Results for "Anderson J. Pereira"

total 193448took 0.52s
Effects of a kinetic barrier on limited-mobility interface growth modelsFeb 08 2019Mar 27 2019The role played by a kinetic barrier originated by out-of-plane step edge diffusion, introduced in [Leal \textit{et al.}, \href{https://doi.org/10.1088/0953-8984/23/29/292201}{J. Phys. Condens. Matter \textbf{23}, 292201 (2011)}], is investigated in the ... More
Gravitational waves: a foundational reviewMay 03 2013May 27 2015The standard linear approach to the gravitational waves theory is critically reviewed. Contrary to the prevalent understanding, it is pointed out that this theory contains many conceptual and technical obscure issues that require further analysis.
Beta-decay properties of Zr and Mo neutron-rich isotopesJun 08 2010Gamow-Teller strength distributions, beta-decay half-lives, and beta-delayed neutron emission are investigated in neutron-rich Zr and Mo isotopes within a deformed quasiparticle random-phase approximation. The approach is based on a self-consistent Skyrme ... More
Lorentz Connections and GravitationOct 01 2012The different roles played by Lorentz connections in general relativity and in teleparallel gravity are reviewed. Some of the consequences of this difference are discussed.
Predicting Diabetes Disease Evolution Using Financial Records and Recurrent Neural NetworksNov 23 2018Managing patients with chronic diseases is a major and growing healthcare challenge in several countries. A chronic condition, such as diabetes, is an illness that lasts a long time and does not go away, and often leads to the patient's health gradually ... More
An analytical representation for the simplest of the diffusionsJan 15 2015Jan 21 2015An analytical representation for the spatial and temporal dynamics of the simplest of the diffusions -- Bronwian diffusion in an homogeneous slab geometry, with radial symmetry -- is presented. This representation is useful since it describes the time-resolved ... More
Comparison of multi-scale analysis models applied to zonal flow generation in ion-temperature-gradient mode turbulenceJan 14 2009During the past years the understanding of the multi-scale interaction problems have increased significantly. However, at present there exists a range of different analytical models for investigating multi-scale interactions and hardly any specific comparisons ... More
Is Physics Asking for a New Kinematics?May 16 2008Mar 13 2009It is discussed whether some of the consistency problems of present-day physics could be solved by replacing special relativity, whose underlying kinematics is ruled by the Poincare' group, by de Sitter relativity, with underlying kinematics ruled by ... More
Angular Momentum and Energy-Momentum Densities as Gauge CurrentsJan 23 2002Jul 11 2002If we replace the general spacetime group of diffeomorphisms by transformations taking place in the tangent space, general relativity can be interpreted as a gauge theory, and in particular as a gauge theory for the Lorentz group. In this context, it ... More
Completely reducible hypersurfaces in a pencilJan 10 2007Apr 09 2007We study completely reducible fibers of pencils of hypersurfaces on $\mathbb P^n$ and associated codimension one foliations of $\mathbb P^n$. Using methods from theory of foliations we obtain certain upper bounds for the number of these fibers as functions ... More
Entropy in locally-de Sitter spacetimesJun 23 2015Aug 06 2015As quotient spaces, Minkowski and de Sitter are fundamental spacetimes in the sense that they are known "a priori", independently of Einstein equation. They represent different non-gravitational backgrounds for the construction of physical theories. If ... More
Foliations invariant by rational mapsJul 08 2009Mar 15 2010We give a classification of pairs (F, f) where F is a holomorphic foliation on a projective surface and f is a non-invertible dominant rational map preserving F. We prove that both the map and the foliation are integrable in a suitable sense.
