Results for "Konstantinos Karampelas"

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Coronal loop transverse oscillations excited by different driver frequenciesMay 14 2019We analyse transverse oscillations of a coronal loop excited by continuous monoperiodic motions of the loop footpoint at different frequencies in the presence of gravity. Using the MPI-AMRVAC code, we perform three-dimensional numerical magnetohydrodynamic ... More
Wave heating in simulated multi-stranded coronal loopsJul 18 2019It has been found that the Kelvin-Helmholtz instability (KHI) induced by both transverse and torsional oscillations in coronal loops can reinforce the effects of wave heating. In this study, we model a coronal loop as a system of individual strands, and ... More
Wave heating in gravitationally stratified coronal loops in the presence of resistivity and viscosityJan 09 2019Jan 15 2019In recent years, coronal loops have been the focus of studies related to the damping of different magnetohydrodynamic (MHD) surface waves and their connection with coronal seismology and wave heating. For a better understanding of wave heating, we need ... More
The anisotropic λ-deformed SU(2) model is integrableDec 16 2014Jun 19 2015The all-loop anisotropic Thirring model interpolates between the WZW model and the non-Abelian T-dual of the anisotropic principal chiral model. We focus on the SU(2) case and we prove that it is classically integrable by providing its Lax pair formulation. ... More
A Converse to a Theorem on Normal Forms of Volume Forms with Respect to a HypersurfaceMay 31 2014In this note we give a positive answer to a question asked by Y. Colin de Verdi\`ere concerning the converse of the following theorem, due to A. N. Varchenko: two germs of volume forms are equivalent with respect to diffeomorphisms preserving a germ of ... More
Beyond the Dirac phase factor: Dynamical Quantum Phase-Nonlocalities in the Schrödinger PictureSep 08 2011Generalized solutions of the standard gauge transformation equations are presented and discussed in physical terms. They go beyond the usual Dirac phase factors and they exhibit nonlocal quantal behavior, with the well-known Relativistic Causality of ... More
Nonlocal Phases of Local Quantum Mechanical Wavefunctions in Static and Time-Dependent Aharonov-Bohm ExperimentsSep 17 2010We show that the standard Dirac phase factor is not the only solution of the gauge transformation equations. The full form of a general gauge function (that connects systems that move in different sets of scalar and vector potentials), apart from Dirac ... More
Steep Eternal Inflation and the SwamplandSep 19 2018Oct 18 2018I investigate whether eternal inflation is possible when the inflaton originally travels upslope the scalar potential and inevitably reaches a turn-around point where its classical kinetic energy momentarily vanishes. This behaviour occurs regardless ... More
Supergravity inspired Vector CurvatonMay 23 2007It is investigated whether a massive Abelian vector field, whose gauge kinetic function is growing during inflation, can be responsible for the generation of the curvature perturbation in the Universe. Particle production is studied and it is shown that ... More
Can a vector field be responsible for the curvature perturbation in the Universe?Jul 20 2006Sep 22 2006I investigate the possibility that the observed curvature perturbation is due to a massive vector field. To avoid generating a large scale anisotropy the vector field is not taken to be driving inflation. Instead it is assumed to become important after ... More
The quantum origin of cosmic structure: theory and observationsSep 28 2010Oct 13 2010The particle production process is reviewed, through which cosmic inflation can produce a scale invariant superhorizon spectrum of perturbations of suitable fields starting from their quantum fluctuations. Afterwards, in the context of the inflationary ... More
Non-asymptotic performance analysis of importance sampling schemes for small noise diffusionsOct 25 2013Jul 29 2014In this note we develop a prelimit analysis of performance measures for importance sampling schemes related to small noise diffusion processes. In importance sampling the performance of any change of measure is characterized by its second moment. For ... More
