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Diverging fluctuations of the Lyapunov exponentsJun 24 2016We show that in generic one-dimensional Hamiltonian lattices the diffusion coefficient of the maximum Lyapunov exponent diverges in the thermodynamic limit. We trace this back to the long-range correlations associated with the evolution of the hydrodynamic ... More

Road Detection by One-Class Color Classification: Dataset and ExperimentsDec 11 2014Dec 18 2014Detecting traversable road areas ahead a moving vehicle is a key process for modern autonomous driving systems. A common approach to road detection consists of exploiting color features to classify pixels as road or background. These algorithms reduce ... More

Node-Adapt, Path-Adapt and Tree-Adapt:Model-Transfer Domain Adaptation for Random ForestNov 09 2016Random Forest (RF) is a successful paradigm for learning classifiers due to its ability to learn from large feature spaces and seamlessly integrate multi-class classification, as well as the achieved accuracy and processing efficiency. However, as many ... More

The Parametrized Post-Newtonian-Vainshteinian FormalismJan 08 2015Jun 26 2015Light degrees of freedom that modify gravity on cosmological scales must be "screened" on solar system scales in order to be compatible with data. The Vainshtein mechanism achieves this through a breakdown of classical perturbation theory, as large interactions ... More

Jointly Optimal Sensing and Resource Allocation for Multiuser Overlay Cognitive RadiosNov 05 2012Successful deployment of cognitive radios requires efficient sensing of the spectrum and dynamic adaptation of the available resources according to the sensed (imperfect) information. While most works design these two tasks separately, in this paper we ... More

Hierarchical Adaptive Structural SVM for Domain AdaptationAug 22 2014A key topic in classification is the accuracy loss produced when the data distribution in the training (source) domain differs from that in the testing (target) domain. This is being recognized as a very relevant problem for many computer vision tasks ... More

Electromagnetics close beyond the critical state: thermodynamic prospectApr 12 2012Jul 27 2012A theory for the electromagnetic response of type-II superconductors close beyond the critical state is presented. Our formulation relies on general physical principles applied to the superconductor as a thermodynamic system. Equilibrium critical states, ... More

Pion scattering and the skyrmion in ChPT with many pionsJan 10 1994The large N effective action of the non-linear sigma model based in the coset O(N+1)/O(N) is obtained. The renormalization of this effective action requires the introduction of an infinite set of counterterms. However, there exit particular cases where, ... More

Strings on Eight-OrbifoldsMay 17 2004Jun 01 2004We present several examples of T^8/P orbifolds with $P \subset SU(4)$. We compute their Hodge numbers and consider turning on discrete torsion. We then study supersymmetric compactifications of type II, heterotic, and type I strings on these orbifolds. ... More

Complete non-orientable minimal surfaces in $\mathbb{R}^3$ and asymptotic behaviorDec 02 2013Jul 16 2014In this paper we give new existence results for complete non-orientable minimal surfaces in $\mathbb{R}^3$ with prescribed topology and asymptotic behavior.

Complete bounded embedded complex curves in C^2May 09 2013Jun 07 2016We prove that any convex domain of C^2 carries properly embedded complete complex curves. In particular, we exhibit the first examples of complete bounded embedded complex curves in C^2

Compact complete null curves in Complex 3-spaceJun 03 2011Jun 27 2011We prove that for any open orientable surface $S$ of finite topology, there exist a Riemann surface $\mathcal{M},$ a relatively compact domain $M\subset\mathcal{M}$ and a continuous map $X:\bar{M}\to\mathbb{C}^3$ such that: $\mathcal{M}$ and $M$ are homeomorphic ... More

Null Curves in $\mathbb{C}^3$ and Calabi-Yau ConjecturesDec 15 2009Jan 20 2012For any open orientable surface $M$ and convex domain $\Omega\subset \mathbb{C}^3,$ there exists a Riemann surface $N$ homeomorphic to $M$ and a complete proper null curve $F:N\to\Omega.$ This result follows from a general existence theorem with many ... More

