Results for "M. A. de Souza"

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Electromagnetic wave propagation inside a material medium: an effective geometry interpretationFeb 06 2001May 07 2001We present a method developed to deal with electromagnetic wave propagation inside a material medium that reacts, in general, non-linearly to the field strength. We work in the context of Maxwell' s theory in the low frequency limit and obtain a geometrical ... More
The Dyer-Roeder relation in a universe with particle productionSep 27 2003Jun 30 2004We have obtained analytical exact solutions of the Dyer-Roeder equation in a cosmological model where creation of particles occurs at the expenses of the gravitational field. We discussed the influences of inhomogeneities in the path of a light beam on ... More
Gravity from Discrete Interactions, a laboratory of ideas for field theoryDec 06 2012The observed accelerated expansion of the universe is an indication that somehow, in some conditions, gravity may become a repulsive interaction. The very concept of discrete interactions, compatible with General Relativity as an effective theory of averaged ... More
Discrete scalar fields and general relativityJun 30 2000Oct 03 2000The physical meaning, the properties and the consequences of a discrete scalar field are discussed; limits for a continuous mathematical description of fundamental physics is a natural outcome of discrete fields with discrete interactions. The discrete ... More
Classical Electrodynamics and the Quantum Nature of LightOct 05 1996A review of old inconsistencies of Classical Electrodynamics (CED) and of some new ideas that solve them is presented. Problems with causality violating solutions of the wave equation and of the electron equation of motion, and problems with the non-integrable ... More
The Lorentz-Dirac Equation and the Physical Meaning of the Maxwell's FieldsOct 21 1995Nov 21 1995Classical Electrodynamics is not a consistent theory because of its field inadequate behaviour in the vicinity of their sources. Its problems with the electron equation of motion and with non-integrable singularity of the electron self field and of its ... More
Discrete scalar field and general relativityDec 26 2001What is the nature - continuous or discrete - of matter and of its fundamental interactions? The physical meaning, the properties and the consequences of a discrete scalar field are discussed; limits for the validity of a mathematical description of fundamental ... More
Discrete Classical Electromagnetic FieldsOct 28 1997The classical electromagnetic field of a spinless point electron is described in a formalism with extended causality by discrete finite transverse point-vector fields with discrete and localized point interactions. These fields are taken as a classical ... More
Classical Fields and the Quantum ConceptOct 18 1996Nov 03 1996We do a critical review of the Faraday-Maxwell concept of classical field and of its quantization process. With the hindsight knowledge of the essentially quantum character of the interactions, we use a naive classical model of field, based on exchange ... More
The Lorents-Dirac equation and the structure of spacetimeMay 26 1995Jan 04 1996A new interpretation of the causality implementation in the Lienard-Wiechert solution raises new doubts against the validity of the Lorentz-Dirac equation and the limits of validity of the Minkowski structure of spacetime.
Gravity and Antigravity with Discrete Interactions: Alternatives I and IINov 16 2001Questioning the experimental basis of continuous descriptions of fundamental interactions we discuss classical gravity as an effective continuous first-order approximation of a discrete interaction. The sub-dominant contributions produce a residual interaction ... More
Discrete interactions and the Pioneer anomalous acceleration: Alternative IIJun 14 2001The dominant contributions from a discrete gravitational interaction produce the standard potential as an effective continuous field. The sub-dominant contributions are, in a first approximation, linear on $n$, the accumulated number of (discrete) interaction ... More
Conformally symmetric massive discrete fieldsJun 29 2000Mar 23 2001Conformal symmetry is taken as an attribute of theories of massless fields in manifolds with specific dimensionalities. This paper shows that this is not an absolute truth; it is a consequence of the mathematical representation used for the physical interactions. ... More
A new approach to gauge fieldsNov 16 1998A discrete field formalism exposes the physical meaning and the origins of gauge fields and of their symmetries and singularities.