The Anatomy of the Three-Point Shot: Spatial Bias, Fractals and the Three-Point Line in the NBASep 11 2016Even though it might have taken some time, the three-point line ultimately changed the way the game is played as evidenced by the increase in the three-point shot attempts over the years. However, during the last few years we have experienced record-breaking ... More
Stability Analysis and Best Approximation Error Estimates of Discontinuous Time-Stepping Schemes for the Allen-Cahn EquationOct 17 2016Fully-discrete approximations of the Allen-Cahn equation are considered. In particular, we consider schemes of arbitrary order based on a discontinuous Galerkin (in time) approach combined with standard conforming finite elements (in space). We prove ... More
On the Medianwidth of GraphsDec 03 2015Jan 28 2016A median graph is a connected graph, such that for any three vertices $u,v,w$ there is exactly one vertex $x$ that lies simultaneously on a shortest $(u,v)$-path, a shortest $(v,w)$-path and a shortest $(w,u)$-path. Examples of median graphs are trees ... More
Beyond the Dirac phase factor: Dynamical Quantum Phase-Nonlocalities in the Schroedinger PictureApr 28 2011May 11 2011Generalized solutions of the standard gauge transformation equations are presented and discussed in physical terms. They go beyond the usual Dirac phase factors and they exhibit nonlocal quantal behavior, with the well-known Relativistic Causality of ... More
The Star Formation Law in a Multifractal ISMSep 10 2007The surface density of the star formation rate in different galaxies, as well as in different parts of a single galaxy, scales nonlinearly with the surface density of the total gas. This observationally established relation is known as the Kennicutt-Schmidt ... More
The Shapes of Molecular Cloud Cores in OrionMay 02 2007We investigate the intrinsic shapes of starless cores in the Orion GMC, using the prestellar core sample of Nutter and Ward-Thompson (2007), which is based on submillimeter SCUBA data. We employ a maximum-likelihood method to reconstruct the intrinsic ... More
Three experimental pearls in Costas arraysJun 22 2007The results of 3 experiments in Costas arrays are presented, for which theoretical explanation is still not available: the number of dots on the main diagonal of exponential Welch arrays, the parity populations of Golomb arrays generated in fields of ... More
Primitive recursive bounds for the finite version of Gowers' $c_0$ theoremJan 31 2014May 22 2015We provide primitive recursive bounds for the finite version of Gowers' $c_0$ theorem for both the positive and the general case. We also provide multidimensional versions of these results.
Diquark properties from lattice QCDOct 16 2005It has been argued recently that diquarks, a pair of quarks in the anti-triplet representation of SU(3) color, are important building blocks of baryons. The assumption that the scalar diquark is tightly bound seems to be nicely accommodated by experimental ... More
Large Deviations and Importance Sampling for Systems of Slow-Fast MotionFeb 27 2012Sep 18 2012In this paper we develop the large deviations principle and a rigorous mathematical framework for asymptotically efficient importance sampling schemes for general, fully dependent systems of stochastic differential equations of slow and fast motion with ... More
Ultra slow-roll inflation demystifiedJul 18 2017Nov 15 2017Ultra-slow-roll (USR) inflation is a new mode of inflation which corresponds to the occasions when the inflaton field must traverse an extremely flat part of the scalar potential, when the usual slow-roll (SR) fails. We investigate USR and obtain an estimate ... More
Trapped Quintessential Inflation from Flux CompactificationsFeb 01 2007Quintessential inflation is studied using a string modulus as the inflaton - quintessence field. It is assumed that the modulus crosses an enhanced symmetry point (ESP) in field space. Particle production at the ESP temporarily traps the modulus resulting ... More
Gradings, Braidings, Representations, Paraparticles: some open problemsOct 08 2012A long-term research proposal on the algebraic structure, the representations and the possible applications of paraparticle algebras is structured in three modules: The first part stems from an attempt to classify the inequivalent gradings and braided ... More
A new proof of Vantieghem's theoremOct 26 2014We present a new proof of a primality criterion first proved by Emmanuel Vantieghem.