De Sitter Special Relativity: Effects on CosmologyDec 18 2008The main consequences of de Sitter Special Relativity to the Standard Cosmological Model of Physical Cosmology are examined. The cosmological constant Lambda appears, in this theory, as a manifestation of the proper conformal current, which must be added ... More
The Case for a Gravitational de Sitter Gauge TheoryOct 30 1996With the exception of gravitation, the known fundamental interactions of Nature are mediated by gauge fields. A comparison of the candidate groups for a gauge theory possibly describing gravitation favours the Poincar\'e group as the obvious choice. This ... More
Regge Calculus in Teleparallel GravityAug 14 2002In the context of the teleparallel equivalent of general relativity, the Weitzenbock manifold is considered as the limit of a suitable sequence of discrete lattices composed of an increasing number of smaller an smaller simplices, where the interior of ... More
Dark energy as a kinematic effectJun 05 2015Dec 03 2015We present a generalization of teleparallel gravity that is consistent with local spacetime kinematics regulated by the de Sitter group $SO(1,4)$. The mathematical structure of teleparallel gravity is shown to be given by a nonlinear Riemann-Cartan geometry ... More
Teleparallelism: A New Way to Think the Gravitational InteractionJun 11 2015At the time it celebrates one century of existence, general relativity---Einstein's theory for gravitation---is given a companion theory: the so-called teleparallel gravity, or teleparallelism for short. This new theory is fully equivalent to general ... More
de Sitter Relativity: a New Road to Quantum Gravity?Nov 14 2007Nov 12 2008The Poincare' group generalizes the Galilei group for high-velocity kinematics. The de Sitter group is assumed to go one step further, generalizing Poincare' as the group governing high-energy kinematics. In other words, ordinary special relativity is ... More
Radial Alignment of Cluster GalaxiesNov 25 2004May 25 2005We report the discovery of a statistically significant radial alignment of cluster galaxies in a sample of 85 X-ray selected clusters observed in the Sloan Digital Sky Survey. The tendency for alignment is a robust feature of our sample and does not vary ... More
Holographic Dark Energy and the Universe Expansion AccelerationFeb 24 2006By incorporating the holographic principle in a time-depending Lambda-term cosmology, new physical bounds on the arbitrary parameters of the model can be obtained. Considering then the dark energy as a purely geometric entity, for which no equation of ... More
How do magnetic microwires interact magnetostatically?Jun 07 2011The magnetostatic interaction between two ferromagnetic microwires is calculated as a function of their geometric parameters and compared with those measured through magnetic hysteresis loops of glass-coated amorphous Fe% $_{77.5}$Si$_{7.5}$B$_{15}$ microwires. ... More
Asymptotic safety and field parametrization dependence in the f(R) truncationMay 24 2018We study the dependence on field parametrization of the functional renormalization group equation in the $f(R)$ truncation for the effective average action. We perform a systematic analysis of the dependence of fixed points and critical exponents in polynomial ... More
Lattice Boltzmann method for bosons and fermions and the fourth order Hermite polynomial expansionNov 26 2013The Boltzmann equation with the Bhatnagar-Gross-Krook collision operator is considered for the Bose-Einstein and Fermi-Dirac equilibrium distribution functions. We show that the expansion of the microscopic velocity in terms of Hermite polynomials must ... More
Tuning the Fano factor of graphene via Fermi velocity modulationOct 30 2017In this work we investigate the influence of a Fermi velocity modulation on the Fano factor of periodic and quasi-periodic graphene superlattices. We consider the continuum model and use the transfer matrix method to solve the Dirac-like equation for ... More
Dirac wave transmission in Lévy disordered systemsFeb 26 2019We investigate the propagation of electronic waves described by the Dirac equation subject to a L\'evy-type disorder distribution. Our numerical calculations, based on the transfer matrix method, in a system with a distribution of potential barriers show ... More
An Information-Theoretic Measure of Uncertainty due to Quantum and Thermal FluctuationsApr 18 1993Apr 28 1993We study an information-theoretic measure of uncertainty for quantum systems. It is the Shannon information $I$ of the phase space probability distribution $\la z | \rho | z \ra $, where $|z \ra $ are coherent states, and $\rho$ is the density matrix. ... More
Symplectic matrices with predetermined left eigenvaluesJul 09 2009We prove that given four arbitrary quaternion numbers of norm 1 there always exists a $2\times 2$ symplectic matrix for which those numbers are left eigenvalues. The proof is constructive. An application to the LS category of Lie groups is given.
