Results for "Fredy Osorio"

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On Topologically Controlled Model Reduction for Discrete-Time SystemsMay 10 2019In this document the author proves that several problems in data-driven numerical approximation of dynamical systems in $\mathbb{C}^n$, can be reduced to the computation of a family of constrained matrix representations of elements of the group algebra ... More
On Topologically Controlled Model Reduction for Discrete-Time SystemsMay 10 2019May 19 2019In this document the author proves that several problems in data-driven numerical approximation of dynamical systems in $\mathbb{C}^n$, can be reduced to the computation of a family of constrained matrix representations of elements of the group algebra ... More
On the Approximation of Contractive Semigroups of Operators in Discretizable Hilbert SpacesDec 22 2010The Computation of discrete Contractive semigroups becomes necessary when we deal with several types of evolution equations in Discretizable Hilbert spaces, in this work we study some properties of the discrete forms of the contractive semigroups induced ... More
On Cyclic Finite-State Approximation of Data-Driven SystemsJul 15 2019Jul 18 2019In this document, some novel theoretical and computational techniques for constrained approximation of data-driven systems, are presented. The motivation for the development of these techniques came from structure-preserving matrix approximation problems ... More
On Matrix Schrödinger Unitary Groups in Particular Representations of Finite Dimensional Quantum Dynamical SystemsFeb 22 2011Mar 09 2011In this paper we study some particular types of matrix Schr\"odinger semigroups of the form $\exp(-it\mathbb{H})$ where $\mathbb{H}\in M_N(\mathbf{C})$ is the Hamiltonian of a given quantum dynamical system modeled in the finite dimensional Hilbert space ... More
On the Approximation of Nonlinear Evolution Equations in Particular C*-Algebras of OperatorsDec 22 2010Dec 27 2010In this article we deal with the stability and convergence of numerical solutions of nonlinear evolution equations of the form $A(u(t))+f(u(t))=u'(t)$, the numerical analysis of solutions to this problems will be performed using some methods from particular ... More
On Topologically Controlled Model Reduction for Discrete-Time SystemsMay 10 2019Jun 12 2019In this document the author proves that several problems in data-driven numerical approximation of dynamical systems in $\mathbb{C}^n$, can be reduced to the computation of a family of constrained matrix representations of elements of the group algebra ... More
Versatile Hall magnetometer with variable sensitivity assembly for characterization of the magnetic properties of nanoparticlesMay 14 2019Jun 17 2019A Hall magnetometer with variable sensitivity is constructed to measure the magnetic properties of magnetic nanoparticles manufactured by different methods. This novel magnetometer can also be used to measure bulk materials and samples in liquids. The ... More
Dynamical Deformation of Toroidal Matrix VarietiesJun 24 2015Jan 12 2017In this document we study the local connectivity of the sets whose elements are $m$-tuples of pairwise commuting normal matrix contractions. Given $\varepsilon>0$, we prove that there is $\delta>0$ such that for any two $m$-tuples of pairwise commuting ... More
Family Dependence in SU(3)_C X SU(3)_L X U(1)_X modelsMay 04 2005Aug 06 2005Using experimental results at the Z-pole and atomic parity violation, we perform a chi-squared fit at 95% CL to obtain family-dependent bounds to Z_2 mass and Z-Z' mixing angle in the framework of SU(3)_C X SU(3)_L X U(1)_X models. The allowed regions ... More
Rational consumer decisions in a peak time rebate programFeb 22 2018A rational behavior of a consumer is analyzed when the user participates in a Peak Time Rebate (PTR) mechanism, which is a demand response (DR) incentive program based on a baseline. A multi-stage stochastic programming is proposed from the demand side ... More
A novel incentive-based demand response model for Cournot competition in electricity marketsFeb 22 2018This paper presents an analysis of competition between generators when incentive-based demand response is employed in an electricity market. Thermal and hydropower generation are considered in the model. A smooth inverse demand function is designed using ... More
Z-Z' mixing in SU(3)_C X SU(3)_L X U(1)_X models with beta arbitraryAug 06 2005We perform a chi ^{2} fit at 95% CL to obtain model-dependent bounds to Z-Z' mixing angle theta and Z_2-mass in the framework of SU(3)_C X SU(3)_L X U(1)_X models with beta arbitrary. Using experimental results at the Z-pole and atomic parity violation, ... More
Estimating Norms of CommutatorsJan 17 2013Dec 04 2013We find estimates on the norms commutators of the form [f(x), y] in terms of the norm of [x, y] assuming that x and y are contractions in a C*-algebra A, with x normal and with spectrum within the domain of f. In particular we discuss [x^2, y] and [x^(1/2), ... More
Dirac operator on a noncommutative Toeplitz torusFeb 16 2018We construct a 1+ summable regular even spectral triple for a noncommutative torus defined by a C*-subalgebra of the Toeplitz algebra.