Dynamics and causality constraints in field theoryAug 18 1997We discuss the physical meaning and the geometric interpretation of causality implementation in classical field theories. Causality is normally implemented through kinematical constraints on fields but we show that in a zero-distance limit they also carry ... More
Discrete fields and the Pioneer anomalous accelerationJun 14 2001The dominant contributions from a discrete gravitational interaction produce the standard potential as an effective continuous field. The sub-dominant contributions are, in a first approximation, linear on n, the accumulated number of (discrete) interaction ... More
Discrete fields, general relativity, other possible implications and experimental evidencesMar 26 2001The physical meaning, the properties and the consequences of a discrete scalar field are discussed; limits for the validity of a mathematical description of fundamental physics in terms of continuous fields are a natural outcome of discrete fields with ... More
Dynamics and causality constraintsJun 27 2000Sep 25 2000The physical meaning and the geometrical interpretation of causality implementation in classical field theories are discussed. Local causality are kinematical constraints dynamically implemented via solutions of the field equations, but in a limit of ... More
Gauge fields in a discrete approachSep 21 1999A discrete field formalism exposes the physical meaning and origins of gauge fields, their symmetries and singularities. They represent a lack of a stricter field-source coherence.
Causality and Self-consistency in Classical ElectrodynamicsMay 02 1996May 26 1996We present a pedagogical review of old inconsistencies of Classical Electrodynamics and of some new ideas that solve them. Problems with the electron equation of motion and with the non-integrable singularity of its self-field energy tensor are well known. ... More
Discrete fields on the lightconeAug 11 1997We introduce a classical field theory based on a concept of extended causality that mimics the causality of a point-particle Classical Mechanics by imposing constraints that are equivalent to a particle initial position and velocity. It results on a description ... More
Electrodynamics Classical InconsistenciesNov 21 1995Nov 23 1995The problems of Classical Electrodynamics with the electron equation of motion and with non-integrable singularity of its self-field stress tensor are well known. They are consequences, we show, of neglecting terms that are null off the charge world line ... More
Discrete gauge fieldsNov 29 1999The use of proper time as a tool for causality implementation in field theory is clarified and extended to allow a manifestly covariant definition of discrete fields proper to be applied in field theory and quantum mechanics. It implies on a constraint ... More
Mapping deformed hyperbolic potentials into nondeformed onesJan 18 2005In this work we introduce a mapping between the so called deformed hyperbolic potentials, which are presenting a continuous interest in the last few years, and the corresponding nondeformed ones. As a consequence, we conclude that these deformed potentials ... More
Strong-Weak Coupling Duality in Quantum MechanicsSep 18 1996We present a strong-weak coupling duality for quantum mechanical potentials. Similarly to what happens in quantum field theory, it relates two problems with inverse couplings, leading to a mapping of the strong coupling regime into the weak one, giving ... More
Discrete-to-continuum transitions and mathematical generalizations in the classical harmonic oscillatorMay 13 2003Sep 22 2003Discrete interaction models for the classical harmonic oscillator are used for introducing new mathematical generalizations in the usual continuous formalism. The inverted harmonic potential and generalized discrete hyperbolic and trigonometric functions ... More
Quantum propagator for some classes of three-dimensional three-body systemsMay 18 2007In this work we solve exactly a class of three-body propagators for the most general quadratic interactions in the coordinates, for arbitrary masses and couplings. This is done both for the constant as the time-dependent couplings and masses, by using ... More
Probing the Antisymmetric Fano Interference Assisted by a Majorana FermionAug 03 2014Nov 08 2014As the Fano effect is an interference phenomenon where tunneling paths compete for the electronic transport, it becomes a probe to catch fingerprints of Majorana fermions lying on condensed matter systems. In this work we benefit of this mechanism by ... More