A topological approach to left eigenvalues of quaternionic matricesOct 10 2012It is known that a $2\times 2$ quaternionic matrix has one, two or an infinite number of left eigenvalues, but the available algebraic proofs are difficult to generalize to higher orders. In this paper a different point of view is adopted by computing ... More
Height functions on compact symmetric spacesJul 23 2013We consider height functions on symmetric spaces $M\cong G/K$ embedded in the associated matrix Lie group $G$. In particular we study the relationship between the critical sets of the height function on $G$ and its restriction to $M$. Also we prove that ... More
Diffusion and ballistic transport in one-dimensional quantum systemsJun 10 2009Nov 29 2010It has been conjectured that transport in integrable one-dimensional (1D) systems is necessarily ballistic. The large diffusive response seen experimentally in nearly ideal realizations of the S=1/2 1D Heisenberg model is therefore puzzling and has not ... More
Gamow-Teller response in deformed even and odd neutron-rich Zr and Mo isotopesMar 05 2014Beta-decay properties of neutron-rich Zr and Mo isotopes are investigated within a microscopic theoretical approach based on the proton-neutron quasiparticle random-phase approximation. The underlying mean field is described self-consistently from deformed ... More
Riemannian and Teleparallel Descriptions of the Scalar Field Gravitational InteractionJun 23 1997Aug 25 1997A comparative study between the metric and the teleparallel descriptions of gravitation is made for the case of a scalar field. In contrast to the current belief that only spin matter could detect the teleparallel geometry, scalar matter being able to ... More
Teleparallel origin of the Fierz picture for spin-2 particleDec 18 2002A new approach to the description of spin-2 particle in flat and curved spacetime is developed on the basis of the teleparallel gravity theory. We show that such an approach is in fact a true and natural framework for the Fierz representation proposed ... More
Some Remarks on the Neutrino Oscillation Phase in a Gravitational FieldFeb 18 2000Dec 06 2000The weak gravitational field expansion method to account for the gravitationally induced neutrino oscillation effect is critically examined. It is shown that the splitting of the neutrino phase into a ``kinematic'' and a ``gravitational'' phase is not ... More
Gravitational Lorentz Force and the Description of the Gravitational InteractionMar 21 1997Jun 23 1997In the context of a gauge theory for the translation group, we have obtained, for a spinless particle, a gravitational analog of the Lorentz force. Then, we have shown that this force equation can be rewritten in terms of magnitudes related to either ... More
An upper bound for the Lusternik-Schnirelmann category of the symplectic groupFeb 24 2012Mar 06 2012We prove that the LS category of the symplectic group $Sp(n)$ is bounded above by $\binom{n+1}{2}$. This is achieved by computing the number of critical levels of a height function.
CCDM model from quantum particle creation: constraints on dark matter massMar 14 2014Jun 16 2014In this work the results from the quantum process of matter creation have been used in order to constrain the mass of the dark matter particles in an accelerated Cold Dark Matter model (Creation Cold Dark Matter, CCDM). In order to take into account a ... More
Convolutions power of a characteristic functionApr 22 2012This paper deals with the convolution powers of the characteristic function of $[0,1], \chi_{[0,1]}$ and its function-derivatives. The importance that such convolution products have can be seen, for an instance, at \cite{DahmenLatour} where there is the ... More
Low temperature dynamics of nonlinear Luttinger liquidsOct 08 2014We generalize nonlinear Luttinger liquid theory to describe the dynamics of one-dimensional quantum critical systems at low temperatures. Analyzing density-matrix renormalization group results for the spin autocorrelation function in the XXZ chain we ... More
Conservation laws, integrability and transport in one-dimensional quantum systemsNov 05 2010In integrable one-dimensional quantum systems an infinite set of local conserved quantities exists which can prevent a current from decaying completely. For cases like the spin current in the XXZ model at zero magnetic field or the charge current in the ... More
de Sitter geodesics: reappraising the notion of motionOct 05 2011Mar 01 2012The de Sitter spacetime is transitive under a combination of translations and proper conformal transformations. Its usual family of geodesics, however, does not take into account this property. As a consequence, there are points in de Sitter spacetime ... More
Torsion and the Gravitational InteractionAug 30 2004Nov 04 2004By using a nonholonomous-frame formulation of the general covariance principle, seen as an active version of the strong equivalence principle, an analysis of the gravitational coupling prescription in the presence of curvature and torsion is made. The ... More