Stochastic moving particle semi-implicit for inviscid fluid wave simulationSep 13 2013The present paper introduces stochastic velocity as improvement for moving particle semi-implicit (MPS) method. This improvement is to overcome energy loss caused by numerical dissipation in the basic MPS that brings about rapid decay of waves. Stochastic ... More
Models for Dust and Molecular Emission of High-Mass ProtostarsDec 14 2007We present the results of a detailed modeling aimed to reproduce the spectral energy distribution (SED) of dust and molecular line emission of massive protostars under the hypothesis that they form via an accretion process. We model the emission originated ... More
Transmittance quantities probability distributions of waves through disordered systemsApr 23 2001Waves propagate through disordered systems in a variety of regimes. There is a threshold of disorder beyond which waves become localized and transport becomes restricted. The intensity I of the wave transmitted through a system has a dependence on the ... More
Dry Friction Avalanches: Experiment and Robin Hood modelNov 01 2005This paper presents experimental evidence and theoretical models supporting that dry friction stick-slip is described by self-organized criticality. We use the data, obtained with a pin-on-disc tribometer set to measure lateral force to examine the variation ... More
Dynamical Deformation of Toroidal Matrix VarietiesJun 24 2015Nov 30 2015In this document we study some particular types of contractive one-parameter semigroups of linear transformations over matrix sets, that can be used to perform local dynamical deformations. These deformations take place on matrix representations of tensor ... More
Local Deformation of Matrix WordsAug 30 2016In this document we study some local deformation properties of matrix representations of the universal C$^*$-algebras denoted by $\mathbb{I}^{m}_\varepsilon[p_1,\ldots,p_m]$ and $\mathbb{S}^{m-1}_\varepsilon[p_1,\ldots,p_m]$, and that we call {\bf Semi-Soft ... More
Versatile Hall magnetometer with variable sensitivity assembly for characterization of the magnetic properties of nanoparticlesMay 14 2019A Hall magnetometer with variable sensitivity is constructed to measure the magnetic properties of magnetic nanoparticles manufactured by different methods. This novel magnetometer can also be used to measure bulk materials and samples in liquids. The ... More
PredictionJul 14 2010This chapter first presents a rather personal view of some different aspects of predictability, going in crescendo from simple linear systems to high-dimensional nonlinear systems with stochastic forcing, which exhibit emergent properties such as phase ... More
Updates in Answer Set Programming: An Approach Based on Basic Structural PropertiesSep 29 2006We have studied the update operator defined for update sequences by Eiter et al. without tautologies and we have observed that it satisfies an interesting property This property, which we call Weak Independence of Syntax (WIS), is similar to one of the ... More
The value and credits of n-authors publicationsMay 26 2018Jul 04 2018Collaboration among researchers is becoming increasingly common, which raises a large number of scientometrics questions for which there is not a clear and generally accepted answer. For instance, what value should be given to a two-author or three-author ... More
On the Relative Projective SpaceOct 20 2017Dec 03 2018Let $(\mathcal C,\otimes,\mathbb 1)$ be an abelian symmetric monoidal category satisfying certain exactness conditions. In this paper we define a presheaf $\mathbb P^{n}_{\mathcal C}$ on the category of commutative algebras in $\mathcal C$ and we prove ... More
Transitional random matrix theory nearest-neighbor spacing distributionsNov 17 2009This paper presents a study of the properties of a matrix model that was introduced to describe transitions between all Wigner surmises of Random Matrix theory. New results include closed-form exact analytical expressions for the transitional probability ... More
On Cyclic Finite-State Approximation of Data-Driven SystemsJul 15 2019In this document, some novel theoretical and computational techniques for constrained approximation of data-driven systems, are presented. The motivation for these techniques came from structure-preserving matrix approximation problems, that appear in ... More
Approximation of Schr{ö}dinger Unitary Groups of Operators by Particular Projection MethodsJan 17 2011Mar 28 2011In this paper we work with the approximation of unitary groups of operators of the form $e^{-itH}$ where $H\in\mathscr{L}(\mathcal{H})$ is the Hamiltonian of a given quantum dynamical system modeled in the discretizable Hilbert space $\mathcal{H}=\mathcal{H}(G)$, ... More
