Results for "Esteban Vazquez-Fernandez"

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Generalized Presentation Attack Detection: a face anti-spoofing evaluation proposalApr 12 2019Over the past few years, Presentation Attack Detection (PAD) has become a fundamental part of facial recognition systems. Although much effort has been devoted to anti-spoofing research, generalization in real scenarios remains a challenge. In this paper ... More
Magnetization pinning in modulated nanowires: from topological protection to the "corkscrew" mechanismJan 02 2018Diameter-modulated nanowires offer an important paradigm to design the magnetization response of 3D magnetic nanostructures by engineering the domain wall pinning. With the aim to understand its nature and to control the process, we analyze the magnetization ... More
Time-Series Analysis via Low-Rank Matrix Factorization Applied to Infant-Sleep DataApr 09 2019Apr 10 2019We propose a nonparametric model for time series with missing data based on low-rank matrix factorization. The model expresses each instance in a set of time series as a linear combination of a small number of shared basis functions. Constraining the ... More
The Why of the applicability of Statistical Physics to EconomicsSep 11 2006Apr 24 2007We analyze the relationships between game theory and quantum mechanics and the extensions to statistical physics and information theory. We use certain quantization relationships to assign quantum states to the strategies of a player. These quantum states ... More
A hydrodynamic approach to boost invariant free streamingFeb 21 2014Aug 10 2015We consider a family of exact boost invariant solutions of the transport equation for free streaming massless particles, where the one particle distribution function is defined in terms of a function of a single variable. The evolution of second and third ... More
Non abelian hydrodynamics and heavy ion collisionsNov 07 2013The goal of the relativistic heavy ion collisions (RHIC) program is to create a state of matter where color degrees of freedom are deconfined. The dynamics of matter in this state, in spite of the complexities of quantum chromodynamics, is largely determined ... More
EGT through Quantum Mechanics & from Statistical Physics to EconomicsApr 30 2007By analyzing the relationships between a socioeconomical system modeled through evolutionary game theory and a physical system modeled through quantum mechanics we show how although both systems are described through two theories apparently different ... More
An extension of the momentum transfer model to time-dependent pipe turbulenceSep 20 2011Jan 10 2012We analyze a possible extension of Gioia and Chakraborty's momentum transfer model of friction in steady turbulent pipe flows (Phys. Rev. Lett. 96, 044502 (2006)) to the case of time and/or space dependent turbulent flows. The end result is an expression ... More
Internal Fluctuations Effects on Fisher WavesMay 02 2001May 03 2001We study the diffusion-limited reaction A + A <-> A in different spatial dimensions to observe the effect of internal fluctuations on the interface between stable and unstable phases. We find that, similar to what has been observed in d=1 dimensions, ... More
Friction factor for turbulent flow in rough pipes from Heisenberg's closure hypothesisJan 02 2009Apr 17 2009We show that the main results of the analysis of the friction factor for turbulent pipe flow reported in G. Gioia and P. Chakraborty (GC), Phys. Rev. Lett. 96, 044502 (1996) can be recovered by assuming the Heisenberg closure hypothesis for the turbulent ... More
Collapse times for attractive Bose-Einstein condensatesAug 24 2007Oct 25 2007We argue that the main mechanism for condensate collapse in an attractive Bose-Einstein condensate is the loss of coherence between atoms a finite distance apart, rather than the growth of the occupation number in noncondensate modes. Since the former ... More
Noise induced inflationNov 19 1998We consider a closed Friedmann-Robertson-Walker Universe driven by the back reaction from a massless, non-conformally coupled quantum scalar field. We show that the back-reaction of the quantum field is able to drive the cosmological scale factor over ... More
Electron neutrino opacity in magnetised mediaNov 03 1997We study the effects of strong magnetic fields ($B> 10^{13}$~G) in the cross section for $\nu_e n\to p e$ scattering in the presence of a degenerate electron background. This can be relevant for the $\nu_e$ propagation in the proto-neutron star stage ... More
Relativistic fluctuating hydrodynamicsAug 20 1997Nov 18 1997We derive the formulae of fluctuating hydrodynamics appropiate to a relativistically consistent divergence type theory, obtaining Landau - Lifshitz fluctuating hydrodynamics as a limiting case.