Kerr-Newman solution as a Dirac particleOct 10 2002Jan 19 2004For m^2 < a^2 + q^2, with m, a, and q respectively the source mass, angular momentum per unit mass, and electric charge, the Kerr--Newman (KN) solution of Einstein's equation reduces to a naked singularity of circular shape, enclosing a disk across which ... More
The quadratic spinor Lagrangian, axial torsion current, and generalizationsMar 13 2007We show that the Einstein-Hilbert, the Einstein-Palatini, and the Holst actions can be derived from the Quadratic Spinor Lagrangian (QSL), when the three classes of Dirac spinor fields, under Lounesto spinor field classification, are considered. To each ... More
Stability of foliations induced by rational mapsSep 26 2007We show that the singular holomorphic foliations induced by dominant quasi-homogeneous rational maps fill out irreducible components of the space $\mathscr F_q(r, d)$ of singular foliations of codimension $q$ and degree $d$ on the complex projective space ... More
Operad bimodules, and composition products on Andre-Quillen filtrations of algebrasFeb 22 2016If O is a reduced operad in symmetric spectra, an O-algebra I can be viewed as analogous to the augmentation ideal of an augmented algebra. Implicit in the literature on Topological Andre-Quillen homology is that such an I admits a canonical (and homotopically ... More
Characteristic functions and Hamilton-Cayley theorem for left eigenvalues of quaternionic matricesMay 04 2010May 07 2010We introduce the notion of characteristic function of a quaternionic matrix, whose roots are the left eigenvalues. We prove that for all $2\times 2$ matrices and for $3\times 3$ matrices having some zero entry outside the diagonal there is a characteristic ... More
Gauge Structure of Teleparallel GravityJun 14 2019During the conference "Teleparallel Universes in Salamanca", we became aware of a recent paper [M. Fontanini, E. Huguet, and M. Le Delliou, Phys. Rev. D 99 (2019) 064006] in which some criticisms on the interpretation of teleparallel gravity as a gauge ... More
Statistical properties of Charney-Hasegawa-Mima zonal flowsMar 30 2015A theoretical interpretation of numerically generated probability density functions (PDFs) of intermittent plasma transport events in unforced zonal flows is provided within the Charney-Hasegawa-Mima (CHM) model. The governing equation is solved numerically ... More
Quantum behavior of a charged particle in an axial magnetic fieldApr 30 2004Feb 02 2005We study some aspects of the quantum theory of a charged particle moving in a time-independent, uni-directional magnetic field. When the field is uniform, we make a few clarifying remarks on the use of angular momentum eigenstates and momentum eigenstates ... More
Some Implications of the Cosmological Constant to Fundamental PhysicsFeb 12 2007In the presence of a cosmological constant, ordinary Poincare' special relativity is no longer valid and must be replaced by a de Sitter special relativity, in which Minkowski space is replaced by a de Sitter spacetime. In consequence, the ordinary notions ... More
Time-Varying Cosmological Term: Emergence and Fate of a FRW UniverseDec 02 2003Apr 12 2005A time-varying cosmological "constant" Lambda is consistent with Einstein's equation, provided matter and/or radiation is created or destroyed to compensate for it. Supposing an empty primordial universe endowed with a very large cosmological term, matter ... More
de Sitter special relativityJun 28 2006Feb 08 2007A special relativity based on the de Sitter group is introduced, which is the theory that might hold up in the presence of a non-vanishing cosmological constant. Like ordinary special relativity, it retains the quotient character of spacetime, and a notion ... More
Application of Monte Carlo Algorithms to the Bayesian Analysis of the Cosmic Microwave BackgroundSep 26 2002Power spectrum estimation and evaluation of associated errors in the presence of incomplete sky coverage; non-homogeneous, correlated instrumental noise; and foreground emission is a problem of central importance for the extraction of cosmological information ... More
Asymmetric exclusion model with impuritiesMay 20 2010An integrable asymmetric exclusion process with impurities is formulated. The model displays the full spectrum of the stochastic asymmetric XXZ chain plus new levels. We derive the Bethe equations and calculate the spectral gap for the totally asymmetric ... More
A theory of non-local linear drift wave transportMar 15 2011Jul 13 2011Transport events in turbulent tokamak plasmas often exhibit non-local or non-diffusive action at a distance features that so far have eluded a conclusive theoretical description. In this paper a theory of non-local transport is investigated through a ... More