Connecting Commuting Normal MatricesAug 18 2017In this document we study the local path connectivity of sets of $m$-tuples of commuting normal matrices with some additional geometric constraints in their joint spectra. In particular, given $\varepsilon>0$ and any fixed but arbitrary $m$-tuple $\mathbf{X}\in ... More
A slow-to-start traffic model related to a M/M/1 queueMar 27 2007May 31 2007We consider a system of ordered cars moving in $\R$ from right to left. Each car is represented by a point in $\R$; two or more cars can occupy the same point but cannot overpass. Cars have two possible velocities: either 0 or 1. An unblocked car needs ... More
On Uniform Connectivity of Algebraic Matrix SetsFeb 05 2018In this document we study the uniform local path connectivity of sets of $m$-tuples of pairwise commuting normal matrices with some additional constraints. More specifically, given given $\varepsilon>0$, a fixed metric $\eth$ in ${M_n(\mathbb{C})}^m$ ... More
Mg line formation in late-type stellar atmospheres: II. Calculations in a grid of 1D modelsOct 17 2015Jan 29 2016Mg is the alpha element of choice for Galactic population and chemical evolution studies as it is easily detectable in all late-type stars. Such studies require precise elemental abundances, and thus departures from LTE need to be accounted for. Our goal ... More
Entanglement constant for conformal familiesJul 02 2015Sep 16 2015We show that in 1+1 dimensional conformal field theories, exciting a state with a local operator increases the Renyi entanglement entropies by a constant which is the same for every member of the conformal family. Hence, it is an intrinsic parameter that ... More
About the Cauchy problem in Stelle's quadratic gravityNov 19 2018Feb 22 2019The focus of the present work is on the Cauchy problem for the quadratic gravity models introduced in \cite{stelle}-\cite{stelle2}. These are renormalizable higher order derivative models of gravity, but at cost of ghostly states propagating in the phase ... More
Non-homogenous disks in the chain of matricesNov 16 2011We investigate the generating functions of multi-colored discrete disks with non-homogenous boundary conditions in the context of the Hermitian multi-matrix model where the matrices are coupled in an open chain. We show that the study of the spectral ... More
Range-based argumentation semantics as 2-valued modelsFeb 29 2016Characterizations of semi-stable and stage extensions in terms of 2-valued logical models are presented. To this end, the so-called GL-supported and GL-stage models are defined. These two classes of logical models are logic programming counterparts of ... More
Mass spectrum and decay constants of radially excited vector mesonsApr 27 2017We calculate the masses and weak decay constants of flavorless ground and radially excited $J^P=1^-$ mesons and the corresponding quantities for the K^*, within a Poincar\'e covariant continuum framework based on the Bethe-Salpeter equation. We use in ... More
Multivector variate distributions: An application in FinanceJun 24 2018A new family of multivariate distributions, which shall be termed multivector variate distributions, based in the family of the multivariate contoured elliptically distribution is proposed. Several particular cases of multivector variate distributions ... More
Entanglement and mutual information in two-dimensional nonrelativistic field theoriesOct 13 2015Feb 11 2016We carry out a systematic study of entanglement entropy in nonrelativistic conformal field theories via holographic techniques. After a discussion of recent results concerning Galilean conformal field theories, we deduce a novel expression for the entanglement ... More
Applications of Intuitionistic Logic in Answer Set ProgrammingMay 27 2003We present some applications of intermediate logics in the field of Answer Set Programming (ASP). A brief, but comprehensive introduction to the answer set semantics, intuitionistic and other intermediate logics is given. Some equivalence notions and ... More
Scrambling without chaos in RCFTFeb 21 2016Jul 19 2017In this paper we investigate measures of chaos and entanglement in rational conformal field theories in 1+1 dimensions. First, we derive a universal formula for the late time value of the out-of-time-ordered correlators for this class of theories. Our ... More
Free-kick condition for entanglement entropy in higher curvature gravityMay 04 2015Sep 03 2015In order to compute the entanglement entropy for a given region in a theory with an Einstein gravity dual, the Ryu-Takayanagi prescription tells us that we must compute the the area of an extremal surface anchored to the entangling region. However, if ... More
Sharp isoperimetric inequalities for small volumes in complete noncompact Riemannian manifolds of bounded geometry involving the scalar curvatureNov 05 2016Nov 11 2016We provide an isoperimetric comparison theorem for small volumes in an $n$-dimensional Riemannian manifold $(M^n,g)$ with strong bounded geometry, as in Definition $2.3$, involving the scalar curvature function. Namely in strong bounded geometry, if the ... More