Proper holomorphic embeddings of Riemann surfaces with arbitrary topology into $\mathbb{C}^2$Apr 11 2011We prove that given an open Riemann surface $N,$ there exists an open domain $M\subset N$ homeomorphic to $N$ which properly holomorphically embeds in $\mathbb{C}^2.$ Furthermore, $M$ can be chosen with hyperbolic conformal type. In particular, any open ... More

Properness of associated minimal surfacesMar 04 2012We prove that for any open Riemann surface $N$ and finite subset $Z\subset \mathbb{S}^1=\{z\in\mathbb{C}\,|\;|z|=1\},$ there exist an infinite closed set $Z_N \subset \mathbb{S}^1$ containing $Z$ and a null holomorphic curve $F=(F_j)_{j=1,2,3}:N\to\mathbb{C}^3$ ... More

A class of non-supersymmetric orientifoldsJun 09 2006We study type IIB orientifolds on T^{2d}/Z_N with supersymmetry broken by the compactification. We determine tadpole cancellation conditions including anti-branes and considering different actions for the parity Omega. Using these conditions we then obtain ... More

Crossing the cosmological constant line in a dilatonic brane-world model with and without curvature correctionsJul 29 2008We construct a new brane-world model composed of a bulk -with a dilatonic field-, plus a brane -with brane tension coupled to the dilaton-, cold dark matter and an induced gravity term. It is possible to show that depending on the nature of the coupling ... More

Approximation theory for non-orientable minimal surfaces and applicationsJul 09 2013We prove a version of the classical Runge and Mergelyan uniform approximation theorems for non-orientable minimal surfaces in Euclidean 3-space R3. Then, we obtain some geometric applications. Among them, we emphasize the following ones: 1. A Gunning-Narasimhan ... More

On harmonic quasiconformal immersions of surfaces in $\mathbb{R}^3$Feb 21 2011Jul 01 2011This paper is devoted to the study of the global properties of harmonically immersed Riemann surfaces in $\mathbb{R}^3.$ We focus on the geometry of complete harmonic immersions with quasiconformal Gauss map, and in particular, of those with finite total ... More

Minimal surfaces in $\mathbb{R}^3$ properly projecting into $\mathbb{R}^2$Oct 21 2009Jan 12 2012For all open Riemann surface M and real number $\theta \in (0,\pi/4),$ we construct a conformal minimal immersion $X=(X_1,X_2,X_3):M \to \mathbb{R}^3$ such that $X_3+\tan(\theta) |X_1|:M \to \mathbb{R}$ is positive and proper. Furthermore, $X$ can be ... More

Rotate your Networks: Better Weight Consolidation and Less Catastrophic ForgettingFeb 08 2018Dec 12 2018In this paper we propose an approach to avoiding catastrophic forgetting in sequential task learning scenarios. Our technique is based on a network reparameterization that approximately diagonalizes the Fisher Information Matrix of the network parameters. ... More

Two-Timescale Stochastic Dispatch of Smart Distribution GridsAug 17 2016Smart distribution grids should efficiently integrate stochastic renewable resources while effecting voltage regulation. The design of energy management schemes is challenging, one of the reasons being that energy management is a multistage problem where ... More

Rotate your Networks: Better Weight Consolidation and Less Catastrophic ForgettingFeb 08 2018In this paper we propose an approach to avoiding catastrophic forgetting in sequential task learning scenarios. Our technique is based on a network reparameterization that approximately diagonalizes the Fisher Information Matrix of the network parameters. ... More

Joint Coarse-And-Fine Reasoning for Deep Optical FlowAug 22 2018We propose a novel representation for dense pixel-wise estimation tasks using CNNs that boosts accuracy and reduces training time, by explicitly exploiting joint coarse-and-fine reasoning. The coarse reasoning is performed over a discrete classification ... More

Metric Learning for Novelty and Anomaly DetectionAug 16 2018When neural networks process images which do not resemble the distribution seen during training, so called out-of-distribution images, they often make wrong predictions, and do so too confidently. The capability to detect out-of-distribution images is ... More

