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Results for "Guillermo Suarez-Tangil"

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Eight Years of Rider Measurement in the Android Malware Ecosystem: Evolution and Lessons LearnedJan 24 2018Despite the growing threat posed by Android malware, the research community is still lacking a comprehensive view of common behaviors and trends exposed by malware families active on the platform. Without such view, the researchers incur the risk of developing ... More
A First Look at the Crypto-Mining Malware Ecosystem: A Decade of Unrestricted WealthJan 03 2019Illicit crypto-mining leverages resources stolen from victims to mine cryptocurrencies on behalf of criminals. While recent works have analyzed one side of this threat, i.e.: web-browser cryptojacking, only white papers and commercial reports have partially ... More
Smart Home Personal Assistants: A Security and Privacy ReviewMar 13 2019Mar 17 2019Smart Home Personal Assistants (SPA) are an emerging innovation that is changing the way in which home users interact with the technology. However, there are a number of elements that expose these systems to various risks: i) the open nature of the voice ... More
On the Origins of Memes by Means of Fringe Web CommunitiesMay 31 2018Sep 22 2018Internet memes are increasingly used to sway and manipulate public opinion. This prompts the need to study their propagation, evolution, and influence across the Web. In this paper, we detect and measure the propagation of memes across multiple Web communities, ... More
"You Know What to Do": Proactive Detection of YouTube Videos Targeted by Coordinated Hate AttacksMay 21 2018Over the years, the Web has shrunk the world, allowing individuals to share viewpoints with many more people than they are able to in real life. At the same time, however, it has also enabled anti-social and toxic behavior to occur at an unprecedented ... More
Smart Home Personal Assistants: A Security and Privacy ReviewMar 13 2019Smart Home Personal Assistants (SPA) are an emerging innovation that is changing the way in which home users interact with the technology. However, there are a number of elements that expose these systems to various risks: i) the open nature of the voice ... More
When the optimal is not the best: parameter estimation in complex biological modelsNov 18 2010Background: The vast computational resources that became available during the past decade enabled the development and simulation of increasingly complex mathematical models of cancer growth. These models typically involve many free parameters whose determination ... More
Why aren't quantum correlations maximally nonlocal? Biased local randomness as essential feature of quantum mechanicsFeb 14 2009It is argued that the quantum correlations are not maximally nonlocal to make it possible to control local outcomes from outside spacetime, and quantum mechanics emerges from timeless nonlocality and biased local randomness. This rules out a world described ... More
Bohm's "quantum potential" can be considered falsified by experimentOct 08 2014A Michelson-Morley-type experiment is described, which exploits two-photon interference between entangled photons instead of classical light interference. In this experimental context, the negative result (no shift in the detection rates) rules out David ... More
Decision at the beam-splitter, or decision at detection, that is the questionApr 26 2012Apr 15 2013I argue that nonlocal decision of the outcomes at detection excludes any alternative theory to quantum mechanics: Not all that matters for the results of physical experiments is content in space-time, but all that is in space-time is accessible to observation. ... More
Do Hardy-type proposals test nonlocality of single-particle?Apr 12 2012Apr 15 2013It is argued that Hardy-type proposals assume either nonlocality at detection, and then beg the question, or "local empty waves" (local hidden variables), and then have to accept "many worlds" and cannot prove nonlocality.