Astrometry and photometry with HST WFC3. II. Improved geometric-distortion corrections for 10 filters of the UVIS channelFeb 25 2011We present an improved geometric-distortion solution for the Hubble Space Telescope UVIS channel of Wide Field Camera 3 for ten broad-band filters. The solution is made up of three parts: (1) a 3rd-order polynomial to deal with the general optical distortion, ... More
NAK for Ext and Ascent of module structuresJan 14 2012May 14 2012We investigate the interplay between properties of Ext modules and ascent of module structures along local ring homomorphisms. Specifically, let f: (R,m,k) -> (S,mS,k) be a flat local ring homomorphism. We show that if M is a finitely generated R-module ... More
Surface and Bulk Effects of K in Cu$_{1-x}$K$_x$In$_{1-y}$Ga$_y$Se$_2$ Solar CellsMar 18 2017Two strategies for enhancing photovoltaic (PV) performance in chalcopyrite solar cells were investigated: Cu1-xKxIn1-yGaySe2 absorbers with low K content (K/(K+Cu), or x ~ 0.07) distributed throughout the bulk, and CuIn1-yGaySe2 absorbers with KIn1-yGaySe2 ... More
Chameleon effect and the Pioneer anomalyApr 12 2012The possibility that the apparent anomalous acceleration of the Pioneer 10 and 11 spacecraft may be due, at least in part, to a chameleon field effect is examined. A small spacecraft, with no thin shell, can have a more pronounced anomalous acceleration ... More
Generic Connectivity-Based CGRA Mapping via Integer Linear ProgrammingJan 30 2019Apr 30 2019Coarse-grained reconfigurable architectures (CGRAs) are programmable logic devices with large coarse-grained ALU-like logic blocks, and multi-bit datapath-style routing. CGRAs often have relatively restricted data routing networks, so they attract CAD ... More
Multi-level Monte Carlo for continuous time Markov chains, with applications in biochemical kineticsJul 12 2011Nov 21 2011We show how to extend a recently proposed multi-level Monte Carlo approach to the continuous time Markov chain setting, thereby greatly lowering the computational complexity needed to compute expected values of functions of the state of the system to ... More
Asymmetric exclusion model with several kinds of impuritiesMay 02 2012We formulate a new integrable asymmetric exclusion process with $N-1=0,1,2,...$ kinds of impurities and with hierarchically ordered dynamics. The model we proposed displays the full spectrum of the simple asymmetric exclusion model plus new levels. The ... More
Localization for Uniform Algebras Generated by Real-Analytic FunctionsSep 27 2015Dec 24 2016It is shown that if $A$ is a uniform algebra generated by real-analytic functions on a suitable compact subset $K$ of a real-analytic variety such that the maximal ideal space of $A$ is $K$, and every continuous function on $K$ is locally a uniform limit ... More
A Peak Point Theorem for Uniform Algebras on Real-Analytic VarietiesJul 20 2015It was once conjectured that if $A$ is a uniform algebra on its maximal ideal space $X$, and if each point of $X$ is a peak point for $A$, then $A = C(X)$. This peak-point conjecture was disproved by Brian Cole in 1968. Here we establish a peak-point ... More
Probing nonlinear electrodynamics in slowly rotating spacetimes through neutrino astrophysicsJan 02 2017Huge electromagnetic fields are known to be present during the late stages of the dynamics of supernovae. Thus, when dealing with electrodynamics in this context, the possibility may arise to probe nonlinear theories (generalizations of the Maxwellian ... More
A simple setup for neutron tomography at the Portuguese Nuclear Research ReactorMay 15 2012A simple setup for neutron radiography and tomography was recently installed at the Portuguese Research Reactor. The objective of this work was to determine the operational characteristics of the installed setup, namely the irradiation time to obtain ... More
Boron and nitrogen doping in graphene antidot latticesJul 27 2016Bottom-up fabrication of graphene antidot lattices (GALs) has previously yielded atomically precise structures with sub-nanometer periodicity. Focusing on this type of experimentally realized GAL, we perform density functional theory calculations on the ... More
Nonextensive effects on the phase structure of QHDJun 12 2009We investigate nonextensive effects on phase transition in nuclear matter in the context Walecka many-body field theory. Changes in the general behavior are observed when the results calculated for the nuclear matter at vanishing baryon density are compared ... More
Non-gaussian statistics and the relativistic nuclear equation of stateFeb 13 2009We investigate possible effects of quantum power-law statistical mechanics on the relativistic nuclear equation of state in the context of the Walecka quantum hadrodynamics theory. By considering the Kaniadakis non-Gaussian statistics, characterized by ... More