Long-term K$_S$-band photometric monitoring of L dwarfsAug 01 2014(abridged) We perform photometric time-series analysis of a sample of ten early to mid-L dwarfs in the field over three years of $K_s$-band observations with the OMEGA 2000 infrared camera of the 3.5m telescope on Calar Alto Observatory between January ... More
Halogen Bonding Interactions: Revised Benchmarks and a New Assessment of Exchange vs. DispersionMar 06 2018We present a new analysis of exchange and dispersion effects for calculating halogen-bonding interactions in a wide variety of complex dimers (69 total) within the XB18 and XB51 benchmark sets. Contrary to previous work on these systems, we find that ... More
On the effective character of a non abelian DBI actionNov 20 2000Nov 29 2000We study the way Lorentz covariance can be reconstructed from Matrix Theory as a IMF description of M-theory. The problem is actually related to the interplay between a non abelian Dirac-Born-Infeld action and Super-Yang-Mills as its generalized non-relativistic ... More
Scrambling without chaos in RCFTFeb 21 2016Oct 31 2016In this letter we investigate measures of chaos and entanglement in rational conformal field theories in 1+1 dimensions. First, we derive a formula for the late time value of the out-of-time-order corre- lators for these class of theories. Our universal ... More
Probing the stability of the spin liquid phases in the Kitaev-Heisenberg model using tensor network algorithmsAug 18 2014Nov 27 2014We study the extent of the spin liquid phases in the Kitaev-Heisenberg model using infinite Projected Entangled-Pair States tensor network ansatz wave functions directly in the thermodynamic limit. To assess the accuracy of the ansatz wave functions we ... More
An Empirical Evaluation of Deep Learning for ICD-9 Code Assignment using MIMIC-III Clinical NotesFeb 07 2018Code assignment is important on many levels in the modern hospital, from ensuring accurate billing process to creating a valid record of patient care history. However, the coding process is tedious, subjective, and requires medical coders with extensive ... More
Infinite Matrix Product States vs Infinite Projected Entangled-Pair States on the Cylinder: a comparative studyMay 09 2017In spite of their intrinsic one-dimensional nature matrix product states have been systematically used to obtain remarkably accurate results for two-dimensional systems. Motivated by basic entropic arguments favoring projected entangled-pair states as ... More
Graph duality as an instrument of Gauge-String correspondenceMay 18 2015May 21 2016We explore an identity between two branching graphs and propose a physical meaning in the context of the gauge-gravity correspondence. From the mathematical point of view, the identity equates probabilities associated with $\mathbb{GT}$, the branching ... More
Hot Molecular Cores and the Formation of Massive StarsSep 28 1999It has been proposed that some hot molecular cores (HMCs) harbor a young embedded massive star, which heats an infalling envelope and accretes mass at a rate high enough to ``choke off'' an incipient HII region. This class of HMCs would mark the youngest ... More
On the generation of bipartite grids with controlled regularity for 2-D and 3-D simply connected domainsDec 25 2013We present a procedure to generate bipartite grids for simply connected domains in 2-D and 3-D of prescribed size and controlled regularity elements. The mesh elements $K$ of the triangulation satisfy $\zeta_{K} \leq C$ where $\zeta_{K}$ is the regularity ... More
Entanglement, anomalies and Mathisson's helicesJun 18 2018Jun 26 2018We study the physical properties of a length-torsion functional which encodes the holographic entanglement entropy for 1+1 dimensional theories with chiral anomalies. Previously, we have shown that its extremal curves correspond to the mysterious Mathisson's ... More
Sharp isoperimetric inequalities for small volumes in complete noncompact Riemannian manifolds of bounded geometry involving the scalar curvatureNov 05 2016We provide an isoperimetric comparison theorem for small volumes in an $n$-dimensional Riemannian manifold $(M^n,g)$ with strong bounded geometry, as in Definition $2.3$, involving the scalar curvature function. Namely in strong bounded geometry, if the ... More
An Empirical Evaluation of Deep Learning for ICD-9 Code Assignment using MIMIC-III Clinical NotesFeb 07 2018Jun 08 2019Background and Objective: Code assignment is of paramount importance in many levels in modern hospitals, from ensuring accurate billing process to creating a valid record of patient care history. However, the coding process is tedious and subjective, ... More