Monocular Depth Estimation by Learning from Heterogeneous DatasetsMar 21 2018Sep 12 2018Depth estimation provides essential information to perform autonomous driving and driver assistance. Especially, Monocular Depth Estimation is interesting from a practical point of view, since using a single camera is cheaper than many other options and ... More

Blue-enhanced Supercontinuum Generation in a Fluorine-doped Graded-index Multimode FiberOct 27 2018Blue-enhanced, broadband supercontinuum generation in a 50 um core fluorine-doped graded-index multimode fiber is demonstrated by pumping with a 1064 nm picosecond source. Multi-octave supercontinuum spectrum extending from ~400 nm to 2,400 nm is achieved ... More

The dose-dense principle in chemotherapyMar 16 2017Jun 23 2017Chemotherapy is a class of cancer treatment that uses drugs to kill cancer cells. A typical chemotherapeutic protocol consists of several drugs delivered in cycles of three weeks. We present mathematical analyses demonstrating the existence of a maximum ... More

Proposed experiment for the quantum "Guess my number" protocolSep 27 2004Feb 10 2005An experimental realization of the entanglement-assisted "Guess my number" protocol for the reduction of communication complexity, introduced by Steane and van Dam, would require producing and detecting three-qubit GHZ states with an efficiency eta > ... More

Public Key Protocols over the Ring E_p(m)Jun 17 2016In this paper we use the nonrepresentable ring E_p(m)to introduce public key cryptosystems in noncommutative settings and based on the Semigrouop Action Problem and the Decomposition Problem respectively.

New complex analytic methods in the study of non-orientable minimal surfaces in $\mathbb{R}^n$Mar 05 2016The aim of this work is to adapt the complex analytic methods originating in modern Oka theory to the study of non-orientable conformal minimal surfaces in $\mathbb{R}^n$ for any $n\ge 3$. These methods, which we develop essentially from the first principles, ... More

Harmonic mappings and conformal minimal immersions of Riemann surfaces into $\mathbb{R}^n$Jul 19 2010Jul 22 2010We prove that for any open Riemann surface $N,$ natural number $n\geq 3,$ non-constant harmonic map $h:N\to \mathbb{R}^{n-2}$ and holomorphic 2-form $H$ on $N,$ there exists a weakly complete harmonic map $X=(X_j)_{j=1,\ldots,n}:N \to \mathbb{R}^n$ with ... More

Holomorphic Legendrian curvesJul 03 2016In this paper we study holomorphic Legendrian curves in the standard holomorphic contact structure on $\mathbb{C}^{2n+1}$ for any $n\in\mathbb{N}$. We provide several approximation and desingularization results which enable us to prove general existence ... More

A construction of complete complex hypersurfaces in the ball with control on the topologySep 08 2015Aug 30 2016Given a closed complex hypersurface $Z\subset \mathbb{C}^{N+1}$ $(N\in\mathbb{N})$ and a compact subset $K\subset Z$, we prove the existence of a pseudoconvex Runge domain $D$ in $Z$ such that $K\subset D$ and there is a complete proper holomorphic embedding ... More

Newtonian, Post Newtonian and Parameterized Post Newtonian limits of f(R, G) gravityNov 01 2013We discuss in detail the weak field limit of f(R,G) gravity taking into account analytic functions of the Ricci scalar R and the Gauss-Bonnet invariant G. Specifically, we develop, in metric formalism, the Newtonian, Post Newtonian and Parameterized Post ... More

Every meromorphic function is the Gauss map of a conformal minimal surfaceApr 02 2016Let $M$ be an open Riemann surface. We prove that every meromorphic function on $M$ is the complex Gauss map of a conformal minimal immersion $M\to\mathbb{R}^3$ which may furthermore be chosen as the real part of a holomorphic null curve $M\to\mathbb{C}^3$. ... More