Large Deviations Principle for a Large Class of One-Dimensional Markov ProcessesJun 16 2010Jul 16 2011We study the large deviations principle for one dimensional, continuous, homogeneous, strong Markov processes that do not necessarily behave locally as a Wiener process. Any strong Markov process $X_{t}$ in $\mathbb{R}$ that is continuous with probability ... More
Symmetrization of exterior parabolic problems and probabilistic interpretationApr 06 2016We prove a comparison theorem for the averages of the solutions of two exterior parabolic problems, the second being the "symmetrization" of the first one, by using approximation of the Schwarz symmetrization by polarizations, as it was introduced in ... More
On Finite difference schemes for partial integro-differential equations of Lévy typeAug 01 2016In this article we introduce a finite difference approximation for integro-differential operators of L\'evy type. We approximate solutions of integro-differential equations, where the second order operator is allowed to degenerate. In the existing literature, ... More
Combinatorial Structures on van der Waerden setsJan 18 2013Jun 20 2013In this paper we provide two results. The first one consists an infinitary version of the Furstenberg-Weiss Theorem. More precisely we show that every subset $A$ of a homogeneous tree $T$ such that $\frac{|A\cap T(n)|}{|T(n)|}\geq\delta$, where T(n) denotes ... More
Footballonomics: The Anatomy of American Football; Evidence from 7 years of NFL game dataJan 17 2016Feb 17 2016Do NFL teams make rational decisions? What factors potentially affect the probability of wining a game in NFL? How can a team come back from a demoralizing interception? In this study we begin by examining the hypothesis of rational coaching, that is, ... More
A Note on the Orderability of Dehn Fillings of the Manifold $v2503$Apr 16 2019We show that Dehn filling on the manifold $v2503$ results in a non-orderable space for all rational slopes in the interval $(-\infty , -1)$. This is consistent with the L-space conjecture, which predicts that all fillings will result in a non-orderable ... More
Statistical Anisotropy and the Vector Curvaton ParadigmJul 14 2011Apr 10 2012The vector curvaton paradigm is reviewed. The mechanism allows a massive vector boson field to contribute to or even generate the curvature perturbation in the Universe. Contribution of vector bosons is likely to generate statistical anisotropy in the ... More
Models of Quintessential InflationNov 27 2001A unified approach to quintessence and inflation is investigated with the use of a single scalar field. It is argued that successful potentials have to approximate a combination of exponential and inverse power-law decline in the limit of large values ... More
Shaft Inflation and the Planck satellite observationsOct 22 2015A new family of inflation models is introduced and studied. The models are characterised by a scalar potential which, far from the origin, approaches an inflationary plateau in a power-law manner, while near the origin becomes monomial, as in chaotic ... More
Shaft InflationMar 17 2014Jun 11 2014A new family of inflation models is introduced and studied. The models are characterised by a scalar potential which, far from the origin, approximates an inflationary plateau, while near the origin becomes monomial, as in chaotic inflation. The models ... More
Where galaxies really come fromJun 04 2009The fundamental paradox of the incompatibility of the observed large-scale uniformity of the Universe with the fact that the age of the Universe is finite is overcome by the introduction of an initial a period of superluminal expansion of space, called ... More
Galactic Magnetic Fields as a consequence of InflationMay 28 2001The generation of a magnetic field in the Early Universe is considered, due to the gravitational production of the Z-boson field during inflation. Scaled to the epoch of galaxy formation this magnetic field suffices to trigger the galactic dynamo and ... More
A Note on the Smoluchowski-Kramers Approximation for the Langevin Equation with ReflectionApr 18 2010According to the Smoluchowski-Kramers approximation, the solution of the equation ${\mu}\ddot{q}^{\mu}_t=b(q^{\mu}_t)-\dot{q}^{\mu}_t+{\Sigma}(q^{\mu}_t)\dot{W}_t, q^{\mu}_0=q, \dot{q}^{\mu}_0=p$ converges to the solution of the equation $\dot{q}_t=b(q_t)+{\Sigma}(q_t)\dot{W}_t, ... More
Series expansion of weighted Finsler-Kato-Hardy inequalitiesFeb 03 2019In this work, we consider weighted anisotropic Hardy inequalities and trace Hardy inequalities involving a general Finsler metric. We follow a unifying approach, by establishing first a sharp interpolation between them, extending the corresponding nonweighted ... More
