpose. First, we attempt to outline the development of the turnpike theorems in the the last several decades. Second, we study turnpike theorems in finite-horizon two-person zero-sum Markov games on a general Borel state ... More
Existence of solutions to path-dependent kinetic equations and related forward - backward systemsMar 21 2013This paper is devoted to path-dependent kinetics equations arising, in particular, from the analysis of the coupled backward - forward systems of equations of mean field games. We present local well-posedness, global existence and some regularity results ... More
On pairs of definable orthogonal familiesMay 14 2008We introduce the notion of an M-family of infinite subsets of $\nn$ which is implicitly contained in the work of A. R. D. Mathias. We study the structure of a pair of orthogonal hereditary families $\aaa$ and $\bbb$, where $\aaa$ is analytic and $\bbb$ ... More
Weighted Efficient Domination for $(P_5+kP_2)$-Free Graphs in Polynomial TimeJul 17 2014Let $G$ be a finite undirected graph. A vertex {\em dominates} itself and all its neighbors in $G$. A vertex set $D$ is an {\em efficient dominating set} (\emph{e.d.}\ for short) of $G$ if every vertex of $G$ is dominated by exactly one vertex of $D$. ... More
Patterns of consumption in socio-economic models with heterogeneous interacting agentsSep 09 1999We study consumption behaviour in systems with heterogeneous interacting agents. Two different models are introduced, respectively with long and short range interactions among agents. At any time step an agent decides whether or not to consume a good, ... More
Comment on "The Phenomenology of a Nonstandard Higgs Boson in W_L W_L Scattering"Sep 03 1994We show that in Composite Higgs models, the coupling of the Higgs resonance to a pair of $W$ bosons is weaker than the corresponding Standard Model coupling, provided the Higgs arises from electroweak doublets only. This is partly due to the effects of ... More
Nonlinear diffusions and stable-like processes with coefficients depending on the median or VaRJul 25 2012In June 2012 on a conference in Bielefeld, after the author made the presentation of his theory of nonlinear Markov processes, Tom Kurtz asked him whether his methods would allow to get well-posedness for nonlinear McKean-Vlasov type diffusions with coefficients ... More
On the mean field games with common noise and the McKean-Vlasov SPDEsJun 15 2015We formulate the MFG limit for $N$ interacting agents with a common noise as a single quasi-linear deterministic infinite-dimensional partial differential second order backward equation. We prove that any its (regular enough) solution provides an $1/N$-Nash-equilibrium ... More
Inspection games in a mean field settingJul 29 2015In this paper, we present a new development of inspection games in a mean field setting. In our dynamic version of an inspection game, there is one inspector and a large number N interacting inspectees with a finite state space. By applying the mean field ... More
Influence of Control Parameters and the Size of Biomedical Image Datasets on the Success of Adversarial AttacksApr 15 2019In this paper, we study dependence of the success rate of adversarial attacks to the Deep Neural Networks on the biomedical image type, control parameters, and image dataset size. With this work, we are going to contribute towards accumulation of experimental ... More
Mean-field-game model for Botnet defense in Cyber-securityNov 20 2015We initiate the analysis of the response of computer owners to various offers of defence systems against a cyber-hacker (for instance, a botnet attack), as a stochastic game of a large number of interacting agents. We introduce a simple mean-field game ... More
White Paper: Brief overview of current practices for open consultationMay 09 2016The purpose of this document is to provide a brief overview of open consultation approaches in the current, international setting and propose a role for Information Technologies (IT) as a disruptive force in this setting.