Exactly conserved quasilocal operators for the XXZ spin chainJun 09 2014Sep 30 2014We extend T. Prosen's construction of quasilocal conserved quantities for the XXZ model [Phys. Rev. Lett. 106, 217206 (2011)] to the case of periodic boundary conditions. These quasilocal operators stem from a two-parameter transfer matrix which employs ... More
de Sitter invariant special relativity and galaxy rotation curvesJun 17 2017Jun 12 2019Owing to the existence of an invariant length at the Planck scale, Einstein special relativity breaks down at that scale. A possible solution to this problem is arguably to replace the Poincar\'e invariant Einstein special relativity by a de Sitter invariant ... More
Testing the Newton second law in the regime of small accelerationsFeb 15 2010It has been pointed out that the Newtonian second law can be tested in the very small acceleration regime by using the combined movement of the Earth and Sun around the Galactic center of mass. It has been shown that there are only two brief intervals ... More
Gravity and the Quantum: Are they Reconcilable?Sep 14 2005General relativity and quantum mechanics are conflicting theories. The seeds of discord are the fundamental principles on which these theories are grounded. General relativity, on one hand, is based on the equivalence principle, whose strong version establishes ... More
Gravitation without the equivalence principleApr 29 2003Aug 31 2003In the general relativistic description of gravitation, geometry replaces the concept of force. This is possible because of the universal character of free fall, and would break down in its absence. On the other hand, the teleparallel version of general ... More
Conformal and gauge invariant spin-2 field equationsMay 07 2013Using an approach based on the Casimir operators of the de Sitter group, the conformal invariant equations for a fundamental spin-2 field are obtained, and their consistency discussed. It is shown that, only when the spin-2 field is interpreted as a 1-form ... More
Landau levels and oscillator strength in a biased bilayer of grapheneAug 06 2007We obtain analytical expressions for the eigenstates and the Landau level spectrum of biased graphene bilayers in a magnetic field. The calculations are performed in the context of a four-band continuum model and generalize previous approximate results. ... More
Graphene-based resonant-tunneling strucuresFeb 26 2007Resonant electronic transmission through graphene-based double barriers (wells) is studied as a function of the incident wave vector, the widths and heights (depths) of the barriers (wells), and the separation between them. Resonant features in the transmission ... More
The Korteweg-de Vries Hierarchy and Long Water-WavesJun 17 1994By using the multiple scale method with the simultaneous introduction of multiple times, we study the propagation of long surface-waves in a shallow inviscid fluid. As a consequence of the requirements of scale invariance and absence of secular terms ... More
The Orbital Period of the Accreting Pulsar GX1+4Oct 04 1999We report strong evidence for a ~304-day periodicity in the spin history of the accretion-powered pulsar GX1+4 that is most probably associated with the orbital period of the system. We have used data from the Burst and Transient Source Experiment on ... More
Relative singular value decomposition and applications to LS-categoryApr 22 2019Let $Sp(n)$ be the symplectic group of quaternionic $(n\times n)$-matrices. For any $1\leq k\leq n$, an element $A$ of $Sp(n)$ can be decomposed in $A= \begin{bmatrix} \alpha&T\cr \beta&P \end{bmatrix}$ with $P$ a $(k\times k)$-matrix. In this work, starting ... More
Bounding Game Temperature Using Confusion IntervalsAug 22 2019For combinatorial games, temperature is a measure of the volatility, that is, by how much the advantage can change. Typically, the temperature has been measured for individual positions within specific games. In this paper, we give the first general upper ... More
Energy in an Expanding Universe in the Teleparallel GeometryFeb 20 2007Dec 07 2009The main purpose of this paper is to explicitly verify the consistency of the energy-momentum and angular momentum tensor of the gravitational field established in the Hamiltonian structure of the Teleparallel Equivalent of General Relativity (TEGR). ... More
Current flow in biased bilayer graphene: the role of sublatticesAug 21 2014We investigate here how the current flows over a bilayer graphene in the presence of an external electric field perpendicularly applied (biased bilayer). Charge density polarization between layers in these systems is known to create a layer pseudospin, ... More
On the energy transported by exact plane gravitational-wave solutionsSep 24 2009The energy and momentum transported by exact plane gravitational-wave solutions of Einstein equations are computed using the teleparallel equivalent formulation of Einstein's theory. It is shown that these waves transport neither energy nor momentum. ... More