Corner-Impact Bifurcations: a novel class of discontinuity-induced bifurcations in Cam-Follower SystemsNov 07 2007This paper is concerned with the analysis of a class of impacting systems of relevance in applications: cam-follower systems. We show that these systems, which can be modelled as discontinuously forced impact oscillators, can exhibit complex behaviour ... More
Counting paths with Schur transitionsApr 22 2016In this work we explore the structure of the branching graph of the unitary group using Schur transitions. We find that these transitions suggest a new combinatorial expression for counting paths in the branching graph. This formula, which is valid for ... More
Gravitational anomalies, entanglement entropy, and flat-space holographyJul 23 2015Feb 29 2016We introduce a prescription to compute the entanglement entropy of Galilean conformal field theories by combining gravitational anomalies and an \.{I}n\"{o}n\"{u}-Wigner contraction. We find that our expression for the entanglement entropy in the thermal ... More
Towards a Probabilistic Definition of SeizuresNov 13 2011This writing: a) Draws attention to the intricacies inherent to the pursuit of a universal seizure definition even when powerful, well understood signal analysis methods are utilized to this end; b) Identifies this aim as a multi-objective optimization ... More
Automated Seizure Detection: Unrecognized Challenges, Unexpected InsightsNov 13 2011One of epileptology's fundamental aims is the formulation of a universal, internally consistent seizure definition. To assess this aim's feasibility, three signal analysis methods were applied to a seizure time series and performance comparisons were ... More
Spectroscopic estimate of surface gravity for a planetary member in the Sigma Ori clusterJul 13 2003We present intermediate-resolution (R=1500) near-infrared spectroscopy from 1.17 $\mu$m to 1.37 $\mu$m of the spectral type T planetary candidate member in the \sigori cluster S Ori 70 reported by Zapatero Osorio et al. (2002). The new data have been ... More
Heating up branes in gauged supergravityJun 11 2014Oct 08 2014In this note, we explore the solution space of non-extremal black objects in $4D$ and $5D$ ${\cal N}=2$ gauged supergravity in the presence of fluxes. We present first order rewritings of the $4D$ action for a classes of non-extremal dyonic and electric ... More
Entanglement and mutual information in two-dimensional nonrelativistic field theoriesOct 13 2015Sep 11 2017We carry out a systematic study of entanglement entropy in nonrelativistic conformal field theories via holographic techniques. After a discussion of recent results concerning Galilean conformal field theories, we deduce a novel expression for the entanglement ... More
Semantics for Possibilistic Disjunctive ProgramsJun 03 2011In this paper, a possibilistic disjunctive logic programming approach for modeling uncertain, incomplete and inconsistent information is defined. This approach introduces the use of possibilistic disjunctive clauses which are able to capture incomplete ... More
Ultrafast Magnetic Resonance ImagingSep 17 2018We propose a radical advance in Magnetic Resonance Imaging. MRI remains slow because it requires successive applications of magnetic field gradients to encode for spatial location. Parallel MRI accelerates imaging by permitting undersampling of k-space ... More
Spinning probes and helices in AdS$_3$Mar 14 2018We study extremal curves associated with a functional which is linear in the curve's torsion. The functional in question is known to capture the properties of entanglement entropy for two-dimensional conformal field theories with chiral anomalies and ... More
Scrambling without chaos in RCFTFeb 21 2016Feb 29 2016In this letter we investigate measures of chaos and entanglement scrambling in rational conformal field theories in 1+1 dimensions. First, we derive a formula for the late time value of the out-of-time-order correlators for these class of theories. Our ... More
On the Shape of Things: From holography to elasticaNov 10 2016We explore the question of which shape a manifold is compelled to take when immersed into another one, provided it must be the extremum of some functional. We consider a family of functionals which depend quadratically on the extrinsic curvatures and ... More
A CCD Imaging Search for Wide Metal-Poor BinariesFeb 12 2004We explored the regions within a radius of 25 arcsec around 473 nearby, low-metallicity G- to M-type stars using (VR)I optical filters and small-aperture telescopes. About 10% of the sample was searched up to angular separations of 90 arcsec. We applied ... More
Liquid Humans - Pedestrian Simulator based on the LWR-modelJan 22 2016Dense human flow has been a concern for the safety of public events for a long time. Macroscopic pedestrian models, which are mainly based on fluid dynamics, are often used to simulate huge crowds due to their low computational costs. Similar approaches ... More