Information-Entropic Measure of Energy-Degenerate Kinks in Two-Field ModelsAug 29 2014We investigate the existence and properties of kink-like solitons in a class of models with two interacting scalar fields. In particular, we focus on models that display both double and single-kink solutions, treatable analytically using the Bogomol'nyi--Prasad--Sommerfield ... More
Two field BPS solutions for generalized Lorentz breaking modelsMay 18 2007In this work we present nonlinear models in two-dimensional space-time of two interacting scalar fields in the Lorentz and CPT violating scenarios. We discuss the soliton solutions for these models as well as the question of stability for them. This is ... More
Multipartite Quantum EraserOct 27 2012We study the dynamical entanglement distribution in a multipartite system. The initial state is a maximally entangled two level atom with a single photon field. Next a sequence of atoms are sent, one at the time, and interact with the field. We show that ... More
Generalizing the Soldering procedureJul 16 2006We start this work by revisiting the problem of the soldering of two chiral Schwinger models of opposite chiralities. We verify that, in contrast with what one can conclude from the soldering literature, the usual sum of these models is, in fact, gauge ... More
A mapping function approach applied to some classes of nonlinear equationsFeb 24 2010In this work, we study some models of scalar fields in 1+1 dimensions with non-linear self-interactions. Here, we show how it is possible to extend the solutions recently reported in the literature for some classes of nonlinear equations like the nonlinear ... More
The Einstein specific heat model for finite systemsJan 13 2016The theoretical model proposed by Einstein to describe the phononic specific heat of solids as a function of temperature consists the very first application of the concept of energy quantization to describe the physical properties of a real system. Its ... More
Halpha spectropolarimetry of the B[e] supergiant GG CarinaeOct 29 2009Oct 30 2009Aims. We study the geometry of the circumstellar environment of the B[e] supergiant star GG Car. Methods. We present observations acquired using the IAGPOL imaging polarimeter in combination with the Eucalyptus-IFU spectrograph to obtain spectropolarimetric ... More
The Hamming and Golay Number-Theoretic TransformsJun 25 2018Sep 25 2018New number-theoretic transforms are derived from known linear block codes over finite fields. In particular, two new such transforms are built from perfect codes, namely the \textit {Hamming number-theoretic transform} and the \textit {Golay number-theoretic ... More
Effect of Inter-Adatoms Correlations on the Local Density of States of GrapheneMay 21 2014Nov 24 2014We discuss theoretically the local density of states (LDOS) of a graphene sheet hosting two distant adatoms located at the center of the hexagonal cells. By putting laterally a Scanning Tunneling Microscope (STM) tip over a carbon atom, two remarkable ... More
A complete set of eigenstates for position-dependent massive particles in a Morse-like scenarioMay 29 2015Oct 13 2016In this work we analyze a system consisting in two-dimensional position-dependent massive particles in the presence of a Morse-like potential in two spatial dimensions. We obtain the exact wavefunctions and energies for a complete set of eigenstates for ... More
The Hartley Transform in a Finite FieldFeb 16 2015The k-trigonometric functions over the Galois Field GF(q) are introduced and their main properties derived. This leads to the definition of the cask(.) function over GF(q), which in turn leads to a finite field Hartley Transform. The main properties of ... More
Degenerate and critical Bloch branesJul 03 2008In the last few years a number of works reported the appearance of thick branes with internal structure, induced by the parameter which controls the interaction between two scalar fields coupled to gravity in (4,1) dimensions in warped space-time with ... More
Genomic Imaging Based on Codongrams and a^2gramsMar 05 2015This paper introduces new tools for genomic signal processing, which can assist for genomic attribute extracting or describing biologically meaningful features embedded in a DNA. The codongrams and a2grams are offered as an alternative to spectrograms ... More
Efficient Multiplex for Band-Limited Channels: Galois-Field Division Multiple AccessMay 15 2015A new Efficient-bandwidth code-division-multiple-access (CDMA) for band-limited channels is introduced which is based on finite field transforms. A multilevel code division multiplex exploits orthogonality properties of nonbinary sequences defined over ... More
