Results for "Anderson J. Pereira"

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Effects of a kinetic barrier on limited-mobility interface growth modelsFeb 08 2019Feb 13 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.
In Search of the Spacetime TorsionApr 09 2007Whether torsion plays or not a role in the description of the gravitational interaction is a problem that can only be solved by experiment. This is, however, a difficult task: since there are different possible interpretations for torsion, there is no ... More
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
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.
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
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
Teleparallelism: A New Insight Into GravityFeb 27 2013Aug 25 2014Teleparallel gravity, a gauge theory for the translation group, turns up as fully equivalent to Einstein's general relativity. In spite of this equivalence, it provides a whole new insight into gravitation. It breaks several paradigms related to the geometric ... 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
Spin Connection and Renormalization of Teleparallel ActionApr 28 2015Oct 05 2015In general relativity, inertia and gravitation are both included in the Levi-Civita connection. As a consequence, the gravitational action, as well as the corresponding energy-momentum density, are in general contaminated by spurious contributions coming ... More
Gravitation and the Local Symmetry Group of SpacetimeJan 17 2002Feb 28 2002According to general relativity, the interaction of a matter field with gravitation requires the simultaneous introduction of a tetrad field, which is a field related to translations, and a spin connection, which is a field assuming values in the Lie ... More
A Second Poincare' GroupSep 21 1998Solutions of the sourceless Einstein's equation with weak and strong cosmological constants are discussed by using In\"on\"u-Wigner contractions of the de Sitter groups and spaces. The more usual case corresponds to a weak cosmological-constant limit, ... 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
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
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
Gravitation: in search of the missing torsionJan 27 2008A linear Lorentz connection has always two fundamental derived characteristics: curvature and torsion. The latter is assumed to vanish in general relativity. Three gravitational models involving non-vanishing torsion are examined: teleparallel gravity, ... 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
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
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
On the multiplicity of supernovae within host galaxiesDec 17 2012We investigate the nature of multiple supernova hosting galaxies, and the types of events which they produce. Using all known historical supernovae, we split host galaxies into samples containing single or multiple events. These samples are then characterised ... 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
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
Exploring Higher-Order Gravitational WavesApr 29 2015In addition to the usual linear gravitational waves in transverse-traceless coordinates, higher-order gravitational field equations, as well as their corresponding solutions, are explicitly obtained. It is found that higher-order waves do not represent ... More
Hodge Dual for Soldered BundlesNov 13 2008In order to account for all possible contractions allowed by the presence of the solder form, a generalized Hodge dual is defined for the case of soldered bundles. Although for curvature the generalized dual coincides with the usual one, for torsion it ... More
Spacetime: Arena or Reality?Oct 01 2007For small values of the mass (in relation to the angular momentum and electric charge), the Kerr-Newman (KN) solution of Einstein equation reduces to a naked singularity of circular shape. By considering the Hawking and Ellis extended interpretation of ... More
Some Remarks on the Coupling Prescription of Teleparallel GravityDec 21 2003Oct 18 2004By using a nonholonomic moving frame version of the general covariance principle, an active version of the equivalence principle, an analysis of the gravitational coupling prescription of teleparallel gravity is made. It is shown that the coupling prescription ... More
ADDENDUM on the mass neutrino oscillation in a gravitational fieldMay 08 2002In the article {\it Gen. Rel. Grav.} {\bf 32}, 1633 (2000), by J. G. Pereira and C. M. Zhang, the special relativity energy-momentum tensor was used to discuss the neutrino phase-splitting in a weak gravitational field. However, it would be more appropriate ... More
Torsion Gravity: a ReappraisalJan 07 2005The role played by torsion in gravitation is critically reviewed. After a description of the problems and controversies involving the physics of torsion, a comprehensive presentation of the teleparallel equivalent of general relativity is made. According ... More
Metric-affine approach to teleparallel gravityDec 19 2002The teleparallel gravity theory, treated physically as a gauge theory of translations, naturally represents a particular case of the most general gauge-theoretic model based on the general affine group of spacetime. On the other hand, geometrically, the ... More
Cosmological Constant and the Speed of LightJun 28 2000By exploring the relationship between the propagation of electromagnetic waves in a gravitational field and the light propagation in a refractive medium, it is shown that, in the presence of a positive cosmological constant, the velocity of light will ... More
Torsion and the Electromagnetic FieldAug 21 1997Jan 11 1999In the framework of the teleparallel equivalent of general relativity, we study the dynamics of a gravitationally coupled electromagnetic field. It is shown that the electromagnetic field is able not only to couple to torsion, but also, through its energy-momentum ... More
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
Riccati-Ermakov systems and explicit solutions for variable coefficient reaction-diffusion equationsAug 21 2017Oct 23 2017We present several families of nonlinear reaction diffusion equations with variable coefficients including Fisher-KPP and Burgers type equations. Special exact solutions such as traveling wave, rational, triangular wave and N-wave type solutions are shown. ... 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.