Discreteness Effects in Population DynamicsDec 04 2015Mar 11 2016We analyse numerically the effects of small population size in the initial transient regime of a simple example population dynamics. These effects play an important role for the numerical determination of large deviation functions of additive observables ... More
Nonpositively curved metric in the positive cone of a finite von Neumann algebraAug 13 2008In this paper we study the metric geometry of the space $\Sigma$ of positive invertible elements of a von Neumann algebra ${\mathcal A}$ with a finite, normal and faithful tracial state $\tau$. The trace induces an incomplete Riemannian metric $<x,y>_a=\tau ... More
A Hydrodynamic Approach to the Study of Anisotropic Instabilities in Dissipative Relativistic PlasmasFeb 04 2016Sep 29 2016We develop a purely hydrodynamic formalism to describe collisional, anisotropic instabilities in a relativistic plasma, that are usually described with kinetic theory tools. Our main motivation is the fact that coarse-grained models of high particle number ... More
Schmidt decomposable products of projectionsJun 15 2017We characterize operators $T=PQ$ ($P,Q$ orthogonal projections in a Hilbert space $H$) which have a singular value decomposition. A spatial characterizations is given: this condition occurs if and only if there exist orthonormal bases $\{\psi_n\}$ of ... More
Lagrangian Grassmannian in Infinite DimensionAug 16 2008Given a complex structure $J$ on a real (finite or infinite dimensional) Hilbert space $H$, we study the geometry of the Lagrangian Grassmannian $\Lambda(H)$ of $H$, i.e. the set of closed linear subspaces $L\subset H$ such that $$J(L)=L^\perp.$$ The ... More
Selecting interesting zones at Aburrá valley and St. Nicholas Valley's using the identification method of Density-based Clustering and Improved Nearest Neighbor applied on social networksJun 09 2014Nov 15 2016More than ever, social networks have become an important place in the interaction and behaviour of humans in the last decade. This valuable position makes it imperative to analyze different aspects of everyday life and science in general. This paper illustrates ... More
Decoherence in the cosmic background radiationMar 01 2011Apr 28 2011In this paper we analyze the possibility of detecting nontrivial quantum phenomena in observations of the temperature anisotropy of the cosmic background radiation (CBR), for example, if the Universe could be found in a coherent superposition of two states ... More
Primordial Magnetic Field Amplification from Turbulent ReheatingApr 12 2010Jul 05 2010We analyze the possibility of primordial magnetic field amplification by a stochastic large scale kinematic dynamo during reheating. We consider a charged scalar field minimally coupled to gravity. During inflation this field is assumed to be in its vacuum ... More
Erratum : Existence of 3D Skyrmions. Complete versionJan 25 2004This erratum corrects the proof given in \cite{E1,E2} about the existence of $ 3D $ Skyrmions. This is done by changing the arguments of the proof while remaining in the same framework of concentration-compactness. Note however that the use of this method ... More
Macroscopic description of preheatingSep 16 2003Sep 17 2003We present a macroscopic model of the decay of a coherent classical scalar field into statistical fluctuations through the process of parametric amplification. We solve the field theory (henceforth,"microscopic") model to leading order in a Large N expansion, ... More
Relativistic theories of interacting fields and fluidsDec 29 2000Mar 19 2001We investigate divergence-type theories (DTT) describing the dissipative interaction between a field and a fluid. We look for theories which, under equilibrium conditions, reduce to the theory of a Klein-Gordon scalar field and a perfect fluid. We show ... More
Analytical results for a continuum model of crystalline tensionless surfaces. I. Variational mean field studyDec 01 1999We study analytically the equilibrium and near-equilibrium properties of a model of surfaces relaxing via linear surface diffusion and subject to a lattice potential. We employ the variational mean field formalism introduced by Saito for the study of ... More
Neutrino MassesDec 12 1994This is a review for Reports of Progress in Physics. After an introduction we start by explaining the different neutrino masses corresponding to different types of neutrinos, Dirac or Majorana, in section 2. In section 3 we discuss the main elementary ... More
Quantum Games EntropyJun 06 2006Dec 08 2016We propose the study of quantum games from the point of view of quantum information theory and statistical mechanics. Every game can be described by a density operator, the von Neumann entropy and the quantum replicator dynamics. There exists a strong ... More