Complete minimal surfaces and harmonic functionsOct 22 2009We prove that for any open Riemann surface $M$ and any non constant harmonic function $h:M \to \mathbb{R},$ there exists a complete conformal minimal immersion $X:M \to \mathbb{R}^3$ whose third coordinate function coincides with $h.$ As a consequence, ... More

Fast Isomorphism Testing of Graphs with Regularly-Connected ComponentsJun 22 2011The Graph Isomorphism problem has both theoretical and practical interest. In this paper we present an algorithm, called conauto-1.2, that efficiently tests whether two graphs are isomorphic, and finds an isomorphism if they are. This algorithm is an ... More

Embedded minimal surfaces in $\mathbb{R}^n$Sep 24 2014Dec 15 2015In this paper, we prove that every confomal minimal immersion of an open Riemann surface into $\mathbb{R}^n$ for $n\ge 5$ can be approximated uniformly on compacts by conformal minimal embeddings. Furthermore, we show that every open Riemann surface carries ... More

Minimal surfaces in minimally convex domainsOct 14 2015In this paper, we prove that every conformal minimal immersion of a compact bordered Riemann surface $M$ into a minimally convex domain $D\subset \mathbb{R}^3$ can be approximated, uniformly on compacts in $\mathring M=M\setminus bM$, by proper complete ... More

An Active Attack on a Multiparty Key Exchange ProtocolSep 03 2015The multiparty key exchange introduced in Steiner et al.\@ and presented in more general form by the authors is known to be secure against passive attacks. In this paper, an active attack is presented assuming malicious control of the communications of ... More

Tollan-Xicocotitlan: A reconstructed City by augmented realityJun 19 2014This project presents the analysis, design, implementation and results of Reconstruction Xicocotitlan Tollan-through augmented reality, which will release information about the Toltec culture supplemented by presenting an overview of the main premises ... More

Group key management based on semigroup actionsSep 03 2015Jul 28 2016In this work we provide a suite of protocols for group key management based on general semigroup actions. Construction of the key is made in a distributed and collaborative way. Examples are provided that may in some cases enhance the security level and ... More

Temporal Griffiths PhasesMay 18 2011Disorder is an unavoidable ingredient of real systems. Spatial disorder generates Griffiths phases (GPs) which, in analogy to critical points, are characterized by a slow relaxation of the order parameter and divergences of quantities such as the susceptibility. ... More

Minimal surfaces in minimally convex domainsOct 14 2015Jun 09 2018In this paper, we prove that every conformal minimal immersion of a compact bordered Riemann surface $M$ into a minimally convex domain $D\subset \mathbb{R}^3$ can be approximated, uniformly on compacts in $\mathring M=M\setminus bM$, by proper complete ... More

A static axisymmetric exact solution of $f(R)$-gravityNov 10 2012Dec 06 2012We present an exact, axially symmetric, static, vacuum solution for $f(R)$ gravity in Weyl's canonical coordinates. We obtain a general explicit expression for the dependence of $df(R)/dR$ upon the $r$ and $z$ coordinates and then the corresponding explicit ... More

Performance of Random Walks in One-Hop Replication NetworksAug 05 2009Random walks are gaining much attention from the networks research community. They are the basis of many proposals aimed to solve a variety of network-related problems such as resource location, network construction, nodes sampling, etc. This interest ... More

Evidence of accretion triggered oscillations in the pre-main-sequence interacting binary AK ScoOct 11 2012Pre-main sequence (PMS) binaries are surrounded by circumbinary disks from which matter falls onto both components. The material dragged from the circumbinary disk flows onto each star through independent streams channelled by the variable gravitational ... More

Interpolation and optimal hitting for complete minimal surfaces with finite total curvatureDec 13 2017Dec 10 2018We prove that, given a compact Riemann surface $\Sigma$ and disjoint finite sets $\varnothing\neq E\subset\Sigma$ and $\Lambda\subset\Sigma$, every map $\Lambda \to \mathbb{R}^3$ extends to a complete conformal minimal immersion $\Sigma\setminus E\to ... More