Covariant vs. non-covariant quantum collapse: Proposal for an experimental testNov 29 2013Jan 16 2014Two alternative interpretations of the quantum collapse are proposed: a time-ordered and a timeless one. The time-ordered interpretation implies that the speed of light can be defined in an absolute way, while the timeless quantum collapse implies relativity ... More
Comment on "Quantum theory cannot be extended" [arXiv:1005.5173v1]: Falsification of non-covariant extensions requires the before-before experimentJul 04 2010The Suarez-Scarani model is a non-covariant (frame-dependent) relativistic (time-ordered causal) nonlocal extension of quantum theory, which is not refuted by the experiments proposed in Reference [arXiv:1005.5173v1]. The covariant extensions considered ... More
The Hilton-Eckmann argument for cup-productsSep 03 2002We present a simple extension of the classical Hilton-Eckmann argument classically used to prove that the endomorphism monoid of the unit object in a monoidal category is commutative. It allows us to recover in a uniform way well-known results on the ... More
Does entanglement depend on the timing of the impacts at the beam-splitters?Apr 19 1997A new nonlocality experiment with moving beam-splitters is proposed. The experiment is analysed according to conventional quantum mechanics, and to an alternative nonlocal description in which superposition depends not only on indistinguishability but ... More
Algebra structure on the Hochschild cohomology of the ring of invariants of a Weyl algebra under a finite groupSep 10 2001Let $A_n$ be the $n$-th Weyl algebra, and let $G\subset\Sp_{2n}(\C)\subset\Aut(A_n)$ be a finite group of linear automorphisms of $A_n$. In this paper we compute the multiplicative structure on the Hochschild cohomology $\HH^*(A_n^G)$ of the algebra of ... More
Learning from history: Non-Markovian analyses of complex trajectories for extracting long-time behaviorJul 05 2014A number of modern sampling methods probe long time behavior in complex biomolecules using a set of relatively short trajectory segments. Markov state models (MSMs) can be useful in analyzing such data sets, but in particularly complex landscapes, the ... More
Second Yamabe Constant on Riemannian ProductsMay 05 2015Let $(M^m,g)$ be a closed Riemannian manifold $(m\geq 2)$ of positive scalar curvature and $(N^n,h)$ any closed manifold. We study the asymptotic behaviour of the second Yamabe constant and the second $N-$Yamabe constant of $(M\times N,g+th)$ as $t$ goes ... More
The transiting exoplanet host star GJ 436: a test of stellar evolution models in the lower main sequence, and revised planetary parametersOct 25 2007Knowledge of the stellar parameters for the parent stars of transiting exoplanets is pre-requisite for establishing the planet properties themselves, and often relies on stellar evolution models. GJ 436, which is orbited by a transiting Neptune-mass object, ... More
The Sun's Interior Metallicity Constrained by NeutrinosMay 25 2006Observed solar neutrino fluxes are employed to constrain the interior composition of the Sun. Including the effects of neutrino flavor mixing, the results from Homestake, Sudbury, and Gallium experiments constrain the Mg, Si, and Fe abundances in the ... More
The Astrometric-Spectroscopic Binary System HIP 50796: An Overmassive CompanionOct 14 2005We report spectroscopic observations of the star HIP 50796, previously considered (but later rejected) as a candidate member of the TW Hya association. Our measurements reveal it to be a single-lined binary with an orbital period of 570 days and an eccentricity ... More
A double-lined spectroscopic orbit for the young star HD 34700Nov 07 2003We report high-resolution spectroscopic observations of the young star HD 34700, which confirm it to be a double-lined spectroscopic binary. We derive an accurate orbital solution with a period of 23.4877 +/- 0.0013 days and an eccentricity of e = 0.2501 ... More
The structure of smooth algebras in Kapranov's framework for noncommutative geometryFeb 22 2000In Kapranov, M. {\it Noncommutative geometry based on commutator expansions,} J. reine angew. Math {\bf 505} (1998) 73-118, a theory of noncommutative algebraic varieties was proposed. Here we prove a structure theorem for the noncommutative coordinate ... More
Solar System chemical abundances corrected for systematicsJun 02 2014The relative chemical abundances between CI meteorites and the solar photosphere exhibit a significant trend with condensation temperature. A trend with condensation temperature is also seen when the solar photospheric abundances are compared to those ... More
Fundamental properties of lower main-sequence starsSep 06 2012The field of exoplanet research has revitalized interest in M dwarfs, which have become favorite targets of Doppler and transit surveys. Accurate measurements of their basic properties such as masses, radii, and effective temperatures have revealed significant ... More
Isoparametric functions and nodal solutions of the Yamabe equationJul 02 2018We prove existence results for nodal solutions of the Yamabe equation that are constant along the level sets of an isoparametric function.
Neutrino masses in the $SU(4)_L \otimes U(1)_X$ electroweak extension of the standard modelAug 30 2016We study the neutrino mass generation in the $SU(4)_L \otimes U(1)_X$ electroweak extension of the standard model by considering non-renormalizable dimension five effective operators. It is shown that there exist two topologies for the realizations of ... More
Parent Stars of Extrasolar Planets - XIV. Strong Evidence of Li Abundance DeficitOct 15 2014We report the results of our analysis of new high resolution spectra of 30 late-F to early-G dwarf field stars for the purpose of deriving their Li abundances. They were selected from the subsample of stars in the Valenti and Fischer compilation that ... More
Excision, descent, and singularity in algebraic $K$-theoryDec 05 2013Mar 05 2014Algebraic $K$-theory is a homology theory that behaves very well on sufficiently nice objects such as stable $C^*$-algebras or smooth algebraic varieties, and very badly in singular situations. This survey explains how to exploit this to detect singularity ... More
Some relationships between the geometry of the tangent bundle and the geometry of the Riemannian base manifoldDec 26 2009We compute the curvature tensor of the tangent bundle of a Riemannian manifold endowed with a natural metric and we get some relationships between the geometry of the base manifold and the geometry of the tangent bundle.