Fluctuation analysis and short time asymptotics for multiple scales diffusion processesJun 06 2013Feb 18 2015We consider the limiting behavior of fluctuations of small noise diffusions with multiple scales around their homogenized deterministic limit. We allow full dependence of the coefficients on the slow and fast motion. These processes arise naturally when ... More
Rare event simulation for multiscale diffusions in random environmentsOct 01 2014Sep 28 2015We consider systems of stochastic differential equations with multiple scales and small noise and assume that the coefficients of the equations are ergodic and stationary random fields. Our goal is to construct provably-efficient importance sampling Monte ... More
Systemic Risk and Default Clustering for Large Financial SystemsFeb 21 2014Feb 18 2015As it is known in the finance risk and macroeconomics literature, risk-sharing in large portfolios may increase the probability of creation of default clusters and of systemic risk. We review recent developments on mathematical and computational tools ... More
Comparing two samples by penalized logistic regressionJul 16 2008Inference based on the penalized density ratio model is proposed and studied. The model under consideration is specified by assuming that the log--likelihood function of two unknown densities is of some parametric form. The model has been extended to ... More
Lower bound of the asymptotic complexity of self-similar fractal graphsOct 28 2015We study the asymptotic complexity constant of the sequence of approximating graphs to a fully symmetric self-similar structure on a finitely ramified fractal $K$. We show how full symmetry implies existence of the asymptotic complexity constant and obtain ... More
Search for a dileptonic edge with CMSOct 07 2014We present a search for a kinematic edge in the invariant mass distribution of two opposite-sign same-flavor leptons, in final states with jets and missing transverse energy. The analysis makes use of $19.4$ fb$^{-1}$ proton-proton collision data at $\sqrt{s} ... More
An infinite collection of quartic polynomials whose products of consecutive values are not perfect squaresOct 04 2016Using an elementary identity, we prove that for infinitely many polynomials $P(x)\in \mathbb{Z}[X]$ of fourth degree, the equation $\prod\limits_{k=1}^{n}P(k)=y^2$ has finitely many solutions in $\mathbb{Z}$. We also give an example of a quartic polynomial ... More
On colorings of variable wordsSep 04 2014In this note, we prove that the base case of the Graham--Rothschild Theorem, i.e., the one that considers colorings of the ($1$-dimensional) variable words, admits bounds in the class $\mathcal{E}^5$ of Grzegorczyk's hierarchy.
Density Perturbations in the Universe from Massive Vector FieldsSep 07 2007I discuss the possibility of using a massive vector field to generate the density perturbation in the Universe. I find that a scale-invariant superhorizon spectrum of vector field perturbations is possible to generate during inflation. The associated ... More
Modular Hybrid Inflation without Flat Directions and the CurvatonAug 06 2004I study two-stage hybrid inflation driven by moduli fields, corresponding to flat directions of supersymmetry, lifted by supergravity corrections. The first stage corresponds to a period of either fast-roll or `locked' inflation, induced by an oscillating ... More
Is the Big Rip unreachable?Jul 02 2018Aug 27 2018I investigate the repercussions of particle production when the Universe is dominated by a hypothetical phantom substance. I show that backreaction due to particle production prevents the density from shooting to infinity at a Big Rip, but instead forces ... More
Correlated curvature perturbations and magnetogenesis from the GUT gauge bosonsJun 28 2008Jan 17 2013In the context of hybrid inflation at the scale of grand unification, it is shown that, if (some of) the gauge bosons of the unbroken grand unified group obtain a flat superhorizon spectrum of perturbations from inflation they can affect or even generate ... More
Synthesis of Strategies Using the Hoare Logic of Angelic and Demonic NondeterminismJun 29 2016Sep 02 2016We study a propositional variant of Hoare logic that can be used for reasoning about programs that exhibit both angelic and demonic nondeterminism. We work in an uninterpreted setting, where the meaning of the atomic actions is specified axiomatically ... More
Wiener Process with Reflection in Non-Smooth Narrow TubesApr 18 2010Wiener process with instantaneous reflection in narrow tubes of width {\epsilon}<<1 around axis x is considered in this paper. The tube is assumed to be (asymptotically) non-smooth in the following sense. Let $V^{\epsilon}(x)$ be the volume of the cross-section ... More
A Note On Degenerate Stochastic Integro-Differential EquationsJun 21 2014In the present article, solvability in Sobolev spaces is investigated for a class of degenerate stochastic integro-differential equations of parabolic type. Existence and uniqueness is obtained, and estimates are given for the solution.