Real time approach to tunneling in open quantum systems: decoherence and anomalous diffusionMar 06 2006Macroscopic quantum tunneling is described using the master equation for the reduced Wigner function of an open quantum system at zero temperature. Our model consists of a particle trapped in a cubic potential interacting with an environment characterized ... More
On the capture rates of big bang neutrinos by nuclei within the Dirac and Majorana hypothesesOct 01 2018The capture rates of non-relativistic neutrinos on beta decaying nuclei depends on whether their mass is Dirac or Majorana. It is known that for relic neutrinos from the big-bang, and within minimal assumptions, the rate is a factor two larger in the ... More
Progress in high-energy cosmic ray physicsOct 30 2017We review some of the recent progress in our knowledge about high-energy cosmic rays, with an emphasis on the interpretation of the different observational results. We discuss the effects that are relevant to shape the cosmic ray spectrum and the explanations ... More
The role of disease cycles in the endemicity of infectious diseasesFeb 08 2017Vector-borne diseases with reservoir cycles are complex to understand because new infections come from contacts of the vector with humans and different reservoirs. In this scenario, the basic reproductive number $\mathcal{R}^h_0$ of the system where the ... More
Kicked neutron stars and microlensingSep 02 1996Due to the large kick velocities with which neutron stars are born in supernovae explosions, their spatial distribution is more extended than that of their progenitor stars. The large scale height of the neutron stars above the disk plane makes them potential ... More
Computer proof of ergodicity breaking in expanding coupled mapsMar 12 2019From a dynamical viewpoint, basic phase transitions of statistical mechanics can be regarded as some ergodicity breaking. While many random models exhibiting such transitions exist, deterministic examples, which would only use chaotic dynamics as the ... More
Self-adjointness of Dirac operators via Hardy-Dirac inequalitiesJun 09 2007Distinguished selfadjoint extensions of Dirac operators are constructed for a class of potentials including Coulombic ones up to the critical case, $-|x|^{-1}$. The method uses Hardy-Dirac inequalities and quadratic form techniques.
Prototypal Analysis and Prototypal RegressionJan 31 2017Aug 23 2017Prototypal analysis is introduced to overcome two shortcomings of archetypal analysis: its sensitivity to outliers and its non-locality, which reduces its applicability as a learning tool. Same as archetypal analysis, prototypal analysis finds prototypes ... More
Existence and Stability of Steady Fronts in Bistable CMLNov 07 1995We prove the existence and we study the stability of the kink-like fixed points in a simple Coupled Map Lattice for which the local dynamics has two stable fixed points. The condition for the existence allows us to define a critical value of the coupling ... More
Results from DELPHI on the searches for SM and MSSM Neutral Higgs bosonsJul 01 2003These final results from DELPHI searches for the Standard Model SM Higgs boson, together with benchmark scans of the Minimal Supersymmetric Standard Model MSSM neutral Higgs bosons, used data taken at centre-of-mass energies between 200 and 209GeV with ... More
A complex analysis approach to Atangana-Baleanu fractional calculusMay 16 2019The standard definition for the Atangana-Baleanu fractional derivative involves an integral transform with a Mittag-Leffler function in the kernel. We show that this integral can be rewritten as a complex contour integral which can be used to provide ... More
Results on Proton-Irradiated 3D Pixel Sensors Interconnected to RD53A Readout ASICMar 29 2019Test beam results obtained with 3D pixel sensors bump-bonded to the RD53A prototype readout ASIC are reported. Sensors from FBK (Italy) and IMB-CNM (Spain) have been tested before and after proton-irradiation to an equivalent fluence of about $1$ $\times$ ... More
An elliptic regularity theorem for fractional partial differential operatorsApr 03 2018We present and prove a version of the elliptic regularity theorem for partial differential equations involving fractional Riemann-Liouville derivatives. In this case, regularity is defined in terms of Sobolev spaces $H^s(X)$: if the forcing of a linear ... More
Kinks Dynamics in One-Dimensional Coupled Map LatticesOct 20 1994We examine the problem of the dynamics of interfaces in a one-dimensional space-time discrete dynamical system. Two different regimes are studied : the non-propagating and the propagating one. In the first case, after proving the existence of such solutions, ... More
Near Real-Time Object Recognition for Pepper based on Deep Neural Networks Running on a BackpackNov 20 2018The main goal of the paper is to provide Pepper with a near real-time object recognition system based on deep neural networks. The proposed system is based on YOLO (You Only Look Once), a deep neural network that is able to detect and recognize objects ... More