How to implant a causal $Θ$ function into a tachyon field operatorOct 29 2015May 05 2016The preferred reference frame in which the signal propagation is governed by retarded causality is a must for any theory of faster-than-light particles and signals. It is shown in the previous papers of the author that such a system does exist and is ... More
Traveling Waves of Discrete Nonlinear Schrodinger Equations with Nonlocal InteractionsSep 09 2009Existence and bifurcation results are derived for quasi periodic traveling waves of discrete nonlinear Schrodinger equations with nonlocal interactions and with polynomial type potentials. Variational tools are used. Several concrete nonlocal interactions ... More
Nonlinear Lévy and nonlinear Feller processes: an analytic introductionMar 29 2011The program of studying general nonlinear Markov processes was put forward in V. N. Kolokoltsov "Nonlinear Markov Semigroups and Interacting L\'evy Type Processes" (Journ. Stat. Physics 126:3 (2007), 585-642), and was developed by the author in monograph ... More
Stochastic duality of Markov processes: a study via generatorsApr 05 2013The paper is devoted to a systematic study of the duality of processes in the sense that $E f(X_t^x,y)=E f (x, Y_t^y)$ for a certain $f$. This classical topic has well known applications in interacting particles, intertwining, superprocesses, stochastic ... More
Patterns of consumption in a discrete choice model with asymmetric interactionsOct 30 2000Oct 31 2000We study the consumption behaviour of an asymmetric network of heterogeneous agents in the framework of discrete choice models with stochastic decision rules. We assume that the interactions among agents are uniquely specified by their ``social distance'' ... More
Quasi-radial modes of pulsating neutron stars: numerical results for general-relativistic rigidly rotating polytropic modelsJun 12 2014Oct 12 2014In this paper we compute general-relativistic polytropic models simulating rigidly rotating, pulsating neutron stars. These relativistic compact objects, with a radius of $\sim 10 \, \mathrm{km}$ and mass between $\sim 1.4$ and $3.2$ solar masses, are ... More
Simplified normal forms near a degenerate elliptic fixed point in two-parametric families of area-preserving mapsDec 20 2013We derive simplified normal forms for an area-preserving map in a neighbourhood of a degenerate resonant elliptic fixed point. Such fixed points appear in generic two-parameter families of area-preserving maps. We also derive a simplified normal form ... More
Some Results on Ordinary Differential Operators with Periodic CoefficientsDec 14 2014Jan 15 2015For a general ordinary differential operator $\mathcal{L}$ with periodic coefficients we prove that the characteristic polynomial of the Floquet matrix is irreducible over the field of meromorphic functions. We also consider a multipoint eigenvalue problem ... More
The Eulerian distribution on the involutions of the hyperoctahedral group is unimodalJan 22 2018The Eulerian distribution on the involutions of the symmetric group is unimodal, as shown by Guo and Zeng. In this paper we prove that the Eulerian distribution on the involutions of the hyperoctahedral group, when viewed as a colored permutation group, ... More
Similarity Solutions of a Replicator Dynamics Equation Associated to a Continuum of Pure StrategiesDec 14 2014We introduce a nonlinear degenerate parabolic equation containing a nonlocal term. The equation serves as a replicator dynamics model where the set of strategies is a continuum. In our model the payoff operator (which is the continuous analog of the payoff ... More
Optimal Scheduling of Water Distribution SystemsJun 20 2018With dynamic electricity pricing, the operation of water distribution systems (WDS) is expected to become more variable. The pumps moving water from reservoirs to tanks and consumers can serve as energy storage alternatives if properly operated. Nevertheless, ... More
Three-body gravitino decays in the MSSMMay 29 2013Jul 12 2013We present results from a new calculation of two- and three-body decays of the gravitino including all possible Feynman graphs. The work is done in the R-parity conserving Minimal Supersymmetric Standard Model, assuming that the gravitino is unstable. ... More
Experimental Prospects for CP Violation in CharmSep 15 1998Jan 07 1999Experimental sensitivity to CP violation in charm decay is beginning to approach the interesting regime ($\sim10^{-3}$) in which new physics may be manifest. In the early years of the 21st century, if the technical challenges can be met, the proposed ... More
Modifying the optical path in a nonlinear double-slit experimentOct 15 2015In this letter, we study a nonlinear interferometric setup based on diffraction rather than beam combining. It consists of a nonlinear analogue of Young's double-slit experiment where a nonlinear material is placed exactly after one of the slits. The ... More
Distributed Robust Power System State EstimationApr 04 2012Jun 30 2012Deregulation of energy markets, penetration of renewables, advanced metering capabilities, and the urge for situational awareness, all call for system-wide power system state estimation (PSSE). Implementing a centralized estimator though is practically ... More
