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
Heating by transverse waves in simulated coronal loopsJun 08 2017Jun 13 2017Recent numerical studies of oscillating flux tubes have established the significance of resonant absorption in the damping of propagating transverse oscillations in coronal loops. The nonlinear nature of the mechanism has been examined alongside the Kelvin-Helmholtz ... 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
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
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
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.
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
A new proof of Vantieghem's theoremOct 26 2014We present a new proof of a primality criterion first proved by Emmanuel Vantieghem.
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
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
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
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
Review of AdS/CFT Integrability, Chapter IV.2: Deformations, Orbifolds and Open BoundariesDec 17 2010Aug 29 2011We review the role of integrability in the planar spectral problem of four-dimensional superconformal gauge theories besides N=4 SYM. The cases considered include the Leigh-Strassler marginal deformations of N=4 SYM, quiver theories which arise as orbifolds ... 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
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
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.
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
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.
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
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
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
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
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
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
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
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
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
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
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
Young stellar structures in four nearby galaxiesApr 11 2016A cluster finding method was developed and applied in four Local Group Galaxies (SMC, M31, M33 and NGC 6822). The aim is to study the young stellar population of these galaxies by identifying stellar structures in small and large scales. Also our aim ... 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
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
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
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
A disjoint union theorem for treesJul 27 2014We prove an infinitary disjoint union theorem for level products of trees. To implement the proof we develop a Hales-Jewett type result for words indexed by a level product of trees.
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
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
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
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.
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
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
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
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
Density symmetries for a class of 2-D diffusions with applications to financeJun 19 2017Apr 10 2018We study densities of two-dimensional diffusion processes with one non-negative component. For such diffusions, the density may explode at the boundary, thus making a precise specification of the boundary condition in the corresponding forward Kolmogorov ... More
Asynchronous Rumor Spreading on Random GraphsAug 05 2016We perform a thorough study of various characteristics of the asynchronous push-pull protocol for spreading a rumor on Erd\H{o}s-R\'enyi random graphs $G_{n,p}$, for any $p>c\ln(n)/n$ with $c>1$. In particular, we provide a simple strategy for analyzing ... More
Subsets of Products of Finite Sets of Positive Upper DensityNov 16 2012In this note we prove that for every sequence $(m_q)_{q}$ of positive integers and for every real $0<\delta\leqslant1$ there is a sequence $(n_q)_{q}$ of positive integers such that for every sequence $(H_q)_{q}$ of finite sets such that $|H_q|=n_q$ for ... More
Multiscale integrators for stochastic differential equations and irreversible Langevin samplersJun 30 2016Jul 07 2016We study multiscale integrator numerical schemes for a class of stiff stochastic differential equations (SDEs). We consider multiscale SDEs that behave as diffusions on graphs as the stiffness parameter goes to its limit. Classical numerical discretization ... More
Boosting Nodes for Improving the Spread of InfluenceSep 12 2016Information diffusion in networks has received a lot of recent attention. Most previous work addresses the influence maximization problem of selecting an appropriate set of seed nodes to initiate the diffusion process so that the largest number of nodes ... More
Modelling Inflation with a Power-law Approach to the Inflationary PlateauJul 08 2016Sep 18 2016A new family of inflationary models is introduced and analysed. The behaviour of the parameters characterising the models suggest preferred values, which generate the most interesting testable predictions. Results are further improved if late reheating ... More
Measure boundary value problem for semilinear elliptic equations with critical Hardy potentialsOct 05 2014Let $\Omega\subset\BBR^N$ be a bounded $C^2$ domain and $\CL_\gk=-\Gd-\frac{\gk}{d^2}$ the Hardy operator where $d=\dist (.,\prt\Gw)$ and $0<\gk\leq\frac{1}{4}$. Let $\ga_{\pm}=1\pm\sqrt{1-4\gk}$ be the two Hardy exponents, $\gl_\gk$ the first eigenvalue ... More
Five-brane Instantons vs Flux-induced Gauging of IsometriesJun 28 2006Oct 31 2006In five-dimensional heterotic M-theory there is necessarily nonzero background flux, which leads to gauging of an isometry of the universal hypermultiplet moduli space. This isometry, however, is poised to be broken by M5-brane instanton effects. We show ... More
The adaptive projected subgradient method constrained by families of quasi-nonexpansive mappings and its application to online learningAug 31 2010Aug 05 2011Many online, i.e., time-adaptive, inverse problems in signal processing and machine learning fall under the wide umbrella of the asymptotic minimization of a sequence of non-negative, convex, and continuous functions. To incorporate a-priori knowledge ... More