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
Uneven rock-paper-scissors models: patterns and coexistenceApr 15 2019We study a class of the stochastic May-Leonard models, with three species dominating each other in a cyclic nonhierarchical way, according to the rock-paper-scissors game. We introduce an unevenness in the system, by considering that one the species is ... 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
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
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
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
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
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
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
Hard thermal loops in static external fieldsFeb 04 2009We study, in the imaginary-time formalism, the high temperature behavior of n-point thermal loops in static Yang-Mills and gravitational fields. We show that in this regime, any hard thermal loop gives the same leading contribution as the one obtained ... 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
Tidal Torquing of Elliptical Galaxies in Cluster EnvironmentsSep 21 2010Observational studies of galaxy isophotal shapes have shown that galaxy orientations are anisotropic: a galaxy's long axis tends to be oriented toward the center of its host. This radial alignment is seen across a wide range of scales, from galaxies in ... More
Electrostatic theory for imaging experiments on local charges in quantum Hall systemsFeb 12 2005We use a simple electrostatic treatment to model recent experiments on quantum Hall systems, in which charging of localised states by addition of integer or fractionally-charged quasiparticles is observed. Treating the localised state as a compressible ... More
Landau levels of single layer and bilayer phosphoreneApr 09 2015In this work we introduce a low-energy Hamiltonian for single layer and bilayer black phosphorus that describes the electronic states at the vicinity of the gamma point. The model is based on a recently proposed tight-binding description for electron ... More
Lessons of spin and torsion: Reply to ``Consistent coupling to Dirac fields in teleparallelism"Jun 04 2004In reply to the criticism made by Mielke in the pereceding Comment [Phys. Rev. D69 (2004) 128501] on our recent paper, we once again explicitly demonstrate the inconsistency of the coupling of a Dirac field to gravitation in the teleparallel equivalent ... More
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
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.
Left eigenvalues of $2\times 2$ symplectic matricesDec 11 2008We obtain a complete characterization of the $2\times 2$ symplectic matrices having an infinite number of left eigenvalues. Previously, we give a new proof of a result from Huang and So about the number of eigenvalues of a quaternionic matrix. This is ... 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
Optimal bispectrum constraints on single-field models of inflationMar 13 2014We use WMAP 9-year bispectrum data to constrain the free parameters of an 'effective field theory' describing fluctuations in single-field inflation. The Lagrangian of the theory contains a finite number of operators associated with unknown mass scales. ... More
Phonon-Based Position Determination in SuperCDMS iZIP DetectorsMay 16 2014SuperCDMS is currently operating a 10-kg array of cryogenic germanium detectors in the Soudan underground laboratory to search for weakly interacting massive particles, a leading dark matter candidate. These detectors, known as iZIPs, measure ionization ... 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
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
Lower Schwarz-Pick estimates and angular derivativesAug 22 2006Aug 28 2006The well-known Schwarz-Pick lemma states that any analytic mapping $\phi$ of the unit disk $U$ into itself satisfies the inequality $$|\phi'(z)|\leq \frac{1-|\phi(z)|^2}{1-|z|^2}, \quad z\in U.$$ This estimate remains the same if we restrict ourselves ... 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
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
Generic Connectivity-Based CGRA Mapping via Integer Linear ProgrammingJan 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
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
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
Simple learning models can illuminate biased results from choice titration experimentsJun 15 2013Jun 22 2013The choice titration procedure presents a subject with a repeated choice between a standard option that always provides the same reward and an adjusting option for which the reward schedule is adjusted based on the subjects previous choices. The procedure ... 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
Cosmological Term and Fundamental PhysicsMay 19 2004A nonvanishing cosmological term in Einstein's equations implies a nonvanishing spacetime curvature even in absence of any kind of matter. It would, in consequence, affect many of the underlying kinematic tenets of physical theory. The usual commutative ... 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
Transient and quasi-stationary dissipative effects in the fission flux across the barrier in 1 A GeV 238U on deuterium reactionsNov 18 2005Isotopic cross sections of all projectile residues with Z above 23 produced in collisions induced by 238U at 1 A GeV on deuterium have been measured. The isotopic distributions reflect the role of evaporation and fission in the formation process of these ... More
A Singular Conformal SpacetimeMar 24 2004Jun 22 2005The infinite cosmological "constant" limit of the de Sitter solutions to Einstein's equation is studied. The corresponding spacetime is a singular, four-dimensional cone-space, transitive under proper conformal transformations, which constitutes a new ... 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
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
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
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
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
de Sitter transitivity, conformal transformations and conservation lawsDec 11 2013Minkowski spacetime is transitive under ordinary translations, a transformation that do not have matrix representations. The de Sitter spacetime, on the other hand, is transitive under a combination of translations and proper conformal transformations, ... 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
Consistent Gravitationally-Coupled Spin-2 Field TheoryJan 19 2010May 05 2010Inspired by the translational gauge structure of teleparallel gravity, the theory for a fundamental massless spin-2 field is constructed. Accordingly, instead of being represented by a symmetric second-rank tensor, the fundamental spin-2 field is assumed ... More
Doing without the Equivalence PrincipleOct 08 2004In Einstein's general relativity, geometry replaces the concept of force in the description of the gravitation interaction. Such an approach rests on the universality of free-fall--the weak equivalence principle--and would break down without it. On the ... More
Tunable quantum dots in bilayer grapheneMar 07 2007We demonstrate theoretically that quantum dots in bilayers of graphene can be realized. A position-dependent doping breaks the equivalence between the upper and lower layer and lifts the degeneracy of the positive and negative momentum states of the dot. ... More
Selected Topics in Teleparallel GravityDec 01 2003Teleparallel gravity can be seen as a gauge theory for the translation group. As such, its fundamental field is neither the tetrad nor the metric, but a gauge potential assuming values in the Lie algebra of the translation group. This gauge character ... More
Kinematics of a Spacetime with an Infinite Cosmological ConstantMay 18 2001Dec 02 2002A solution of the sourceless Einstein's equation with an infinite value for the cosmological constant \Lambda is discussed by using Inonu-Wigner contractions of the de Sitter groups and spaces. When \Lambda --> infinity, spacetime becomes a four-dimensional ... More