An Ultrahigh-Statistics Charm Experiment for the Year $\sim2000$May 03 1995After reviewing the motivation for high-statistics charm studies, we describe a fixed-target experiment capable of reconstructing $>10^8$ charm decays. Such an experiment can test the Standard Model and probe non-Standard physics through sensitive searches ... More
GravitinoPack and decays of supersymmetric metastable particlesSep 30 2015We present the package GravitinoPack that calculates the two- and three-body decays of unstable supersymmetric particles involving the gravitino in the final or initial state. In a previous paper, we already showed results for the gravitino decays into ... More
Universal Taylor Series On Convex Subsets Of $\Mathbb{C}^{N}$Feb 17 2013We prove the existence of holomorphic functions $f$ defined on any open convex subset ${\rm \Omega}\subset {{\mathbb C}}^n$, whose partial sums of the Taylor developments approximate uniformly any complex polynomial on any convex compact set disjoint ... More
Transmission eigenvalues for the selfadjoint Schrödinger operator on the half lineApr 09 2014The transmission eigenvalues corresponding to the half-line Schr\"odinger equation with the general selfadjoint boundary condition is analyzed when the potential is real valued, integrable, and compactly supported. It is shown that a transmission eigenvalue ... More
Reconstruction of the wave speed from transmission eigenvalues for the spherically-symmetric variable-speed wave equationApr 22 2013The unique reconstruction of a spherically-symmetric wave speed $v$ is considered in a bounded spherical region of radius $b$ from the set of corresponding transmission eigenvalues for which the corresponding eigenfunctions are also spherically symmetric. ... More
The last integrable case of kozlov-Treshchev Birkhoff integrable potentialsJan 10 2007We establish the integrability of the last open case in the Kozlov-Treshchev classification of Birkhoff integrable Hamiltonian systems. The technique used is a modification of the so called quadratic Lax pair for $D_n$ Toda lattice combined with a method ... More
From Sparse Signals to Sparse Residuals for Robust SensingNov 01 2010Mar 27 2011One of the key challenges in sensor networks is the extraction of information by fusing data from a multitude of distinct, but possibly unreliable sensors. Recovering information from the maximum number of dependable sensors while specifying the unreliable ... More
The Phenomenology of a Non-Standard Higgs Boson IN $W_{L}W_{L}$ ScatteringDec 21 1993Jan 07 1994In this paper we consider the phenomenology of a ``non-standard'' Higgs Boson in longitudinal gauge-Boson scattering. First, we present a composite Higgs model (based on an $SU(4)/Sp\,(4)$ chiral-symmetry breaking pattern) in which there is a non-standard ... More
High-order terms in the renormalized perturbation theory for the Anderson impurity modelMar 12 2015We study the renormalized perturbation theory of the single-impurity Anderson model, particularly the high-order terms in the expansion of the self-energy in powers of the renormalized coupling $\tilde{U}$. Though the presence of counter-terms in the ... More
Analytic results for the Anderson Impurity ModelDec 17 2014In the Renormalised Perturbation Theory (RPT) the Anderson impurity model is interpreted in terms of renormalised parameters $\boldsymbol{\tilde{\mu}}= (\tilde{\epsilon}_d, \tilde{\Delta}, \tilde{U})$ which are in a one-to-one correspondence with the ... More
GravitinoPack and late decays involving gravitinosOct 12 2015In this talk, we present the package GravitinoPack that calculates decays of unstable supersymmetric particles, involving gravitinos in the final or initial state. If the gravitino is the dark matter particle and therefore stable, the package calculates ... More
Evolutionary game of coalition building under external pressureMay 23 2017We study the fragmentation-coagulation (or merging and splitting) evolutionary control model as introduced recently by one of the authors, where $N$ small players can form coalitions to resist to the pressure exerted by the principal. It is a Markov chain ... More
On the Flow Problem in Water Distribution Networks: Uniqueness and SolversJan 11 2019Increasing concerns on the security and quality of water distribution systems (WDS), along with their role as smart city components, call for computational tools with performance guarantees. To this end, this work revisits the physical laws governing ... More
Positve Entropy Geodesic Flows on NilmanifoldsSep 28 2007Let T be the nilpotent group of 4 x 4 real upper triangular matrices. In this note we show that the Euler equations of certain left-invariant riemannian metrics on T have a horseshoe. We also show, with the aid of a numerical computation of a Melnikov-type ... More
Universal Padé ApproximationFeb 23 2011In transferring some results from universal Taylor series to the case of Pad\'e approximants we obtain stronger results, such as, universal approximation on compact sets of arbitrary connectivity and generic results on planar domains of any connectivity ... More
Sparse Volterra and Polynomial Regression Models: Recoverability and EstimationMar 03 2011Sep 07 2011Volterra and polynomial regression models play a major role in nonlinear system identification and inference tasks. Exciting applications ranging from neuroscience to genome-wide association analysis build on these models with the additional requirement ... More