The Nonlinear Essence of Gravitational WavesSep 11 2007A critical review of gravitational wave theory is made. It is pointed out that the usual linear approach to the gravitational wave theory is neither conceptually consistent nor mathematically justified. Relying upon that analysis it is then argued that ... More
Magnetic interface states in graphene-based quantum wiresOct 09 2006The electronic states of a finite-width graphene sheet in the presence of an electrostatic confining potential and a perpendicular magnetic field are investigated. The confining potential shifts the Landau levels inside the well and creates current-carrying ... More
Torsion as Alternative to Curvature in the Description of GravitationDec 08 2004The general covariance principle, seen as an active version of the principle of equivalence, is used to study the gravitational coupling prescription in the presence of curvature and torsion. It is concluded that the coupling prescription determined by ... More
Torsion and Gravitation: A new viewMar 16 2004According to the teleparallel equivalent of general relativity, curvature and torsion are two equivalent ways of describing the same gravitational field. Despite equivalent, however, they act differently: whereas curvature yields a geometric description, ... More
Axial-Vector Torsion and the Teleparallel Kerr SpacetimeFeb 14 2001In the context of the teleparallel equivalent of general relativity, we obtain the tetrad and the torsion fields of the stationary axisymmetric Kerr spacetime. It is shown that, in the slow rotation and weak field approximations, the axial-vector torsion ... More
Gravitomagnetic Moments of the Fundamental FieldsApr 17 1998Sep 15 1998The quadratic form of the Dirac equation in a Riemann spacetime yields a gravitational gyromagnetic ratio \kappa_S = 2 for the interaction of a Dirac spinor with curvature. A gravitational gyromagnetic ratio \kappa_S = 1 is also found for the interaction ... More
Gravitation and Duality SymmetryJan 12 2005May 16 2005By generalizing the Hodge dual operator to the case of soldered bundles, and working in the context of the teleparallel equivalent of general relativity, an analysis of the duality symmetry in gravitation is performed. Although the basic conclusion is ... More
General Relativity as a Genuine Connection TheoryDec 07 2004The Palatini formulation is used to develop a genuine connection theory for general relativity, in which the gravitational field is represented by a Lorentz-valued spin connection. The existence of a tetrad field, given by the Fock-Ivanenko covariant ... More
Evidence for a 304-day Orbital Period for GX 1+4Dec 27 1999In this paper we report strong evidence for a ~304-day periodicity in the spin history of the accretion-powered pulsar GX 1+4 that is very likely to be a signature of the orbital period of the system. Using BATSE public-domain data, we show a highly-significant ... More
Dipole-exchange spin waves in Fibonacci magnetic multilayersMar 29 2005A microscopic model is employed to calculate the spectrum of spin waves in quasiperiodic magnetic multilayers in the dipole-exchange regime. Results are presented for structures in which thin ferromagnetic films are separated by non-magnetic spacers following ... More
A new approach on the stability analysis in ELKO cosmologyJul 12 2014Jan 05 2015In this work it has been developed a new approach to study the stability of a system composed by an ELKO field interacting with dark matter, which could give some contribution in order to alleviate the cosmic coincidence problem. It is assumed that the ... More
Satellite Test of the Equivalence Principle as a Probe of Modified Newtonian DynamicsJul 23 2016The proposed Satellite Test of the Equivalence Principle (STEP) will detect possible violations of the Weak Equivalence Principle by measuring relative accelerations between test masses of different composition with a precision of one part in $10^{18}$. ... More
The theory of quantum levitatorsMar 03 2011Jun 29 2011We develop a unified theory for clocks and gravimeters using the interferences of multiple atomic waves put in levitation by traveling light pulses. Inspired by optical methods, we exhibit a propagation invariant, which enables to derive analytically ... More
A Color Quantization Optimization Approach for Image Representation LearningNov 18 2017Nov 23 2017Over the last two decades, hand-crafted feature extractors have been used in order to compose image representations. Recently, data-driven feature learning have been explored as a way of producing more representative visual features. In this work, we ... More
Spin and Anholonomy in General RelativityFeb 04 2004Feb 05 2004In the general case, torsion couples to the spin current of the Dirac field. In General Relativity, the apparent torsion field to which the spin current of the Dirac field couples is a mere manifestation of the tetrad anholonomy. Seen from the tetrad ... More