Twisted Kähler differential formsSep 12 2001We construct a braided structure on the algebra of K\"ahler differential forms of a commutative algebra twisted by an endomorphism. This generalises the construction done in M. Karoubi, Quantum Methods in Algebraic Topology, see, ... More
Intensity Mapping with the 21-cm and Lyman Alpha LinesJun 01 2012The 21-cm and Lyman Alpha lines are the dominant line-emission spectral features at opposite ends of the spectrum of hydrogen. Each line can be used to create three dimensional intensity maps of large scale structure. The sky brightness at low redshift ... More
Regularization of singularities in the weighted summation of Dirac-delta functions for the spectral solution of hyperbolic conservation laws?Nov 17 2016Singular source terms expressed as weighted summations of Dirac-delta functions are regularized through approximation theory with convolution operators. We consider the numerical solution of scalar and one-dimensional hyperbolic conservation laws with ... More
The Chemical Compositions of Stars with Planets: A ReviewSep 29 2006A number of trends among the properties of exoplanets have become evident in the years since the first one was announced in 1995. One particularly interesting trend began to emerge in 1997 -- the incidence of giant planets correlates with the metallicity ... More
The criticality of the Hantavirus infected phase at ZuniJul 02 2004A preliminary analysis of the temporal evolution of a population of \emph{Peromyscus maniculatus} infected with Hantavirus Sin Nombre is made. Ecological and epidemiological parameters are derived from the data, and they are used as inputs for the analytical ... More
Combining Astrometry and SpectroscopyDec 05 2003Orbital solutions for binary or multiple stellar systems that combine astrometry (e.g., position angles and angular separations) with spectroscopy (radial velocities) have important advantages over astrometric-only or spectroscopic-only solutions. In ... More
Algebraic v. topological K-theory: a friendly matchMar 24 2009These notes evolved from the lecture notes of a minicourse given in Swisk, the Sedano Winter School on K-theory held in Sedano, Spain, during the week January 22--27 of 2007, and from those of a longer course given in the University of Buenos Aires, during ... More
Monomorphisms between Cayley-Dickson AlgebrasDec 22 2005In this paper we study the algebra monomorphisms from A_m =R^(2^m) into A_n=R^(2^n) for 0<m<n where the A_k 's are the Cayley- Dickson algebras over the real numbers. We show that for m>2 there are many different types of monomorphisms and we describe ... More
Hopf construction map in higher dimensionsApr 07 2004In this paper, we study the zero set of the Hopf construction map F_n : A_n_ x A_n --> A_n x A_0 given by F_n (x, y) = (2xy, | y|^2 - |x|^2) for n >3 where A_n is the Cayley-Dickson algebra of dimension 2^n over the real numbers.