Every bordered Riemann surface is a complete conformal minimal surface bounded by Jordan curvesMar 02 2015Aug 19 2015In this paper we find approximate solutions of certain Riemann-Hilbert boundary value problems for minimal surfaces in $\mathbb{R}^n$ and null holomorphic curves in $\mathbb{C}^n$ for any $n\ge 3$. With this tool in hand we construct complete conformally ... More

Dyna-H: a heuristic planning reinforcement learning algorithm applied to role-playing-game strategy decision systemsJan 20 2011Jul 30 2011In a Role-Playing Game, finding optimal trajectories is one of the most important tasks. In fact, the strategy decision system becomes a key component of a game engine. Determining the way in which decisions are taken (online, batch or simulated) and ... More

Ion $H_2^+$ can dissociate in a strong magnetic fieldOct 04 2000Oct 18 2000In framework of a variational method the molecular ion $H_2^+$ in a magnetic field is studied. An optimal form of the vector potential corresponding to a given magnetic field (gauge fixing) is chosen variationally. It is shown that for any magnetic field ... More

An Application of Group Theory in Confidential Network CommunicationsOct 28 2016A new proposal for group key exchange is introduced which proves to be both efficient and secure and compares favorably with state of the art protocols.

CARLA: An Open Urban Driving SimulatorNov 10 2017We introduce CARLA, an open-source simulator for autonomous driving research. CARLA has been developed from the ground up to support development, training, and validation of autonomous urban driving systems. In addition to open-source code and protocols, ... More

First step towards a Devil's Staircase in Spin Crossover materials First step towards Devil's Staircase in Spin Crossover materialsMay 27 2016The devil is in the detail: Periodic and aperiodic spin-state concentration waves form during "Devil's staircase"-type spincrossover in a new bimetallic 2D coordination polymer {Fe[(Hg(SCN)3)2](4,4'-bipy)2}n.The unprecedented bimetallic 2D coordination ... More

Kinetic power of quasars and statistical excess of MOJAVE superluminal motionsJun 26 2012Jul 25 2012The MOJAVE survey contains 101 quasars with a total of 354 observed radio components that are different from the radio cores, among which 95% move with apparent projected superluminal velocities with respect to the core, and 45% have projected velocities ... More

Managing key multicasting through orthogonal systemsJul 04 2011Jan 01 2015In this paper we propose a new protocol to manage multicast key distribution. The protocol is based on the use of orthogonal systems in vector spaces. The main advantage in comparison to other existing multicast key management protocols is that the length ... More

Scalable Oriented-Service Architecture for Heterogeneous and Ubiquitous IoT DomainsNov 18 2013Internet of Things (IoT) grows quickly, and 50 billion of IoT devices will be interconnected by 2020. For the huge number of IoT devices, a high scalable discovery architecture is required to provide autonomous registration and look-up of IoT resources ... More

Dynamical evolution of two associated galactic barsSep 05 2014We study the dynamical interactions of mass systems in equilibrium under their own gravity that mutually exert and experience gravitational forces. The method we employ is to model the dynamical evolution of two isolated bars, hosted within the same galactic ... More

Anomalous Scaling of Fracture SurfacesFeb 25 1998We argue that fracture surfaces may exhibit anomalous dynamic scaling properties akin to what occurs in some models of kinetic roughening. We determine the complete scaling behavior of the local fluctuations of a brittle fracture in a granite block from ... More

Analytical solution of the radiative transfer equation for polarized lightSep 14 1999A new formalism is introduced for the transfer of polarized radiation. Stokes parameters are shown to be four-vectors in a Minkowski-like space and, most strikingly, the radiative transfer equation (RTE) turns out to be an infinitesimal transformation ... More

Cyclic Lorentzian Lie GroupsApr 29 2015We consider Lie groups equipped with a left-invariant cyclic Lorentzian metric. As in the Riemannian case, in terms of homogeneous structures, such metrics can be considered as different as possible from bi-invariant metrics. We show that several results ... More