Travelling Waves in Hamiltonian Systems on 2D Lattices with Nearest Neighbor InteractionsJan 17 2007We study travelling waves on a two--dimensional lattice with linear and nonlinear coupling between nearest particles and a periodic nonlinear substrate potential. Such a discrete system can model molecules adsorbed on a substrate crystal surface. We show ... More
Phenomenology of a Non-Standard HiggsApr 23 1993May 03 1993The one-Higgs-doublet standard model is necessarily incomplete because of the triviality of the scalar symmetry-breaking sector. If the Higgs mass is approximately 600 GeV or higher, there must be additional dynamics at a scale $\Lambda$ which is less ... More
On the stability of multibreathers in Klein-Gordon chainsFeb 23 2009Jul 06 2009In the present paper, a theorem, which determines the linear stability of multibreathers in Klein-Gordon chains, is proven. Specifically, it is shown that for soft nonlinearities, and positive inter-site coupling, only structures with adjacent sites excited ... More
Inverse problem with transmission eigenvalues for the discrete Schrödinger equationJan 28 2015The discrete Schr\"odinger equation with the Dirichlet boundary condition is considered on a half-line lattice when the potential is real valued and compactly supported. The inverse problem of recovery of the potential from the so-called transmission ... More
Natural Gas Flow Equations: Uniqueness and an MI-SOCP SolverSep 24 2018The critical role of gas fired-plants to compensate renewable generation has increased the operational variability in natural gas networks (GN). Towards developing more reliable and efficient computational tools for GN monitoring, control, and planning, ... More
Splitting of separatrices for the Hamiltonian-Hopf bifurcation with the Swift-Hohenberg equation as an exampleApr 12 2010Apr 29 2013We study homoclinic orbits of the Swift-Hohenberg equation near a Hamiltonian-Hopf bifurcation. It is well known that in this case the normal form of the equation is integrable at all orders. Therefore the difference between the stable and unstable manifolds ... More
Online Energy Price Matrix Factorization for Power Grid Topology TrackingOct 22 2014Grid security and open markets are two major smart grid goals. Transparency of market data facilitates a competitive and efficient energy environment, yet it may also reveal critical physical system information. Recovering the grid topology based solely ... More
Incentives for Truthful Peer GradingApr 11 2016Peer grading systems work well only if users have incentives to grade truthfully. An example of non-truthful grading, that we observed in classrooms, consists in students assigning the maximum grade to all submissions. With a naive grading scheme, such ... More
Nonlinear magnetoinductive transmission linesJan 13 2011Power transmission in one-dimensional nonlinear magnetic metamaterials driven at one end is investigated numerically and analytically in a wide frequency range. The nonlinear magnetic metamaterials are composed of varactor-loaded split-ring resonators ... More
Measurable events indexed by wordsMar 19 2013Oct 22 2014For every integer $k\geq 2$ let $[k]^{<\mathbb{N}}$ be the set of all words over $k$, that is, all finite sequences having values in $[k]:=\{1,...,k\}$. A Carlson-Simpson tree of $[k]^{<\mathbb{N}}$ of dimension $m\geq 1$ is a subset of $[k]^{<\mathbb{N}}$ ... More
Szemerédi's regularity lemma via martingalesOct 22 2014Jul 22 2016We prove a variant of the abstract probabilistic version of Szemer\'edi's regularity lemma, due to Tao, which applies to a number of structures (including graphs, hypergraphs, hypercubes, graphons, and many more) and works for random variables in $L_p$ ... More
Measurable events indexed by products of treesSep 22 2012Jun 13 2013A tree $T$ is said to be homogeneous if it is uniquely rooted and there exists an integer $b\meg 2$, called the branching number of $T$, such that every $t\in T$ has exactly $b$ immediate successors. A vector homogeneous tree $\mathbf{T}$ is a finite ... More
A simple proof of the density Hales-Jewett theoremSep 22 2012Mar 19 2013We give a purely combinatorial proof of the density Hales--Jewett Theorem that is modeled after Polymath's proof but is significantly simpler. In particular, we avoid the use of the equal-slices measure and work exclusively with the uniform measure.
A parallel code for multiprecision computations of the Lane-Emden differential equationApr 27 2016We compute multiprecision solutions of the Lane-Emden equation. This differential equation arises when introducing the well-known polytropic model into the equation of hydrostatic equilibrium for a nondistorted star. Since such multiprecision computations ... More
An Approximate Nash Equilibrium for Pure Jump Markov Games of Mean-field-type on Continuous State SpaceMay 17 2016We investigate mean-field games from the point of view of a large number of indistinguishable players which eventually converges to infinity. The players are weakly coupled via their empirical measure. The dynamics of the states of the individual players ... More