Ecological model of extinctionsSep 11 1996We present numerical results based on a simplified ecological system in evolution, showing features of extinction similar to that claimed for the biosystem on Earth. In the model each species consists of a population in interaction with the others, that ... More
The Exponential Map on the Cayley-Dickson algebrasMay 21 2004we study the exponential map for A_n = R^2^n, the Cayley_Dickson algebras for n bigher than 1,wich generalize the Complex exponential map to Quaternions,Octonions and so forth. As application,we show that the self-map of the unit sphere in A_n, S^(2^n)-1,given ... More
The Planet Host Star Gamma Cephei: Physical Properties, the Binary Orbit, and the Mass of the Substellar CompanionSep 22 2006The bright K1 III-IV star gamma Cep has been reported previously to have a companion in a 2.5-yr orbit that is possibly substellar, and also has a stellar companion at a larger separation that has never been seen. Here we determine for the first time ... More
The Multiple System HD 27638Dec 09 2005We report spectroscopic observations of HD 27638B, the secondary in a visual binary in which the physically associated primary (separation approximately 19 arcsec) is a B9V star. The secondary shows strong Li 6708 absorption suggesting youth, and has ... More
A formalism for the study of Natural Tensors Fields of type (0,2) on Manifolds and FibrationsDec 11 2008Dec 15 2009In order to study tensor fields of type (0,2) on manifolds and fibrations we introduce the notion of s-spaces. With the help of these objects we generalized the concept of natural tensor without making use of the theory of natural operators and differential ... More
Setting the Stage for Habitable PlanetsMar 26 2014Our understanding of the processes that are relevant to the formation and maintenance of habitable planetary systems is advancing at a rapid pace, both from observation and theory. The present review focuses on recent research that bears on this topic ... More
Interferometry and the Fundamental Properties of StarsJul 15 2011For many decades the determination of accurate fundamental parameters for stars (masses, radii, temperatures, luminosities, etc.) has mostly been the domain of eclipsing binary systems. That has begun to change as long-baseline interferometric techniques ... More
On the use of empirical bolometric corrections for starsAug 23 2010When making use of tabulations of empirical bolometric corrections for stars (BC_V), a commonly overlooked fact is that while the zero point is arbitrary, the bolometric magnitude of the Sun (Mbol_Sun) that is used in combination with such tables cannot ... More
A Revised Gyro-Age for M 67 from Kepler/K2-Campaign-5 Light CurvesSep 02 2016We revisit the photometric variability of stars in the M 67 field using Kepler/K2-Campaign-5 light curves. In our previous work, we limited the search area around M\,67 to that of a recent ground-based study. In the present work, we expand the search ... More
Infinitary propositional relevant languages with absurditySep 21 2018Analogues of Scott's isomorphism theorem, Karp's theorem as well as results on lack of compactness and strong completeness are established for infinitary propositional relevant logics. An "interpolation theorem" (of a particular sort introduced by Barwise ... More
Monomial ideals with large projective dimensionOct 14 2017Let S be a polynomial ring in n variables, over an arbitrary field. We give the total, graded, and multigraded Betti numbers of S/M, for every monomial ideal M in S. We also give an explicit characterization of all monomial ideals M in S for which the ... More
Parent Stars of Extrasolar Planets - XIII. Additional Evidence for Li Abundance AnomaliesApr 02 2014We report the results of our analysis of new high resolution spectra of 37 late-F to early-G dwarf stars for the purpose of deriving their Li abundances. Most of the stars were selected from the large Valenti and Fischer compilation and had unknown Li ... More
The obstruction to excision in K-theory and in cyclic homologyNov 08 2001Oct 03 2005Let $f:A \to B$ be a ring homomorphism of not necessarily unital rings and $I\triangleleft A$ an ideal which is mapped by f isomorphically to an ideal of B. The obstruction to excision in K-theory is the failure of the map between relative K-groups $K_*(A:I) ... More
The change in the inclination angle of the non-eclipsing binary SS Lacertae: future eclipsesDec 29 2000Eclipses in the 14.4-day period double-lined binary SS Lac were observed photographically and visually early in the 20th century, but stopped some 50 or 60 years ago. This has been explained by the presence of a distant third star in the system, which ... More