Stochastic Electron Acceleration by the Whistler Instability in a Growing Magnetic FieldAug 24 2017Nov 22 2017We use 2D particle-in-cell (PIC) simulations to study the effect of the saturated whistler instability on the viscous heating and nonthermal acceleration of electrons in a shearing, collisionless plasma with a growing magnetic field, \textbf{B}. In this ... More
On the Shape of Things: From holography to elasticaNov 10 2016Sep 11 2017We explore the question of which shape a manifold is compelled to take when immersed in another one, provided it must be the extremum of some functional. We consider a family of functionals which depend quadratically on the extrinsic curvatures and on ... More
On the sigma-model of deformed special geometryDec 18 2012Feb 12 2014We discuss the deformed sigma-model that arises when considering four-dimensional N=2 abelian vector multiplets in the presence of an arbitrary chiral background field. In addition, we allow for a class of deformations of special geometry by non-holomorphic ... More
Preferred extensions as stable modelsMar 26 2008Given an argumentation framework AF, we introduce a mapping function that constructs a disjunctive logic program P, such that the preferred extensions of AF correspond to the stable models of P, after intersecting each stable model with the relevant atoms. ... More
SpatialPack: Computing the Association Between Two Spatial ProcessesNov 16 2016An R package SpatialPack that implements routines to compute point estimators and perform hypothesis testing of the spatial association between two stochastic sequences is introduced. These methods address the spatial association between two processes ... More
Local Matrix Homotopies and Soft ToriMay 21 2016Jun 22 2016We present solutions to local connectivity problems in matrix representations of the form $C([-1,1]^{N}) \to A_{n,\varepsilon} \leftarrow C_{\varepsilon}(\mathbb{T}^{2})$ for any $\varepsilon\in[0,2]$ and any integer $n\geq 1$, where $A_{n,\varepsilon}\subseteq ... More
Limiting gaming opportunities on incentive-based demand response programsFeb 23 2018Demand Response (DR) is a program designed to match supply and demand by modifying consumption profile. Some of these programs are based on economic incentives, in which, a user is paid to reduce his energy requirements according to an estimated baseline. ... More
String Variations on Kaluza-Klein CosmologyMay 25 1993May 26 1993We study the cosmological solutions of the two-dimensional Brans-Dicke equations considering a gas of $c=1$ strings in $S^{1}\times \mbox{\bf R}$ as the source of the gravitational field. We also study the implications of the $R$-duality invariance on ... More
Finite Temperature Matrix TheoryMar 06 1998Apr 28 1998We present the way the Lorentz invariant canonical partition function for Matrix Theory as a light-cone formulation of M-theory can be computed. We explicitly show how when the eleventh dimension is decompactified, the N = 1 eleven dimensional SUGRA partition ... More
Simultaneous optical and near-infrared linear spectropolarimetry of the earthshineJan 23 2014Aims: We aim to extend our current observational understanding of the integrated planet Earth spectropolarimetry from the optical to the near-infrared wavelengths. Major biomarkers like O$_{\rm 2}$ and water vapor are strong flux absorbents in the Earth ... More
Performance of local orbital basis sets in the self-consistent Sternheimer method for dielectric matrices of extended systemsFeb 01 2012We present a systematic study of the performance of numerical pseudo-atomic orbital basis sets in the calculation of dielectric matrices of extended systems using the self-consistent Sternheimer approach of [F. Giustino et al., Phys. Rev. B 81 (11), 115105 ... More
The influence of electron collisions on non-LTE Li line formation in stellar atmospheresFeb 08 2011Mar 21 2011The influence of the uncertainties in the rate coefficient data for electron-impact excitation and ionization on non-LTE Li line formation in cool stellar atmospheres is investigated. We examine the electron collision data used in previous non-LTE calculations ... More
Backaction in metasurface etalonsMay 11 2015Feb 19 2016We consider the response of etalons created by a combination of a conventional mirror and a metasurface, composed of a periodic lattice of metal scatterers with a resonant response. This geometry has been used previously for perfect absorption, in so-called ... More
Photometric Variability in the Ultracool Dwarf BRI 0021-0214: Possible Evidence for Dust CloudsApr 23 2001We report CCD photometric monitoring of the nonemission ultracool dwarf BRI 0021-0214 (M9.5) obtained during 10 nights in 1995 November and 4 nights in 1996 August, with CCD cameras at 1 m class telescopes on the observatories of the Canary Islands. We ... More