Modular magnetic field on the z-direction on a chain of nuclear spin system and quantum Not and Controlled-Not gatesMar 02 2012We study the simulation of a single qubit rotation and Controlled-Not gate in a solid state one-dimensional chain of nuclear spins system interacting weakly through an Ising type of interaction with a modular component of the magnetic field in the z-direction, ... More

Boundary-layer turbulence in experiments of quasi-Keplerian flowsAug 19 2016Feb 23 2017Most flows in nature and engineering are turbulent because of their large velocities and spatial scales. Laboratory experiments of rotating quasi-Keplerian flows, for which the angular velocity decreases radially but the angular momentum increases, are ... More

About the Constant of Motion, Lagrangian and Hamiltonian of the Gravitational Attraction of Two Bodies with Variable Mass (Gylden-Meshcherskii problem)Mar 06 2007The Lagrangian, the Hamiltonian and the constant of motion of the gravitational attraction of two bodies when one of them has variable mass is considered. This is done by choosing the reference system in one of the bodies which allows to reduce the system ... More

Integration of the radiative transfer equation for polarized light: The exponential solutionNov 10 1998The radiative transfer equation (RTE) for polarized light accepts a convenient exponential solution when the absorption matrix commutes with its integral. We characterize some of the matrix depth variations which are compatible with the commutation condition. ... More

Reduction of Homogeneous Riemannian StructuresOct 28 2011The goal of this article is the study of homogeneous Riemannian structure tensors within the framework of reduction under a group $H$ of isometries. In a first result, $H$ is a normal subgroup of the group of symmetries associated to the reducing tensor ... More

Boundary-layer turbulence in experiments of quasi-Keplerian flowsAug 19 2016Most flows in nature and engineering are turbulent because of their large velocities and spatial scales. Laboratory experiments of rotating quasi-Keplerian flows, for which the angular velocity decreases radially but the angular momentum increases, are ... More

Comments on conformal stability of brane-world modelsJul 26 2001Sep 24 2001The stability of 5-D brane-world models under conformal perturbations is investigated. The analysis is carried out in the general case and then it is applied to particular solutions. It is shown that models with the Poincare and the de Sitter branes are ... More

GU Boo: A New 0.6 Msun Detached Eclipsing BinaryApr 29 2005We have found a new low-mass, double-lined, detached eclipsing binary, GU Boo, among a sample of new variables from the ROTSE-I database. The binary has an orbital period of 0.488728 +/- 0.000002 days, and estimated apparent magnitudes Vrotse = 13.7 and ... More

Orthogonal forms and orthogonality preservers on real function algebras revisitedNov 26 2015In 2014, we determine the precise form of a continuous orthogonal form on a commutative real C$^*$-algebra. We also describe the general form of a (not-necessarily continuous) orthogonality preserving linear map between commutative unital real C$^*$-algebras. ... More

Models for nuclear reactions with weakly bound systemsJul 11 2018Feb 04 2019In this contribution, I present a short overview of the theory of direct nuclear reactions, with special emphasis on the case of reactions induced by weakly-bound nuclei. After introducing some general results of quantum scattering theory, I present specific ... More

The $λ$-function in the space of trace class operatorsApr 04 2018Apr 09 2018Let $C_1(H)$ denote the space of all trace class operators on an arbitrary complex Hilbert space $H$. We prove that $C_1(H)$ satisfies the $\lambda$-property, and we determine the form of the $\lambda$-function of Aron and Lohman on the closed unit ball ... More

A survey on Tingley's problem for operator algebrasJan 08 2018Jan 09 2018We survey the most recent results on extension of isometries between special subsets of the unit spheres of C$^*$-algebras, von Neumann algebras, trace class operators, preduals of von Neumann algebras, and $p$-Schatten-von Neumann spaces, with special ... More