Euler characteristics on virtually free productsNov 30 2015Jul 18 2016We define Euler characteristics on classes of residually finite and virtually torsion free groups and we show that they satisfy certain formulas in the case of amalgamated free products and HNN extensions over finite subgroups. These forumlas are obtained ... More
Quenched Large Deviations for Multiscale Diffusion Processes in Random EnvironmentsDec 05 2013Feb 23 2015We consider multiple time scales systems of stochastic differential equations with small noise in random environments. We prove a quenched large deviations principle with explicit characterization of the action functional. The random medium is assumed ... More
Spin on the latticeNov 13 2002Nov 26 2002I review the current status of hadronic structure computations on the lattice. I describe the basic lattice techniques and difficulties and present some of the latest lattice results; in particular recent results of the RBC group using domain wall fermions ... More
Footballonomics: The Anatomy of American Football; Evidence from 7 years of NFL game dataJan 17 2016Nov 21 2016Do NFL teams make rational decisions? What factors potentially affect the probability of wining a game in NFL? How can a team come back from a demoralizing interception? In this study we begin by examining the hypothesis of rational coaching, that is, ... More
Cops, Robber and Medianwidth ParametersMar 22 2016In previous work, we introduced median decompositions, a generalisation of tree decompositions where a graph can be modelled after any median graph, along with a hierarchy of $i$-medianwidth parameters $(mw_i)_{i\geq 1}$ starting from treewidth and converging ... More
CONSENSUS Project: Identifying publicly acceptable policy implementationsSep 25 2015Even though it is unrealistic to expect citizens to pinpoint the policy implementation that they prefer from the set of alternatives, it is still possible to infer such information through an exercise of ranking the importance of policy objectives according ... More
User-based key frame detection in social web videoApr 09 2012Video search results and suggested videos on web sites are represented with a video thumbnail, which is manually selected by the video up-loader among three randomly generated ones (e.g., YouTube). In contrast, we present a grounded user-based approach ... More
Non-degeneracy of the harmonic structure on Sierpinski GasketsMay 13 2016Jul 13 2016We prove that the harmonic extension matrices for the level-k Sierpinski Gasket are invertible for every k>2. This has been previously conjectured to be true by Hino in [6] and [7] and tested numerically for k<50.
Beyond the Dirac phase factorNov 16 2010We report on previously overlooked solutions of the usual gauge transformation equations that exhibit a new form of nonlocal quantal behavior with the well-known Relativistic Causality of classical fields affecting directly the phases of wavefunctions. ... More
Inflation at the TeV scale with a PNGB curvatonNov 28 2005We investigate a particular type of curvaton mechanism, under which inflation can occur at Hubble scale of order 1 TeV. The curvaton is a pseudo Nambu-Goldstone boson, whose order parameter increases after a phase transition during inflation, triggered ... More
Modelling Quintessential Inflation with BranesOct 16 2002Oct 17 2002I discuss why quintessential inflation model-building is more natural in the context of brane cosmology and study the dynamics of a particular model as an example.
The Curvaton Hypothesis and the eta-problem of Quintessential Inflation, with and without BranesDec 11 2002It is argued why, contrary to expectations, steep brane-inflation cannot really help in overcoming the eta-problem of quintessential inflation model-building. In contrast it is shown that the problem is substantially ameliorated under the curvaton hypothesis. ... More
Primordial Magnetic Fields from Superconducting Cosmic StringsJun 26 1997Cosmic strings are stable topological defects that may have been created at a phase transition in the early universe. It is a growing belief that, for a wide range of theoretical models, such strings may be superconducting and carry substantial currents ... More
All-loop correlators of integrable $λ$-deformed $σ$-modelsApr 27 2016May 31 2016We compute the 2- and 3-point functions of currents and primary fields of $\lambda$-deformed integrable $\sigma$-models characterized also by an integer $k$. Our results apply for any semisimple group $G$, for all values of the deformation parameter $\lambda$ ... More
$λ$-deformations of left-right asymmetric CFTsOct 17 2016We compute the all-loop anomalous dimensions of current and primary field operators in deformed current algebra theories based on a general semi-simple group, but with different (large) levels for the left and right sectors. These theories, unlike their ... More
Weyl anomaly and the $C$-function in $λ$-deformed CFTsOct 09 2018Dec 03 2018For a general $\lambda$-deformation of current algebra CFTs we compute the exact Weyl anomaly coefficient and the corresponding metric in the couplings space geometry. By incorporating the exact $\beta$-function found in previous works we show that the ... More