Radix-2 Fast Hartley Transform RevisitedMar 12 2015A Fast algorithm for the Discrete Hartley Transform (DHT) is presented, which resembles radix-2 fast Fourier Transform (FFT). Although fast DHTs are already known, this new approach bring some light about the deep relationship between fast DHT algorithms ... More
Degenerate and critical domain walls and accelerating universes driven by bulk particlesMar 31 2009We consider a scenario where our universe is taken as a three-dimensional domain wall embedded in a five-dimensional Minkowski space-time, as originally proposed by Brito and collaborators [1]. We explore the existence of a richer class of soliton solutions ... More
Asymmetrical bloch branes and the hierarchy problemNov 30 2013Apr 10 2014We investigate a two scalar fields split braneworld model which leads to a possible approach to the hierarchy problem within the thick brane scenario. The model exhibits a resulting asymmetric warp factor suitable for this purpose. The solution is obtained ... More
A method for obtaining thick branes modelsDec 17 2014Apr 19 2015In this work we present a new class of braneworld models, where the superpotential function may be decomposed in a very specific form, but still embracing, which allows considerable simplifications in the field equations. We exemplify the method with ... More
Introduction to Regge Calculus for GravitationApr 01 2019With the theory of general relativity, Einstein abolished the interpretation of gravitation as a force and associated it to the curvature of spacetime. Tensorial calculus and differential geometry are the mathematical resources necessary to study the ... More
Spin-dependent zero-bias peak in a hybrid nanowire-quantum dot system: Distinguishing isolated Majorana fermions from Andreev bound statesNov 26 2018Hybrid system composed by a semiconducting nanowire with proximity-induced superconductivity and a quantum dot at the end working as spectrometer was recently used to quantify the so-called degree of Majorana nonlocality [Deng et al., Phys.Rev.B, 98, ... More
Quantifying the decay of quantum properties in single-mode statesOct 31 2007Aug 07 2008The dissipative dynamics of Gaussian squeezed states (GSS) and coherent superposition states (CSS) are analytically obtained and compared. Time scales for sustaining different quantum properties such as squeezing, negativity of the Wigner function or ... More
The magnetization plateaus of the ferro and anti-ferro spin-1 classical models with $S_z^2$ termApr 18 2013We study in detail the exact thermodynamics of the one-dimensional standard and staggered spin-1 Ising models with a single-ion anisotropy term in the presence of a longitudinal magnetic field at low temperatures. The results are valid for the ferromagnetic ... More
Compactly Supported Wavelets Derived From Legendre Polynomials: Spherical Harmonic WaveletsFeb 03 2015A new family of wavelets is introduced, which is associated with Legendre polynomials. These wavelets, termed spherical harmonic or Legendre wavelets, possess compact support. The method for the wavelet construction is derived from the association of ... More
On the Determination of the Rotational Oblateness of AchernarJan 31 2008The recent interferometric study of Achernar, leading to the conclusion that its geometrical oblateness cannot be explained in the Roche approximation, has stirred substantial interest in the community, in view of its potential impact in many fields of ... More
Redistribution of light frequency by multiple scattering in a resonant atomic vaporJun 18 2015The propagation of light in a resonant atomic vapor can \textit{a priori} be thought of as a multiple scattering process, in which each scattering event redistributes both the direction and the frequency of the photons. Particularly, the frequency redistribution ... More
Gravitational field of an infinitely long supermassive cosmic stringNov 18 1994We obtain an exact solution of the coupled Einstein-scalar-gauge field equations for a local infinitely long supermassive cosmic string. The solution correponds to that of Hiscock-Gott . The string appears to be due to the freezing of the scalar field ... More
Structural and magnetic transition in CeFeAsO: separated or connected?Jan 25 2010May 05 2010Using an adapted Sn-flux growth technique we obtained comparatively large CeFeAsO single crystals of better quality than previously reported polycrystals or single crystals, as evidenced by much sharper anomalies at the structural and magnetic phase transitions ... More
Critical behavior of the S=1/2 Heisenberg ferromagnet: A Handscomb quantum Monte Carlo studyApr 11 2000We investigate the critical relaxational dynamics of the S=1/2 Heisenberg ferromagnet on a simple cubic lattice within the Handscomb prescription on which it is a diagrammatic series expansion of the partition function that is computed by means of a Monte ... More