Correlations in orbital angular momentum of spatially entangled paired photons generated in parametric downconversionNov 28 2007What are the orbital angular momentum correlations between spatially entangled photon pairs generated in spontaneous parametric down-conversion? We show that the answer to this question can be given in two alternative, although complementary, ways. The ... More
On a switching control problem with càdlàg costsJul 08 2019This work addresses a switching control problem under which the cost associated with the changes of regimes is allowed to have discontinuities in time. Our main contribution is to show several characterizations of the optimal cost function as well as ... More
Scalar Field Dark Matter: behavior around black holesJul 30 2010Jun 17 2011We present the numerical evolution of a massive test scalar fields around a Schwarzschild space-time. We proceed by using hyperboloidal slices that approach future null infinity, which is the boundary of scalar fields, and also demand the slices to penetrate ... More
Evolution of a mass-less test scalar field on Boson Stars space-timesJul 07 2010Jul 30 2010We numerically solve the mass-less test scalar field equation on the space-time background of boson stars and black holes. In order to do so, we use a numerical domain that contains future null infinity. We achieve this construction using a scri-fixing ... More
CAFE: A New Relativistic MHD CodeAug 25 2014May 12 2015We introduce CAFE, a new independent code designed to solve the equations of Relativistic ideal Magnetohydrodynamics (RMHD) in 3D. We present the standard tests for a RMHD code and for the Relativistic Hydrodynamics (RHD) regime since we have not reported ... More
The String Density of States from The Convolution TheoremJan 23 1997We study the microcanonical density of states and the thermal properties of a bosonic string gas starting from a calculation of the Helmholtz free energy in the S-representation. By adding more and more strings to the single string system, we induce that, ... More
Variations on Kaluza-Klein CosmologyMay 25 1993May 26 1993We investigate the cosmological consequences of having quantum fields living in a space with compactified dimensions. We will show that the equation of state is not modified by topological effects and so the dynamics of the universe remains as it is in ... More
Strings below the Planck scaleJan 22 1992Jan 30 1992We show that, for a class of critical strings in ${\bf R}\times S^{1}$-target space, the description of string theory given by its field content (analog model) breaks down when the radius of $S^{1}$ decreases below $R_{0}=\sqrt{\alpha^{\prime}}$, the ... More
On the stability of the primordial closed string gasJul 08 2005Jan 13 2006We recast the study of a closed string gas in a toroidal container in the physical situation in which the single string density of states is independent of the volume because energy density is very high. This includes the gas for the well known Brandenberger-Vafa ... More
Thermodynamic nonextensivity in a closed string gasJun 04 2004Nov 29 2004Well known results in string thermodynamics show that there is always a negative specific heat phase in the microcanonical description of a gas of closed free strings whenever there are no winding modes present. We will carefully compute the number of ... More
A Cosmological Interpretation of DualityNov 15 1993Nov 19 1993We study the cosmological meaning of duality symmetry by considering a two dimensional model of string cosmology. We find that as seen by an internal observer in this universe, the scale factor rebounds at the self-dual length. This rebound is a consequence ... More
Lucky Imaging of M subdwarfsMar 24 2009The knowledge of the binary properties of metal-poor and solar-metallicity stars can shed light on the potential differences between the formation processes responsible for both types of objects. The aim of the project is to determine the binary properties ... More
Spectroscopy of New Substellar Candidates in the Pleiades: Towards a Spectral Sequence for Young Brown DwarfsApr 15 1996We present optical and near-IR spectroscopy (600--1000 nm) of 8 faint (I$>$18) very red (R--I$>$2.2) objects discovered in a deep CCD survey of the Pleiades (Zapatero-Osorio et al. 1996). We compare them with reliable cluster members like PPl 15 and Teide ... More
On the Interpretation of the Optical Spectra of L-type DwarfsJan 05 2000We present synthetic optical spectra in the range 640-930 nm of a sample of field L dwarfs and the brown dwarf GL229B. Our computations show that Li, Na, K, Rb, and Cs govern the spectra of these objects, with Na and K contributing significantly to block ... More