All-loop anomalous dimensions in integrable $λ$-deformed $σ$-modelsSep 09 2015Apr 28 2016We calculate the all-loop anomalous dimensions of current operators in $\lambda$-deformed $\sigma$-models. For the isotropic integrable deformation and for a semi-simple group $G$ we compute the anomalous dimensions using two different methods. In the ... More
An Open-Source OpenSim Oculomotor Model for Kinematics and Dynamics SimulationJul 19 2018Physics-based modeling and dynamic simulation of human eye movements has significant implications for improving our understanding of the oculomotor system and treating various visuomotor disorders. We introduce an open-source biomechanical model of the ... More
Generalised integrable $λ$- and $η$-deformations and their relationJun 18 2015Aug 31 2015We construct two-parameter families of integrable $\lambda$-deformations of two-dimensional field theories. These interpolate between a CFT (a WZW/gauged WZW model) and the non-Abelian T-dual of a principal chiral model on a group/symmetric coset space. ... More
Flux Superpotential in Heterotic M-theoryFeb 03 2006Jul 05 2006We derive the most general flux-induced superpotential for N=1 M-theory compactifications on seven-dimensional manifolds with SU(3) structure. Imposing the appropriate boundary conditions, this result applies for heterotic M-theory. It is crucial for ... More
Thickness-induced violation of de Haas-van Alphen effect through exact analytical solutions at a one-electron and a one-Composite Fermion levelMay 22 2013A systematic study of the energetics of electrons in an interface in a magnetic field is reported with exact analytical calculations based on a Landau Level (LL) picture, by serious consideration of the finite thickness of the Quantum Well (QW). The approach ... More
Accelerated hybrid steepest descent method for solving affinely constrained composite convex optimization tasksAug 08 2016Aug 19 2016The hybrid steepest descent method (HSDM) [Yamada,~'01] was introduced as a low-computational complexity tool for solving convex variational inequality problems over the fixed-point set of nonexpansive mappings in Hilbert spaces. Borrowing ideas from ... More
Optimal Resource Allocation for Uplink OFDMA in 802.11ax NetworksNov 02 2018Nov 05 2018In this paper, we study the scheduling and resource allocation problem for uplink OFDMA in IEEE 802.11ax WLANs. The OFDMA resource allocation problem for 802.11ax is inherently difficult to solve because consecutive subcarriers are grouped into resource ... More
The solutions of the 3rd and 4th Clay Millennium problemsFeb 19 2019In this treatise I present the solutions of the third Clay Millennium problem in the computational complexity and the fourth Clay Millennium problem in classical fluid dynamics.
Initial value problems for diffusion equations with singular potentialSep 28 2012Nov 16 2012Let $V$ be a nonnegative locally bounded function defined in $Q_\infty:=\BBR^n\times(0,\infty)$. We study under what conditions on $V$ and on a Radon measure $\gm$ in $\mathbb{R}^d$ does it exist a function which satisfies $\partial_t u-\xD u+ Vu=0$ in ... More
Topological restrictions on Anosov representationsApr 03 2019We characterize groups admitting Anosov representations into $\mathsf{SL}(3,\mathbb R)$, projective Anosov representations into $\mathsf{SL}(4,\mathbb R)$, and Borel Anosov representations into $\mathsf{SL}(4,\mathbb R)$. More generally, we obtain bounds ... More
An extension of the universal power series of SeleznevMay 25 2019We show generic existence of power series a with complex coefficients a_n, such that the sequence of partial sums of a new power series where its coefficients b_n are functions of a_0, a_1, ..., a_n approximate every polynomial uniformly on every compact ... More
Asymptotic behaviour of total generalised variationFeb 24 2015The recently introduced second order total generalised variation functional $\mathrm{TGV}_{\beta,\alpha}^{2}$ has been a successful regulariser for image processing purposes. Its definition involves two positive parameters $\alpha$ and $\beta$ whose values ... More
Towards automated neural design: An open source, distributed neural architecture research frameworkSep 20 2018NORD (Neural Operations Research & Development) is an open source distributed deep learning architectural research framework, based on PyTorch, MPI and Horovod. It aims to make research of deep architectures easier for experts of different domains, in ... More
Breaking the Interference Barrier in Dense Wireless Networks with Interference AlignmentOct 31 2017Dec 10 2017A fundamental problem arising in dense wireless networks is the high co-channel interference. Interference alignment (IA) was recently proposed as an effective way to combat interference in wireless networks. The concept of IA, though, is originated by ... More