Tying up baric algebrasJul 29 2011Given two baric algebras $(A_1,\omega_1)$ and $(A_2,\omega_2)$ we describe a way to define a new baric algebra structure over the vector space $A_1\oplus A_2$, which we shall denote $(A_1\bowtie A_2,\omega_1\bowtie\omega_2)$. We present some easy properties ... More

The $f$-belosOct 30 2012The \emph{arbelos} is the shape bounded by three mutually tangent semicircles with collinear diameters. Recently, Sondow introduced the parabolic analog, the \emph{parbelos} and proved several properties of the parbelos similar to properties of the arbelos. ... More

A three-body model for the analysis of quasi-free scattering reactions in inverse kinematicsSep 25 2015A new method to calculate cross sections for $(p,pn)$ and $(p,2p)$ reactions measured under inverse kinematics conditions is proposed. The method uses the prior form of the scattering transition amplitude, and replaces the exact three-body wave function ... More

A note on 2-local representations of C$^*$-algebrasDec 24 2013Jul 30 2014We survey the results on linear local and 2-local homomorphisms and zero products preserving operators between C$^*$-algebras, and we incorporate some new precise observations and results to prove that every bounded linear 2-local homomorphism between ... More

Characterizing projections among positive operators in the unit sphereApr 11 2018Let $E$ and $P$ be subsets of a Banach space $X$, and let us define the unit sphere around $E$ in $P$ as the set $$Sph(E;P) :=\left\{ x\in P : \|x-b\|=1 \hbox{ for all } b\in E \right\}.$$ Given a C$^*$-algebra $A$, and a subset $E\subset A,$ we shall ... More

A new look at the trailing zeroes on $N!$Jun 26 2009Let us denote by $Z_b(n)$ the number of trailing zeroes in the base $b$ expansion of $n!$. In this paper we study with some detail the behavior of the function $Z_b$. In particular, since $Z_b$ is non-decreasing, we will characterize the points where ... More

Homotopy Fibre Sequences Induced by 2-FunctorsSep 23 2009Mar 25 2010This paper contains some contributions to the study of the relationship between 2-categories and the homotopy types of their classifying spaces. Mainly, generalizations are given of both Quillen's Theorem B and Thomason's Homotopy Colimit Theorem to 2-functors. ... More

Structures and Stabilities of CaO and MgO Clusters and Cluster Ions: An alternative interpretation of the experimental mass spectraApr 19 2000Sep 12 2000The structures and relative stabilities of doubly-charged nonstoichiometric (CaO)$_n$Ca$^{2+}$ (n=1--29) cluster ions and of neutral stoichiometric (MgO)$_n$ and (CaO)$_n$ (n=3,6,9,12,15,18) clusters are studied through {\em ab initio} Perturbed Ion plus ... More

A note on equipartitionJul 29 2007Jul 15 2008The problem of the existence of an equi-partition of a curve in $\R^n$ has recently been raised in the context of computational geometry. The problem is to show that for a (continuous) curve $\Gamma : [0,1] \to \R^n$ and for any positive integer N, there ... More

The W center in self-implanted silicon is the self-interstitial cluster I_3Feb 27 2002We identify the W center in self-implanted crystalline Si with the three-membered self-interstitial cluster I_3 on the basis of first-principles density-functional-theory calculations matching all the known experimental signatures of the center (emission ... More

Structures and Stabilities of Doubly-charged (MgO)nMg2+ (n=1-29) Cluster IonsAug 26 1998Dec 10 1998Ab initio perturbed ion plus polarization calculations are reported for doubly-charged nonstoichiometric (MgO)nMg2+ (n=1-29) cluster ions. We consider a large number of isomers with full relaxations of the geometries, and add the correlation correction ... More

A High Quality/Low Computational Cost Technique for Block Matching Motion EstimationOct 25 2007Motion estimation is the most critical process in video coding systems. First of all, it has a definitive impact on the rate-distortion performance given by the video encoder. Secondly, it is the most computationally intensive process within the encoding ... More