Rare earth magnetism in CeFeAsO: A single crystal studySep 04 2009Oct 30 2009Single crystals of CeFeAsO, large enough to study the anisotropy of the magnetic properties, were grown by an optimized Sn-flux technique. The high quality of our single crystals is apparent from the highest residual resistivity ratio, RRR = 12, reported ... More
Generalized Heisenberg Algebras and Fibonacci SeriesFeb 15 2007We have constructed a Heisenberg-type algebra generated by the Hamiltonian, the step operators and an auxiliar operator. This algebra describes quantum systems having eigenvalues of the Hamiltonian depending on the eigenvalues of the two previous levels. ... More
Effect of Interdots Electronic Repulsion in the Majorana Signature for a Double Dot InterferometerNov 03 2015Dec 11 2015We investigate theoretically the features of the Majorana hallmark in the presence of Coulomb repulsion between two quantum dots describing a spinless Aharonov-Bohm-like interferometer, where one of the dots is strongly coupled to a Kitaev wire within ... More
Method of approximation for potentials in impenetrable boxes: Harmonic Oscillator and Coulomb potentialsFeb 07 2002In this work we develop an approach to obtain analytical expressions for potentials in an impenetrable box. It is illustrated through the particular cases of the harmonic oscillator and the Coulomb potential. In this kind of system the energy expression ... More
Differential interferometric phases at high spectral resolution as a sensitive physical diagnostic of circumstellar disksJun 05 2013Context. The circumstellar disks ejected by many rapidly rotating B stars (so-called Be stars) offer the rare opportunity of studying the structure and dynamics of gaseous disks at high spectral as well as angular resolution. Aims. This paper explores ... More
Lattice effects and entropy release at the low-temperature phase transition in the spin-liquid candidate $κ$-(BEDT-TTF)$_{2}$Cu$_{2}$(CN)$_{3}$Sep 03 2009Jan 08 2010The spin-liquid candidate $\kappa$-(BEDT-TTF)$_{2}$Cu$_{2}$(CN)$_{3}$ has been studied by measuring the uniaxial expansion coefficients $\alpha_{i}$, the specific heat, and magnetic susceptibility. Special emphasis was placed on the mysterious anomaly ... More
On the CQE Phase Signature Feature in High-Resolution Spectro-Interferometry of Be StarsAug 07 2012We analyse a feature that is detectable at the differential phases of high-resolution spectro-interferometry of Be stars. The origin of this feature (dubbed CQE-PS, Central Quasi Emission Phase Signature) lies in the differential absorption of photospheric ... More
Evidence for Lattice Effects at the Charge-Ordering Transition in (TMTTF)$_2$XJul 04 2008Nov 24 2008High-resolution thermal expansion measurements have been performed for exploring the mysterious "structureless transition" in (TMTTF)$_{2}$X (X = PF$_{6}$ and AsF$_{6}$), where charge ordering at $T_{CO}$ coincides with the onset of ferroelectric order. ... More
Anomalous Lattice Response at the Mott Transition in a Quasi-2D Organic ConductorOct 20 2006Dec 11 2007Discontinuous changes of the lattice parameters at the Mott metal-insulator transition are detected by high-resolution dilatometry on deuterated crystals of the layered organic conductor $\kappa$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br. The uniaxial expansivities ... More
Fermion localization on degenerate and critical branesNov 08 2010Mar 24 2011In this work we analyze the localization of fermions on degenerate and critical Bloch branes. This is done directly on physical coordinates, in constrast to some works that has been using conformal coordinates. We find the range of coupling constants ... More
Equivalence between non-bilinear spin-$S$ Ising model and Wajnflasz modelFeb 10 2011Jun 16 2012We propose the mapping of polynomial of degree 2S constructed as a linear combination of powers of spin-$S$ (for simplicity, we called as spin-$S$ polynomial) onto spin-crossover state. The spin-$S$ polynomial in general can be projected onto non-symmetric ... More
Direct algebraic mapping transformation for decorated spin modelsFeb 10 2011Apr 15 2011In this article we propose a general transformation for decorated spin models. The advantage of this transformation is to perform a direct mapping of a decorated spin model onto another effective spin thus simplifying algebraic computations by avoiding ... More
Geometric Quantization of Topological Gauge TheoriesDec 20 1993We study the symplectic quantization of Abelian gauge theories in $2+1$ space-time dimensions with the introduction of a topological Chern-Simons term.