Optimal Resource Allocation in IEEE 802.11ax Uplink OFDMA with Scheduled AccessNov 02 2018Jun 20 2019We consider the scheduling and resource allocation problem in AP-initiated uplink OFDMA transmissions of IEEE 802.11ax networks. The uplink OFDMA resource allocation problem is known to be non-convex and difficult to solve in general. However, due to ... More
Analysis of multiscale integrators for multiple attractors and irreversible Langevin samplersJun 30 2016Oct 09 2018We study multiscale integrator numerical schemes for a class of stiff stochastic differential equations (SDEs). We consider multiscale SDEs with potentially multiple attractors that behave as diffusions on graphs as the stiffness parameter goes to its ... More
Quasiconvexity at the boundary and the nucleation of austeniteAug 27 2014Mar 19 2015Motivated by experimental observations of H. Seiner et al., we study the nucleation of austenite in a single crystal of a CuAlNi shape-memory alloy stabilized as a single variant of martensite. In the experiments the nucleation process was induced by ... More
Recognition algorithms for binary signed-graphic matroidsNov 30 2010May 07 2012In this paper we provide two recognition algorithms for the class of signed-graphic matroids along with necessary and sufficient conditions for a matroid to be signed-graphic. Specifically, we provide a polynomial-time algorithm which determines whether ... More
3-Connected Cores In Random Planar GraphsJul 14 2009The study of the structural properties of large random planar graphs has become in recent years a field of intense research in computer science and discrete mathematics. Nowadays, a random planar graph is an important and challenging model for evaluating ... More
Dark energy as a remnant of inflation and electroweak symmetry breakingJul 11 2018Dec 04 2018It is shown that dark energy can be obtained from the interplay of the Higgs boson and the inflaton. A key element is the realization that electroweak symmetry breaking can trigger a second phase of rolling of the inflaton, which, when provided with the ... More
Topological restrictions on Anosov representationsApr 03 2019May 07 2019We characterize groups admitting Anosov representations into $\mathsf{SL}(3,\mathbb R)$, projective Anosov representations into $\mathsf{SL}(4,\mathbb R)$, and Borel Anosov representations into $\mathsf{SL}(4,\mathbb R)$. More generally, we obtain bounds ... More
On sequences of natural numbers having pairwise relatively prime termsJan 08 2015We prove some theorems which give sufficient conditions for the existence of prime numbers among the terms of a sequence which has pairwise relatively prime terms.
Topological genericity of nowhere differentiable functions in the disc and polydisc algebrasNov 05 2013In this paper we examine functions in the disc algebra $\mathcal{A}(D)$ and the polydisc algebra $\mathcal{A}(D^I)$, where $I$ is a finite or countably infinite set. We prove that, generically, for every $f \in \mathcal{A}(D)$ the continuous periodic ... More
Optimality of General Lattice Transformations with Applications to the Bain Strain in SteelOct 15 2015Jun 23 2016This article provides a rigorous proof of a conjecture by E.C. Bain in 1924 on the optimality of the so-called "Bain strain" based on a criterion of least atomic movement. A general framework that explores several such optimality criteria is introduced ... More
Resolvable Designs for Speeding up Distributed ComputingAug 14 2019Distributed computing frameworks such as MapReduce are often used to process large computational jobs. They operate by partitioning each job into smaller tasks executed on different servers. The servers also need to exchange intermediate values to complete ... More
DGM: A deep learning algorithm for solving partial differential equationsAug 24 2017Sep 05 2018High-dimensional PDEs have been a longstanding computational challenge. We propose to solve high-dimensional PDEs by approximating the solution with a deep neural network which is trained to satisfy the differential operator, initial condition, and boundary ... More
Agility Measurements Mismatch: A Validation Study on Three Agile Team Assessments in Software EngineeringApr 04 2019Many tools have been created for measuring the agility of software teams, thus creating a saturation in the field. Three agile measurement tools were selected in order to validate whether they yield sim-ilar results. The surveys of the tools were given ... More
A comparison principle for stochastic integro-differential equationsOct 22 2012Jan 03 2015A comparison principle for stochastic integro-differential equations driven by Levy processes is proved. This result is obtained via an extension of an Ito formula from [11] for the square of the norm of the positive part of $L_2-$valued, continuous semimartingales, ... More
Indifference pricing for Contingent Claims: Large Deviations EffectsOct 01 2014Feb 11 2016We study utility indifference prices and optimal purchasing quantities for a non-traded contingent claim in an incomplete semi-martingale market with vanishing hedging errors. We make connections with the theory of large deviations. We concentrate on ... More