Astrometric-spectroscopic determination of the absolute masses of the HgMn binary star Phi HerculisMar 08 2007The Mercury-Manganese star Phi Her is a well known spectroscopic binary that has been the subject of a recent study by Zavala et al. (2006), in which they resolved the companion using long-baseline interferometry. The total mass of the binary is now fairly ... More
De Rham and infinitesimal cohomology in Kapranov's model for noncommutative algebraic geometryFeb 16 2001The title refers to the nilcommutative or $NC$-schemes introduced by M. Kapranov in math.AG/9802041. The latter are noncommutative nilpotent thickenings of commutative schemes. We consider also the parallel theory of nil-Poisson or $NP$-schemes, which ... More
Structural decomposition of monomial resolutionsJun 20 2017We express the multigraded Betti numbers of an arbitrary monomial ideal in terms of the multigraded Betti numbers of two basic classes of ideals. This decompo- sition has multiple applications. In some concrete cases, we use it to construct minimal resolutions ... More
Second Yamabe Constant on Riemannian ProductsMay 05 2015Dec 01 2016Let $(M^m,g)$ be a closed Riemannian manifold $(m\geq 2)$ of positive scalar curvature and $(N^n,h)$ any closed manifold. We study the asymptotic behaviour of the second Yamabe constant and the second $N-$Yamabe constant of $(M\times N,g+th)$ as $t$ goes ... More
Parent Stars of Extrasolar Planets. XV. Host Star Rotation Revisited with {\it Kepler} DataApr 21 2015We employed published rotation periods of {\it Kepler} field stars to test whether stars hosting planets tend to rotate more slowly than stars without known planets. Spectroscopic vsini observations of nearby stars with planets have indicated that they ... More
Variability Among Stars in the M 67 Field from Kepler/K2-Campaign-5 Light CurvesMar 21 2016We examine the photometric variability of stars in the M 67 field using Kepler/K2-Campaign-5 light curves. Variabilities and periods were determined for 639 stars. The mean photometric period of 28 single Sun-like members stars in M 67 is 23.4 +/- 1.2 ... More
Parent Stars of Extrasolar Planets. XII. Additional evidence for trends with vsini, condensation temperature, and chromospheric activityJun 24 2011Several recent studies have reported differences in vsini, abundance-condensation temperature trends, and chromospheric activity between samples of stars with and without Doppler-detected planets. These findings have been disputed, and the status of these ... More
Adaptive p-value weighting with power optimalityOct 03 2017Weighting the p-values is a well-established strategy that improves the power of multiple testing procedures while dealing with heterogeneous data. However, how to achieve this task in an optimal way is rarely considered in the literature. This paper ... More
Observational Constraints From Binary Stars on Stellar Evolution ModelsDec 04 2013Accurate determinations of masses and radii in binary stars, along with estimates of the effective temperatures, metallicities, and other properties, have long been used to test models of stellar evolution. As might be expected, observational constraints ... More
Cyclic homology, tight crossed products, and small stabilizationsApr 11 2013May 06 2013In \verb|arXiv:1212.5901| we associated an algebra $\Gami(\fA)$ to every bornological algebra $\fA$ and an ideal $I_{S(\fA)}\triqui\Gami(\fA)$ to every symmetric ideal $S\triqui\elli$. We showed that $I_{S(\fA)}$ has $K$-theoretical properties which are ... More
The order of dominance of a monomial idealFeb 13 2018Jan 10 2019Let S be a polynomial ring in n variables over a field, and let M be a monomial ideal of S. We introduce the notion of order of dominance of S/M, denoted odom(S/M), which has many similarities with the codimension of S/M. In particular, we show that odom(S/M) ... More
The QED lowest-order radiative corrections to the two polarized identical fermion scatteringDec 03 1999The explicit exact expressions of QED lowest-order radiative corrections to the two polarized identical fermion scattering are presented in covariant form. Polarization effects are treated in detail. The infrared divergence from the real photon emission ... More
Radiative Corrections to Moller Scattering of Polarized ParticlesDec 17 1997Principal contributions to QED radiative effects for Moller scattering of polarized particles are investigated both on the Born level and taking into account radiative corrections (RC). Scattering on the case of longitudinal and transversal polarized ... More
In whose mind is Mathematics an "a priori cognition"?Sep 22 2008According to the philosopher Kant, Mathematics is an "a priori cognition". Kant's assumption, together with the unsolvability of Hilbert's 10th problem, implies an astonishing result.