Performance analysis of FSO communications under LOS blockageJul 31 2017We analyze the performance of a free-space optical (FSO) link affected by atmospheric turbulence and line-of-sight (LOS) blockage. For this purpose, the atmospheric turbulence induced fading is modeled by the M-distribution, which includes the Gamma-Gamma ... More

Storage of correlated patterns in a perceptronMay 22 1995We calculate the storage capacity of a perceptron for correlated gaussian patterns. We find that the storage capacity $\alpha_c$ can be less than 2 if similar patterns are mapped onto different outputs and vice versa. As long as the patterns are in general ... More

Two emission line objects with z>0.2 in the optical filament apparently connecting the Seyfert galaxy NGC 7603 to its companionMar 26 2002Mar 27 2002We present new spectroscopic observations of an old case of anomalous redshift--NGC 7603 and its companion. The redshifts of the two galaxies which are apparently connected by a luminous filament are z=0.029 and z=0.057 respectively. We show that in the ... More

On the dust content of galaxy clustersSep 03 2014Sep 04 2014We present a study to estimate the dust content in galaxy clusters by using one the most complete existing catalogues of galaxy clusters based on SDSS data and following two methods: the first one compares the colours of samples of galaxies in the background ... More

The value of the fine structure constant over cosmological timesFeb 25 2010The optical spectra of objects classified as QSOs in the SDSS DR6 are analyzed with the aim of determining the value of the fine structure constant in the past and then check for possible changes in the constant over cosmological timescales. The analysis ... More

The Nature of Ultra Luminous X-ray SourcesFeb 15 2005We present spectroscopic observations of six optical counterparts of intermediate luminosity X-ray sources (ULXs) around nearby galaxies. The spectra of the six objects show the presence of broad emission features. The identification of these allow us ... More

The field surrounding NGC 7603: cosmological or non-cosmological redshifts?Jan 09 2004We present new observations of the field surrounding the Seyfert galaxy NGC 7603, where four galaxies with different redshifts--NGC 7603 (z=0.029), NGC 7603B (z=0.057) and two fainter emission line galaxies (z=0.245 and z=0.394)--are apparently connected ... More

Dust in clusters: separating the contribution of galaxies and intracluster mediaDec 01 2016We have analized a sample of 327 clusters of galaxies spanning the range 0.06-0.70 in redshift. Strong constraints on their mean intracluster emission by dust have been obtained using maps and catalogs from the HERSCHEL HerMES project; within a radius ... More

First tentative detection of anisotropy in the QSO distribution around nearby edge-on spiral galaxiesSep 19 2006AIMS. To check whether the polar angle distribution of QSOs around nearby spiral galaxies is isotropic or not. METHODS. A statistical analysis of the polar angle distribution of large samples of QSOs from the SDSS survey and Monte Carlo simulations to ... More

On the non-evolution of the dependence of black hole masses on bolometric luminosities for QSOsDec 19 2011There are extremely luminous quasi stellar objects (QSOs) at high redshift which are absent at low redshift. The lower luminosities at low redshifts can be understood as the external manifestation of either a lower Eddington ratio or a lower mass. To ... More

Toward a Clean Sample of Ultra-Luminous X-ray SourcesFeb 24 2006CONTEXT. Observational follow-up programmes for the characterization of ultra-luminous X-ray sources (ULXs) require the construction of clean samples of such sources in which the contamination by foreground/background sources is minimum. AIMS. In this ... More

Research on candidates for non-cosmological redshiftsSep 21 2005Sep 26 2005(Abridged:) The paradox of apparent optical associations of galaxies with very different redshifts, the so-called anomalous redshift problem, is around 35 years old, but is still without a clear solution and is surprisingly ignored by most of the astronomical ... More

QSO + galaxy association and discrepant redshifts in NEQ3Jan 28 2004Spectroscopy and deep imaging of the group NEQ3 are presented. This system is formed by three compact objects with relative separations of ~2.6 and ~2.8 arcsec, and a lenticular galaxy at ~17 arcsec from the geometric centre of the group. A diffuse filament ... More