Primordial scalar perturbations in tachyonic power-law inflationJan 20 2013Jan 31 2014In this work we determine the power spectrum of the gravitational potential of the primordial fluctuations for an inflationary model whose \emph{inflaton} is a non-canonical scalar field of the tachyon-type. The respective background field equations for ... More
Quasi-phases and pseudo-transitions in one-dimensional models with nearest neighbor interactionsSep 07 2017There are some particular one-dimensional models, such as the Ising-Heisenberg spin models with a variety of chain structures, which exhibit unexpected behaviors quite similar to the first and second order phase transition, which could be confused naively ... More
Discrete and finite Genral RelativityJan 13 1998Nov 24 1998We develop the General Theory of Relativity in a formalism with extended causality that describes physical interaction through discrete, transversal and localized pointlike fields. The homogeneous field equations are then solved for a finite, singularity-free, ... More
Gauss vs Coulomb and the Cosmological Mass-deficit ProblemMar 18 1999In a previous work General Relativity has been presented as a microscopic theory of finite and discrete point-like fields that we associate to a classical description of gravitons. The standard macroscopic continuous field is retrieved as an average-valued ... More
Cosmic expansion from boson and fermion fieldsApr 06 2011Oct 13 2013This paper consists in analyzing an action that describes boson and fermion fields minimally coupled to the gravity and a common matter field. The self-interaction potentials of the fields are not chosen a priori but from the Noether symmetry approach. ... More
Dark Sector from Interacting Canonical and Non-Canonical Scalar FieldsJun 16 2010Oct 13 2013In this work it is investigated general models with interactions between two canonical scalar fields and between one non-canonical (tachyon-type) and one canonical scalar field. The potentials and couplings to the gravity are selected through the Noether ... More
Constraining condensate dark matter in galaxy clustersNov 26 2014Aug 06 2015We constrain scattering length parameters in a Bose-Einstein condensate dark matter model by using galaxy clusters radii, with the implementation of a method previously applied to galaxies. At the present work, we use a sample of 114 clusters radii in ... More
A set of exactly solvable Ising models with half-odd-integer spinMay 05 2008Apr 23 2009We present a set of exactly solvable Ising models, with half-odd-integer spin-S on a square-type lattice including a quartic interaction term in the Hamiltonian. The particular properties of the mixed lattice, associated with mixed half-odd-integer spin-(S,1/2) ... More
Dirac equation exact solutions for generalized asymmetrical Hartmann potentialsMay 23 2007In this work we solve the Dirac equation by constructing the exact bound state solutions for a mixing of vector and scalar generalized Hartmann potentials. This is done provided the vector potential is equal to or minus the scalar potential. The cases ... More
Effective multifractal features and l-variability diagrams of high-frequency price fluctuations time seriesNov 16 2007In this manuscript we present a comprehensive study on the multifractal properties of high-frequency price fluctuations and instantaneous volatility of the equities that compose Dow Jones Industrial Average. The analysis consists about quantification ... More
Noether symmetry for non-minimally coupled fermion fieldsJul 12 2008Sep 04 2008A cosmological model where a fermion field is non-minimally coupled with the gravitational field is studied. By applying Noether symmetry the possible functions for the potential density of the fermion field and for the coupling are determined. Cosmological ... More
NGC 4608 and NGC 5701: Barred Galaxies without Disks?Jan 06 2003We have performed for the first time in the literature a 2D structural analysis on the barred lenticular and face--on galaxies NGC 4608 and NGC 5701. The results indicate that these galaxies either have never had large disks or their disks were almost ... More
Multiflavor SolderingDec 22 2007In two dimensions the simple addition of two chiral bosons of opposite chiralities does not lead to a full massless scalar field. Similarly, in three dimensions the addition of two Maxwell-Chern-Simons fields of opposite helicities $\pm 1$ will not produce ... More
Comment on ``Anyon in an External Eletromagnetic Field: Hamiltonian and Lagrangian Formulations''Feb 09 1994We comment on a recent paper by Chaichian et al. (Phys.Rev.Lett. 71(1993)3405).