Bases of Wormholes in Quantum CosmologyApr 24 1994We show that if the space of physical states spanned by the wormhole wave functions can be equipped with a Hilbert structure, such a Hilbert space must coincide with that of the Lorentzian gravitational system under consideration. The physical inner product ... More
Relative Chern characters for nilpotent idealsJul 11 2008Sep 17 2008If I is a nilpotent ideal in a $\mathbb{Q}$-algebra $A$, Goodwillie defined two isomorphisms from $K_*(A,I)$ to negative cyclic homology, $HN_*(A,I)$. One is the relative version of the absolute Chern character, and the other is defined using rational ... More
MHD Models of Planetary Nebulae: ReviewFeb 01 2002Hydrodynamical (HD) simulations played an important role in understanding the dynamics and shaping of Planetary Nebulae (PNe) in the past century. However, HD solutions are just a first order approach. The new millennium arrives with the generalized understanding ... More
Complex structures in generalized small worldsFeb 23 2001We propose a generalization of small world networks, in which the reconnection of links is governed by a function that depends on the distance between the elements to be linked. An adequate choice of this function lets us control the clusterization of ... More
Extent of the Immirzi Ambiguity in Quantum General RelativityMar 07 2002The Ashtekar-Barbero formulation of general relativity admits a one-parameter family of canonical transformations that preserves the expressions of the Gauss and diffeomorphism constraints. The loop quantization of the connection formalism based on each ... More
Detailed abundance analysis of 8 super-metal-rich star candidatesDec 16 2000We provide detailed abundance analyses of 8 candidate super-metal-rich stars. Five of them are confirmed to have [Fe/H] > 0.2 dex, the generally-accepted limit for super-metal-richness. Furthermore, we derive abundances of several elements and find that ... More
On the Arithmetic determination of the traceAug 09 2013Oct 17 2015Let $K$ be a number field, which is tame and non totally real. In this article we give a numerical criterion, depending only on the ramification behavior of ramified primes in $K$, to decide whether or not the integral trace of $K$ is isometric to the ... More
Statistical Compressed Sensing of Gaussian Mixture ModelsJan 30 2011A novel framework of compressed sensing, namely statistical compressed sensing (SCS), that aims at efficiently sampling a collection of signals that follow a statistical distribution, and achieving accurate reconstruction on average, is introduced. SCS ... More
The Search for signals of technological activities in the galaxyDec 12 2010In this article an analysis of the fundamentals used to search for extraterrestrial artificial signals in the galaxy, which have been developing for more than five decades, is presented. It is shown that the key factor for the success of these research ... More
Photodissociation in proto-planetary nebulae. Hydrodynamical simulations and solutions for low-velocity multi-lobesSep 10 2010We explore the effects of photodissociation at the stages of post-asymptotic giant branch stars to find a mechanism able to produce multi-polar shapes. We perform two-dimensional gasdynamical simulations to model the effects of photodissociation in proto-planetary ... More
Science for Peace in the Benefit of Humankind. The Hippocratic Oath for Scientists conceptJun 17 2010This article shows the importance that has had the scientific research, the technological development and the innovation processes in increasing the lethality of the available weapons during the last century. A set of initiatives promoted by the scientific ... More
On a question of Perlis and Stuart regarding arithmetic equivalenceJul 09 2018Let $K$ be a number field. The $K$-arithmetic type of a rational prime $\ell$ is the tuple $A_{K}(\ell)=(f^{K}_{1},...,f^{K}_{g_{\ell}})$ of the residue degrees of $\ell$ in $K$, written in ascending order. A well known result of Perlis from the 70's ... More
Nonparametric Learning and Optimization with CovariatesMay 03 2018Nov 09 2018Modern decision analytics frequently involves the optimization of an objective over a finite horizon where the functional form of the objective is unknown. The decision analyst observes covariates and tries to learn and optimize the objective by experimenting ... More
Nonnegative Matrix Underapproximation for Robust Multiple Model FittingNov 04 2016Apr 10 2017In this work, we introduce a highly efficient algorithm to address the nonnegative matrix underapproximation (NMU) problem, i.e., nonnegative matrix factorization (NMF) with an additional underapproximation constraint. NMU results are interesting as, ... More
On the instability of two entropic dynamical modelsAug 27 2016In this paper we study two entropic dynamical models from the viewpoint of information geometry. We study the geometry structures of the associated statistical manifolds. In order to analyse the character of the instability of the systems, we obtain their ... More
Comparing binary systems from rotating parent gas structures with different total massesJan 25 2017In this paper we continue the investigation reported by \cite{RMAA} concerning the morphology of binary configurations obtained via the collapse of rotating parent gas structures with total masses in the range of M$_T$= 1 to 5 M$_{\odot}$. Here we extend ... More
Pile-up corrections in laser-driven pulsed x-ray sourcesNov 22 2016May 31 2018A formalism for treating the pile-up produced in solid-state detectors by laser-driven pulsed x-ray sources has been developed. It allows the direct use of x-ray spectroscopy without artificially decreasing the number of counts in the detector, assuming ... More