A new integral loss function for Bayesian optimizationAug 20 2014We consider the problem of maximizing a real-valued continuous function $f$ using a Bayesian approach. Since the early work of Jonas Mockus and Antanas \v{Z}ilinskas in the 70's, the problem of optimization is usually formulated by considering the loss ... More
Systems with two symmetric absorbing states: relating the microscopic dynamics with the macroscopic behaviorOct 08 2008We propose a general approach to study spin models with two symmetric absorbing states. Starting from the microscopic dynamics on a square lattice, we derive a Langevin equation for the time evolution of the magnetization field, that successfully explains ... More
On the almost sure central limit theorem for ARX processes in adaptive trackingNov 21 2018The goal of this paper is to highlight the almost sure central limit theorem for martingales to the control community and to show the usefulness of this result for the system identification of controllable ARX(p,q) process in adaptive tracking. We also ... More
Symmetry and symmetry breaking: rigidity and flows in elliptic PDEsNov 30 2017The issue of symmetry and symmetry breaking is fundamental in all areas of science. Symmetry is often assimilated to order and beauty while symmetry breaking is the source of many interesting phenomena such as phase transitions, instabilities, segregation, ... More
Barenblatt solutions and asymptotic behaviour for a nonlinear fractional heat equation of porous medium typeMay 29 2012Sep 13 2012We establish the existence and uniqueness of fundamental solutions for the fractional porous medium equation introduced in \cite{PQRV1}. They are self-similar functions of the form $u(x,t)= t^{-\alpha} f(|x|\,t^{-\beta})$ with suitable $\alpha$ and $\beta$. ... More
Transient convective instabilities in directional solidificationMay 28 2010Nov 10 2010We study the convective instability of the melt during the initial transient in a directional solidification experiment in a vertical configuration. We obtain analytically the dispersion relation, and perform an additional asymptotic expansion for large ... More
On the abundance discrepancy problem in HII regionsJul 24 2007The origin of the abundance discrepancy is one of the key problems in the physics of photoionized nebula. In this work, we analize and discuss data for a sample of Galactic and extragalactic HII regions where this abundance discrepancy has been determined. ... More
Self-adjointness via partial Hardy-like inequalitiesMay 30 2008Distinguished selfadjoint extensions of operators which are not semibounded can be deduced from the positivity of the Schur Complement (as a quadratic form). In practical applications this amounts to proving a Hardy-like inequality. Particular cases are ... More
Information diffusion epidemics in social networksJun 05 2007The dynamics of information dissemination in social networks is of paramount importance in processes such as rumors or fads propagation, spread of product innovations or "word-of-mouth" communications. Due to the difficulty in tracking a specific information ... More
Option Pricing, Historical Volatility and Tail RisksFeb 06 2014We revisit the problem of pricing options with historical volatility estimators. We do this in the context of a generalized GARCH model with multiple time scales and asymmetry. It is argued that the reason for the observed volatility risk premium is tail ... More
Existence of maximal solutions for some very singular nonlinear fractional diffusion equations in 1DMay 19 2015We consider nonlinear parabolic equations involving fractional diffusion of the form $\partial_t u + (-\Delta)^s \Phi(u)= 0,$ with $0<s<1$, and solve an open problem concerning the existence of solutions for very singular nonlinearities $\Phi$ in power ... More
Reconstructing 1/2 BPS Space-Time Metrics from Matrix Models and Spin ChainsDec 01 2006Using the AdS/CFT correspondence, we address the question of how to measure complicated space-time metrics using gauge theory probes. In particular, we consider the case of the 1/2 BPS geometries of type IIB supergravity. These geometries are classified ... More
Constraining Modified Gravity with Large non-GaussianitiesJun 03 2008Jun 17 2008In writing a covariant effective action for single field inflation, one is allowed to add a Gauss-Bonnet and axion-type curvature couplings. These couplings represent modifications of gravity, and are the unique higher-curvature terms that lead to second ... More
Black Hole Production from High Energy Scattering in AdS/CFTSep 21 2007In this article we show how to set up initial states in ${\cal N} =4$ SYM theory that correspond to high energy graviton collisions, leading to black hole formation in $AdS_5\times S^5$. For this purpose, we study states in the gauge theory that are dual ... More
Ultimate Fate of Constrained VotersMay 27 2004Jul 13 2004We determine the ultimate fate of individual opinions in a socially-interacting population of leftists, centrists, and rightists. In an elemental interaction between agents, a centrist and a leftist can become both centrists or both become leftists with ... More