The stifness of the supranuclear equation of state (once again)Jan 31 2017We revisit the present status of the stiffness of the supranuclear equations of state, particularly the solutions that increase the stiffness in the presence of hyperons, the putative transition to a quark matter phase and the robustness of massive compact ... More
On the Lengths, Colors and Ages of 18 Face-On BarsNov 29 2005Along with a brief analysis we present data obtained from BVRI and Ks images of a sample of 19 galaxies (18 barred and 1 unbarred) which will be further explored in a future paper. We measured the lengths and colors of the bars, created color maps and ... More
Free Relativistic Anyons with Canonical Spin AlgebraNov 10 1994Dec 01 1994We discuss a relativistic free particle with fractional spin in 2+1 dimensions, where the dual spin components satisfy the canonical angular momentum algebra $\left\{ S_\mu , S_\nu \right\}\,=\,\epsilon_{\mu \nu \gamma}S^\gamma $. It is shown that it ... More
Dating Secular Evolution: Bar Ages from Stellar KinematicsAug 23 2005The last few years witnessed a change of perspective in the context of galaxy formation and evolution. The major role played by bars in the history of these fundamental building blocks of our universe was finally realized. However, and despite the fact ... More
Restrictions over two-dimensional gauge models with Thirring-like interactionDec 22 2007Some years ago, it was shown how fermion self-interacting terms of the Thirring-type impact the usual structure of massless two-dimensional gauge theories [1]. In that work only the cases of pure vector and pure chiral gauge couplings have been considered ... More
A Simple Action for a Free AnyonApr 16 1997By studying classical realizations of the sl(2,R) algebra in a two dimensional phase space $(q,\pi)$, we have derived a continuous family of new actions for free anyons in 2+1 dimensions. For the case of light-like spin vector $(S_\mu S^\mu =0)$, the ... More
Quantization of Maxwell-Chern-Simons-Podolsky TheoryMar 28 1994We quantize a generalized electromagnetism in 2 + 1 dimensions which contains a higher-order derivative term by using Dirac's method. By introducing auxiliary fields we transform the original theory in a lower-order derivative one which can be treated ... More
The Vertical Stellar Kinematics in Face-On Barred Galaxies: Estimating the Ages of BarsApr 28 2005In order to perform a detailed study of the stellar kinematics in the vertical axis of bars, we obtained high signal-to-noise spectra along the major and minor axes of the bars in a sample of 14 face-on galaxies, and used them to determine the line of ... More
A New Challenge: Bar Formation and Secular Evolution in Lenticular GalaxiesSep 24 2002To further enhance our understanding on the formation and evolution of bars in lenticular (S0) galaxies, we are undertaking a detailed photometric and spectroscopic study on a sample of 22 objects. Here we report the results of a 2D structural analysis ... More
Spinless fermion model on diamond chainDec 14 2010The decoration or iteration transformation was widely applied to solve exactly the magnetic spin models in one-dimensional and two-dimensional lattice. The motif of this letter is to extend the decoration transformation approach for models that describe ... More
Cosmological models with spinor and scalar fields by Noether symmetry approachJan 22 2013Oct 13 2013General cosmological models with spinor and scalar fields playing the role of gravitational sources are analyzed. The Noether symmetry approach is taken as a criterion to constrain the undefined potentials and couplings of the generic actions. For all ... More
Conformal coupling associated with the Noether symmetry and its connection with the $Λ$CDM dynamicsJan 22 2013Oct 13 2013The aim of the present work is to investigate a non-minimally coupled scalar field model through the Noether symmetry approach, with the radiation, matter and cosmological constant eras being analyzed. The Noether symmetry condition allows a conformal ... More
Constraining non-minimally coupled tachyon fields by Noether symmetrySep 13 2008May 26 2009A model for a spatially flat homogeneous and isotropic Universe whose gravitational sources are a pressureless matter field and a tachyon field non-minimally coupled to the gravitational field is analyzed. Noether symmetry is used to find the expressions ... More
An upper limit on the cosmic-ray luminosity of individual sources from gamma-ray observationsNov 19 2013Different types of extragalactic objects are known to produce TeV gamma-rays. Some of these objects are the most probable candidates to accelerate cosmic rays up to 10^20 eV. It is very well known that gamma-rays can be produced as a result of the cosmic ... More
Quantum phase estimation with squeezed quasi-Bell statesSep 01 2016Sep 23 2016In this paper we analyze the quantum phase estimation problem using continuous-variable, entangled squeezed coherent states (quasi-Bell states). We calculate the quantum Fisher information having the quasi-Bell states as probe states and find that both ... More
Shape of the Galactic Orbits in ClustersJan 21 1998A kinematical analysis applied to a sample of galaxy clusters indicates that the differences between the velocity distribution of elliptical and spiral galaxies are associated with the shape of their orbit families. The orbital anisotropies present on ... More
On the Lengths, Colours and Ages of BarsOct 26 2006In an effort to obtain further observational evidences for secular evolution processes in galaxies, as well as observational constraints to current theoretical models of secular evolution, we have used BVRI and Ks images of a sample of 18 barred galaxies ... More