The "forgotten" pseudomomenta and gauge changes in generalized Landau Level problems: spatially nonuniform magnetic and temporally varying electric fieldsAug 24 2016By perceiving gauge invariance as an analytical tool in order to get insight into the states of the "generalized Landau problem" (a charged quantum particle moving inside a magnetic, and possibly electric field), and motivated by an early article that ... More
Landau Level Physics in a Quantum Well: new singular features in magnetization and violations of de Haas - van Alphen periodicitiesJan 06 2011Analytical calculations based on a Landau Level (LL) picture are reported for an interface (with a finite-width Quantum Well (QW)) and for a fully three-dimensional charged quantum electronic system in an external magnetic field. They lead to a sequence ... More
Stochastic Gradient Descent in Continuous TimeNov 17 2016Nov 27 2016We consider stochastic gradient descent for continuous-time models. Traditional approaches for the statistical estimation of continuous-time models, such as batch optimization, can be impractical for large datasets where observations occur over a long ... More
Initial conditions for inflationOct 19 2016Nov 15 2016We present a proposal, which manages to overcome the initial conditions problem of inflation with a plateau. An earlier period of proto-inflation, beginning at Planck scale, accounts for the Universe expansion and arranges the required initial conditions ... More
Subgaussianity is hereditarily determinedFeb 14 2019Let $n$ be a positive integer, let $\boldsymbol{X}=(X_1,\dots,X_n)$ be a random vector in $\mathbb{R}^n$ with bounded entries, and let $(\theta_1,\dots,\theta_n)$ be a vector in $\mathbb{R}^n$. We show that the subgaussian behavior of the random variable ... More
Real-Time detection, classification and DOA estimation of Unmanned Aerial VehicleFeb 27 2019The present work deals with a new passive system for real-time detection, classification and direction of arrival estimator of Unmanned Aerial Vehicles (UAVs). The proposed system composed of a very low cost hardware components, comprises two different ... More
Resource Allocation in Uplink OFDMA for IEEE 802.11ax Networks via Lyapunov OptimizationNov 02 2018Feb 19 2019We consider the scheduling and resource allocation problem in AP-initiated uplink OFDMA transmissions of IEEE 802.11ax networks. Due to the peculiar subcarrier allocation model of IEEE 802.11ax, the OFDMA resource allocation problem is non-convex and ... More
Sequential Monte Carlo for fractional Stochastic Volatility ModelsAug 11 2015Feb 25 2017In this paper we consider a fractional stochastic volatility model, that is a model in which the volatility may exhibit a long-range dependent or a rough/antipersistent behavior. We propose a dynamic sequential Monte Carlo methodology that is applicable ... More
Mean Field Analysis of Deep Neural NetworksMar 11 2019We analyze multi-layer neural networks in the asymptotic regime of simultaneously (A) large network sizes and (B) large numbers of stochastic gradient descent training iterations. We rigorously establish the limiting behavior of the multilayer neural ... More
Satisfiability Thresholds for Regular Occupation ProblemsNov 02 2018Apr 27 2019In the last two decades the study of random instances of constraint satisfaction problems (CSPs) has flourished across several disciplines, including computer science, mathematics and physics. The diversity of the developed methods, on the rigorous and ... More
Initial conditions for inflationOct 19 2016Jul 19 2017Within the $\alpha$-attractors framework we investigate scalar potentials with the same pole as the one featured in the kinetic term. We show that, in field space, this leads to directions without a plateau. Using this, we present a proposal, which manages ... More
Marginal Deformations of Tree-Level N=4 SYM from Twistor String TheoryDec 23 2005The topological B-model with target the supertwistor space CP(3|4) is known to describe perturbative amplitudes of N=4 Super Yang-Mills theory. We review the extension of this correspondence to the superconformal gauge theories that arise as marginal ... More
Homomorphism reductions on Polish groupsOct 18 2016In an earlier paper, we introduced the following pre-order on the subgroups of a given Polish group: if $G$ is a Polish group and $H,L \subseteq G$ are subgroups, we say $H$ is {\em homomorphism reducible} to $L$ iff there is a continuous group homomorphism ... More
Universal subgroups of Polish groupsSep 16 2012Aug 07 2013Given a class C of subgroups of a topological group G, we say that a subgroup H in C is a universal C subgroup of G if every subgroup K in C is a continuous homomorphic preimage of H. Such subgroups may be regarded as complete members of C with respect ... More
Asymptotic Enumeration of Graph Classes with Many ComponentsJan 14 2018We consider graph classes $\mathcal G$ in which every graph has components in a class $\mathcal{C}$ of connected graphs. We provide a framework for the asymptotic study of $\lvert\mathcal{G}_{n,N}\rvert$, the number of graphs in $\mathcal{G}$ with $n$ ... More
Maximum likelihood estimation for small noise multiscale diffusionsJan 27 2013Feb 18 2015We study the problem of parameter estimation for stochastic differential equations with small noise and fast oscillating parameters. Depending on how fast the intensity of the noise goes to zero relative to the homogenization parameter, we consider three ... More
On the boundedness of solutions of SPDEsDec 13 2013Jan 03 2015In this paper estimates for the uniform norm of solutions of parabolic SPDEs are derived. The result is obtained through iteration techniques, motivated by the work of Moser in deterministic settings. As an application of the main result, solvability ... More
A Faster Pseudopolynomial Time Algorithm for Subset SumJul 08 2015Dec 12 2016Given a multiset $S$ of $n$ positive integers and a target integer $t$, the subset sum problem is to decide if there is a subset of $S$ that sums up to $t$. We present a new divide-and-conquer algorithm that computes all the realizable subset sums up ... More
Dimension Reduction in Statistical Estimation of Partially Observed Multiscale ProcessesJul 21 2016Nov 26 2017We consider partially observed multiscale diffusion models that are specified up to an unknown vector parameter. We establish for a very general class of test functions that the filter of the original model converges to a filter of reduced dimension. ... More
On the regularisation of the noise for the Euler-Maruyama scheme with irregular driftDec 11 2018The strong rate of convergence of the Euler-Maruyama scheme for nondegenerate SDEs with irregular drift coefficients is considered. In the case of $\alpha$-H\"older drift in recent literature the rate $\alpha/2$ was proved in many related situations. ... More