The $SU(3)$ $A_1$ graph and its associated quantum groupoidDec 20 2018An explicit and complete construction of the $SU(3)$ $A_1$ associated quantum groupoid is presented in this work, inspired by the approach taken by Trinchero for the $SU(2)$ $A_l$ graphs. New creation and annihilation operators were defined in order to ... More
Relativistic hydrogenic atoms in strong magnetic fieldsJul 02 2006In the Dirac operator framework we characterize and estimate the ground state energy of relativistic hydrogenic atoms in a constant magnetic field and describe the asymptotic regime corresponding to a large field strength using relativistic Landau levels. ... More
Notes on TQFT Wire Models and Coherence Equations for SU(3) Triangular CellsJul 05 2010Dec 28 2010After a summary of the TQFT wire model formalism we bridge the gap from Kuperberg equations for SU(3) spiders to Ocneanu coherence equations for systems of triangular cells on fusion graphs that describe modules associated with the fusion category of ... More
Super-linear elliptic equation for the Pucci operator without growth restrictions for the dataDec 09 2007In this paper we deal with existence and uniqueness of solution to super-linear problems for the Pucci operator: $$ -\M^+(D^2u)+|u|^{s-1}u=f(x) \quad {in} \RR^n, $$ where $s>1$ and $f$ satisfies only local integrability conditions. This result is well ... More
Keller-Lieb-Thirring inequalities for Schrödinger operators on cylindersMar 30 2015Jun 11 2015This note is devoted to Keller-Lieb-Thirring spectral estimates for Schr\"odinger operators on infinite cylinders: the absolute value of the ground state level is bounded by a function of a norm of the potential. Optimal potentials with small norms are ... More
Gauge Invariance, Geometry and ArbitrageAug 21 2009In this work, we identify the most general measure of arbitrage for any market model governed by It\^o processes. We show that our arbitrage measure is invariant under changes of num\'{e}raire and equivalent probability. Moreover, such measure has a geometrical ... More
The Fisher-KPP problem with doubly nonlinear "fast" diffusionJul 05 2016The famous Fisher-KPP reaction diffusion model combines linear diffusion with the typical Fisher-KPP reaction term, and appears in a number of relevant applications. It is remarkable as a mathematical model since, in the case of linear diffusion, it possesses ... More
A proof of uniform convergence over time for a distributed particle filterApr 05 2015Nov 24 2015Distributed signal processing algorithms have become a hot topic during the past years. One class of algorithms that have received special attention are particles filters (PFs). However, most distributed PFs involve various heuristic or simplifying approximations ... More
Hydrodynamic Limit of Nonlinear Diffusions with Fractional Laplacian OperatorsMay 29 2012Jun 28 2012In the limit of a nonlinear diffusion model involving the fractional Laplacian we get a "mean field" equation arising in superconductivity and superfluidity. For this equation, we obtain uniqueness, universal bounds and regularity results. We also show ... More
Higher-order supersymmetric quantum mechanicsFeb 15 2005Feb 17 2005We review the higher-order supersymmetric quantum mechanics (H-SUSY QM), which involves differential intertwining operators of order greater than one. The iterations of first-order SUSY transformations are used to derive in a simple way the higher-order ... More
Automatic Taxonomy Extraction from Query Logs with no Additional Sources of InformationOct 02 2015Oct 05 2015Search engine logs store detailed information on Web users interactions. Thus, as more and more people use search engines on a daily basis, important trails of users common knowledge are being recorded in those files. Previous research has shown that ... More
A weighted Moser-Trudinger inequality and its relation to the Caffarelli-Kohn-Nirenberg inequalities in two space dimensionsMar 29 2007We first prove a weighted inequality of Moser-Trudinger type depending on a parameter, in the two-dimensional Euclidean space. The inequality holds for radial functions if the parameter is larger than -1. Without symmetry assumption, it holds if and only ... More
Multiplicity results for the assigned Gauss curvature problem in R2Sep 23 2008To study the problem of the assigned Gauss curvature with conical singularities on Riemanian manifolds, we consider the Liouville equation with a single Dirac measure on the two-dimensional sphere. By a stereographic projection, we reduce the problem ... More
Characterization of the critical magnetic field in the Dirac-Coulomb equationDec 24 2007We consider a relativistic hydrogenic atom in a strong magnetic field. The ground state level depends on the strength of the magnetic field and reaches the lower end of the spectral gap of the Dirac-Coulomb operator for a certain critical value, the critical ... More