On the complete bounds of $L_p$-Schur multipliersFeb 21 2019We study the class $\mathcal{M}_p$ of Schur multipliers on the Schatten-von Neumann class $\mathcal{S}_p$ with $1 \leq p \leq \infty$ as well as the class of completely bounded Schur multipliers $\mathcal{M}_p^{cb}$. We first show that for $2 \leq p < ... More
Analysis of the 2004 Venezuela Referendum: The Official Results Versus the Petition SignaturesMay 23 2012On August 15th, 2004, Venezuelans had the opportunity to vote in a Presidential Recall Referendum to decide whether or not President Hugo Ch\'{a}vez should be removed from office. The process was largely computerized using a touch-screen system. In general ... More
Robust Estimators in Partly Linear Regression Models on Riemannian ManifoldsAug 03 2010May 25 2011Under a partially linear models we study a family of robust estimates for the regression parameter and the regression function when some of the predictor variables take values on a Riemannian manifold. We obtain the consistency and the asymptotic normality ... More
On row sequences of Padé and Hermite-Padé approximationFeb 13 2015A survey of direct and inverse type results for row sequences of Pad\'e and Hermite-Pad\'e approximation is given. A conjecture is posed on an inverse type result for type II Hermite-Pad\'e approximation when it is known that the sequence of common denominators ... More
The role of rotation on Petersen Diagrams. II The influence of near-degeneracySep 13 2007In the present work, the effect of near-degeneracy on rotational Petersen diagrams (RPD) is analysed. Seismic models are computed considering rotation effects on both equilibrium models and adiabatic oscillation frequencies (including second-order near-degeneracy ... More
Quantum Mechanics of the Early Universe and its Limiting TransitionFeb 28 2003Aug 30 2003In this paper Quantum Mechanics with Fundamental Length is chosen as the theory for describing the early Universe. This is possible due to the presence in the theory of General Uncertainty Relations from which unavoidable it follows that in nature a fundamental ... More
Tuning the conductance of molecular junctions: transparent versus tunneling regimesOct 10 2008Oct 14 2008We present a theoretical study of the transport characteristics of molecular junctions, where first-row diatomic molecules are attached to (001) gold and platinum electrodes. We find that the conductance of all of these junctions is of the order of the ... More
Nonnegative Matrix Underapproximation for Robust Multiple Model FittingNov 04 2016In this work, we introduce the first algorithm to truly address the nonnegative matrix underapproximation (NMU) problem, i.e., nonnegative matrix factorization (NMF) with an additional underapproximation constraint. NMU results are interesting as, compared ... More
Fast L1-NMF for Multiple Parametric Model EstimationOct 18 2016In this work we introduce a comprehensive algorithmic pipeline for multiple parametric model estimation. The proposed approach analyzes the information produced by a random sampling algorithm (e.g., RANSAC) from a machine learning/optimization perspective, ... More
Involutions on the Algebra of Physical Observables From Reality ConditionsJun 20 1995Some aspects of the algebraic quantization programme proposed by Ashtekar are revisited in this article. It is proved that, for systems with first-class constraints, the involution introduced on the algebra of quantum operators via reality conditions ... More
CANONICAL QUANTIZATION OF CYLINDRICALLY SYMMETRIC MODELSApr 05 1995We carry out the canonical quantization of the Levi-Civit\`a family of static and cylindrical solutions. The reduced phase space of this family of metrics is proved to coincide with that corresponding to the Kasner model, including the associated symplectic ... More
Reality Conditions for Lorentzian and Euclidean Gravity in the Ashtekar FormulationNov 11 1993Using Ashtekar variables, we analyze Lorentzian and Euclidean gravity in vacuum up to a constant conformal transformation. We prove that the reality conditions are invariant under a Wick rotation of the time, and show that the compatibility of the algebra ... More
The zero divisors of the Cayley-Dickson algebras over the real numbersOct 08 1997In this paper we describe algebraically the zero divirsors of the Cayley- Dickson algebras $\a_{n}=\erre^{2^n}$ for $n \ge 4$ over the real numbers.
Fluid accretion onto relativistic stars and gravitational radiationAug 15 2004This article reports results from numerical simulations of the gravitational radiation emitted from nonrotating relativistic stars as a result of the axisymmetric accretion of layers of perfect fluid matter, shaped in the form of quadrupolar shells. We ... More
Rotating Relativistic Thin Disks as Sources of the Taub-NUT SolutionDec 11 2002Jun 14 2009Rotating disks with nonzero radial pressure and finite radius are studied. The models are based in the Taub-NUT metric and constructed using the well-known ``displace, cut and reflect'' method. We find that the disks are made of perfect fluids with constant ... More
A straightforward local-search optimization algorithm on the symmetric groupApr 29 2009Given a real objective function defined over the symmetric group, a direct local-search algorithm is proposed, and its complexity is estimated. In particular for an $n$-dimensional unit vector we are interested in the permutation isometry that acts on ... More