Nonlinear Eigenvalues and Bifurcation Problems for Pucci's OperatorSep 17 2004In this paper we extend existing results concerning generalized eigenvalues of Pucci's extremal operators. In the radial case, we also give a complete description of their spectrum, together with an equivalent of Rabinowitz's Global Bifurcation Theorem. ... More
Asymptotic behaviour of the doubly nonlinear equation $u_t=Δ_p u^m$ on bounded domainsJun 07 2012We study the homogeneous Dirichlet problem for the doubly nonlinear equation $u_t = \Delta_p u^m$, where $p>1,\ m>0$ posed in a bounded domain in $\mathbb{R}^N$ with homogeneous boundary conditions and with non-negative and integrable data. In this paper ... More
Quantitative Local and Global A Priori Estimates for Fractional Nonlinear Diffusion EquationsOct 09 2012Oct 07 2013We establish quantitative estimates for solutions $u(t,x)$ to the fractional nonlinear diffusion equation, $\partial_t u +(-\Delta)^s (u^m)=0$ in the whole range of exponents $m>0$, $0<s<1$. The equation is posed in the whole space $x\in\mathbb{R}^d$. ... More
Positivity, local smoothing, and Harnack inequalities for very fast diffusion equationsMay 30 2008Dec 01 2008We investigate qualitative properties of local solutions $u(t,x)\ge 0$ to the fast diffusion equation, $\partial_t u =\Delta (u^m)/m$ with $m<1$, corresponding to general nonnegative initial data. Our main results are quantitative positivity and boundedness ... More
Asymptotic behaviour of a porous medium equation with fractional diffusionApr 07 2010We consider a porous medium equation with nonlocal diffusion effects given by an inverse fractional Laplacian operator. In a previous paper we have found mass-preserving, nonnegative weak solutions of the equation satisfying energy estimates. The equation ... More
Estimation of the volume of an excursion set of a Gaussian process using intrinsic KrigingNov 09 2006Assume that a Gaussian process $\xi$ is predicted from $n$ pointwise observations by intrinsic Kriging and that the volume of the excursion set of $\xi$ above a given threshold $u$ is approximated by the volume of the predictor. The first part of this ... More
Finite-Time and -Size Scalings in the Evaluation of Large Deviation Functions - Part II: Numerical Approach in Continuous TimeJul 29 2016Rare trajectories of stochastic systems are important to understand -- because of their potential impact. However, their properties are by definition difficult to sample directly. Population dynamics provide a numerical tool allowing their study, by means ... More
Finite-Time and -Size Scalings in the Evaluation of Large Deviation Functions - Part I: Analytical Study using a Birth-Death ProcessJul 16 2016Oct 25 2016The Giardin\`a-Kurchan-Peliti algorithm is a numerical procedure that uses population dynamics in order to calculate large deviation functions associated to the distribution of time-averaged observables. To study the numerical errors of this algorithm, ... More
Finite-Time and -Size Scalings in the Evaluation of Large Deviation Functions - Part II: Numerical Approach in Continuous TimeJul 29 2016Oct 25 2016Rare trajectories of stochastic systems are important to understand -- because of their potential impact. However, their properties are by definition difficult to sample directly. Population dynamics provide a numerical tool allowing their study, by means ... More
Interpolation inequalities on the sphere: linear vs. nonlinear flowsSep 30 2015Oct 24 2015This paper is devoted to sharp interpolation inequalities on the sphere and their proof using flows. The method explains some rigidity results and proves uniqueness in related semilinear elliptic equations. Nonlinear flows allow to cover the interval ... More
Entanglement properties of a two spin-one particle system under a Lorentz transformationOct 05 2012We analize the entanglement change, under a Lorentz transformation, of a system consisting of two spin-one particles, considering different partitions of the Hilbert space, which has spin and momentum degrees of freedom. We show that there exists a complete ... More
Massive star formation in Wolf-Rayet galaxies. IV: Colours, chemical composition analysis and metallicity-luminosity relationsApr 05 2010Apr 29 2010(Abridged) We performed a multiwavelength analysis of a sample of starburst galaxies that show the presence of a substantial population of very young massive (WR) stars. Here we present the global analysis of the derived photometric and chemical properties. ... More
Quantum space-time of a charged black holeDec 18 2014We quantize spherically symmetric electrovacuum gravity. The algebra of Hamiltonian constraints can be made Abelian via a rescaling and linear combination with the diffeomorphism constraint. As a result the constraint algebra is a true Lie algebra. We ... More
The Moser-Trudinger-Onofri inequalityMar 20 2014May 21 2015This paper is devoted to results on the Moser-Trudinger-Onofri inequality, or Onofri inequality for brevity. In dimension two this inequality plays a role similar to the Sobolev inequality in higher dimensions. After justifying this statement by recovering ... More
On the stability of black holes with nonlinear electromagnetic fieldsFeb 12 2014The stability of three static and spherically symmetric black hole solutions with nonlinear electromagnetism as a source is investigated in three different ways. We show that the specific heat of all the solutions displays an infinite discontinuity with ... More
On the integration of fields and quanta in time dependent backgroundsDec 11 2013Field theories with global continuous symmetries may admit configurations in which time translation invariance is broken by the movement of homogeneous background fields evolving along the flat directions implied by the symmetries. In this context, the ... More
Time allocation in social networks: correlation between social structure and human communication dynamicsMay 16 2013Recent research has shown the deep impact of the dynamics of human interactions (or temporal social networks) on the spreading of information, opinion formation, etc. In general, the bursty nature of human interactions lowers the interaction between people ... More
Recent results from the Pierre Auger ObservatorySep 12 2008The main results from the Auger Observatory are described. A steepening of the spectrum is observed at the highest energies, supporting the expectation that above $4\times 10^{19}$ eV the cosmic ray energies are significantly degraded by interactions ... More
Spectral estimates on the sphereJan 07 2013Jun 16 2013In this article we establish optimal estimates for the first eigenvalue of Schr\"odinger operators on the d-dimensional unit sphere. These estimates depend on Lebsgue's norms of the potential, or of its inverse, and are equivalent to interpolation inequalities ... More
On the Relativistic Invariance of EntanglementSep 27 2011In this work we study the entanglement properties under a Lorentz boost of a pair of spin- 1 massive particles, with spin and momentum as the sole degrees of freedom of the system. Different cases for entanglement between spins and momenta are considered ... More
Massive star formation in Wolf-Rayet galaxies: IV b. Using empirical calibrations to compute the oxygen abundanceApr 29 2010We have performed a comprehensive multiwavelength analysis of a sample of 20 starburst galaxies that show a substantial population of very young massive stars, most of them classified as Wolf-Rayet (WR) galaxies. We have analysed optical/NIR colours, ... More
Astrophysical magnetic field reconstruction and spectroscopy with ultra high energy cosmic raysMay 28 2002The next generation of ultra high energy cosmic ray experiments will probably detect several dozens of events clustered around the direction towards each of the most powerful extragalactic sources. We develop a method which could make possible to reconstruct, ... More
Vacuum decay in quantum field theoryJun 08 2001We study the contribution to vacuum decay in field theory due to the interaction between the long and short-wavelength modes of the field. The field model considered consists of a scalar field of mass $M$ with a cubic term in the potential. The dynamics ... More
Master equation for quantum Brownian motion derived by stochastic methodsMar 12 2001The master equation for a linear open quantum system in a general environment is derived using a stochastic approach. This is an alternative derivation to that of Hu, Paz and Zhang, which was based on the direct computation of path integrals, or to that ... More
Cosmic ray photodisintegration and the knee of the spectrumNov 01 2000Jun 26 2001We explore in some detail the scenario proposed to explain the observed knee of the cosmic ray (CR) spectrum as due to the effects of photodisintegration of the CR nuclei by interactions with optical and soft UV photons in the source region. We show that ... More
Statistical physics of adaptive correlation of agents in a marketOct 27 2000Recent results and interpretations are presented for the thermal minority game, concentrating on deriving and justifying the fundamental stochastic differential equation for the microdynamics.
Continuous time dynamics of the Thermal Minority GameApr 17 2000Jul 11 2000We study the continuous time dynamics of the Thermal Minority Game. We find that the dynamical equations of the model reduce to a set of stochastic differential equations for an interacting disordered system with non-trivial random diffusion. This is ... More
Signatures of galactic magnetic lensing upon ultra high energy cosmic raysJan 06 2000We analyse several implications of lensing by the regular component of the galactic magnetic field upon the observed properties of ultra high energy cosmic rays. Magnetic fields deflect cosmic ray trajectories, causing flux (de)magnification, formation ... More