Results for "Rogelma M. S. Ferreira"

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Anomalous law of coolingDec 15 2014Mar 04 2015We analyze the temperature relaxation phenomena of systems in contact with a thermal reservoir that undergo a non-Markovian diffusion process. From a generalized Langevin equation, we show that the temperature is governed by a law of cooling of the Newton's ... More
Anomalous diffusion: A basic mechanism for the evolution of inhomogeneous systemsFeb 08 2019In this article we review classical and recent results in anomalous diffusion and provide mechanisms useful for the study of the fundamentals of certain processes, mainly in condensed matter physics, chemistry and biology. Emphasis will be given to some ... More
Pattern transitions in a nonlocal logistic map for populationsJan 26 2016Sep 14 2016In this work, we study the pattern solutions of doubly nonlocal logistic map that include spatial kernels in both growth and competition terms. We show that this map includes as a particular case the nonlocal Fisher-Kolmogorov equation, and we demonstrate ... More
Exchange coupling between magnetic layers across non-magnetic superlatticesMay 30 1997Jun 01 1997The oscillation periods of the interlayer exchange coupling are investigated when two magnetic layers are separated by a metallic superlattice of two distinct non-magnetic materials. In spite of the conventional behaviour of the coupling as a function ... More
The Ellis semigroup of a nonautonomous discrete dynamical systemFeb 26 2016We introduce the {\it Ellis semigroup} of a nonautonomous discrete dynamical system $(X,f_{1,\infty})$ when $X$ is a metric compact space. The underlying set of this semigroup is the pointwise closure of $\{f\sp{n}_1 \, |\, n\in \mathbb{N}\}$ in the space ... More
Electronic structure of graphene beyond the linear dispersion regimeOct 05 2010Nov 15 2012Among the many interesting features displayed by graphene, one of the most attractive is the simplicity with which its electronic structure can be described. The study of its physical properties is significantly simplified by the linear dispersion relation ... More
The geometry of Hrushovski constructions, I. The uncollapsed caseMar 18 2011An intermediate stage in Hrushovski's construction of flat strongly minimal structures in a relational language L produces omega-stable structures of rank omega. We analyze the pregeometries given by forking on the regular type of rank omega in these ... More
Monte-Carlo phase diagram of a Hubbard-Peierls model in the search for spin crossover transition in $π$-conjugated polymersDec 16 2010We present a Monte Carlo study of the finite temperature properties of an extended Hubbard-Peierls model describing one dimensional $\pi$-conjugated polymers. The model incorporates electron-phonon and hyperfine interaction and it is solved at the mean ... More
Electronic transport on carbon nanotube networks: a multiscale computational approachFeb 21 2013Carbon nanotube networks are one of the candidate materials to function as malleable, transparent, conducting films, with the technologically promising application of being used as flexible electronic displays. Nanotubes disorderly distributed in a film ... More
Non-relativistic electron-electron interaction in a Maxwell-Chern-Simons-Proca model endowed with a timelike Lorentz-violating backgroundJan 30 2006Nov 14 2006A planar Maxwell-Chern-Simons-Proca model endowed with a Lorentz-violating background is taken as framework to investigate the electron-electron interaction. The Dirac sector is introduced exhibiting a Yukawa and a minimal coupling with the scalar and ... More
The geometry of Hrushovski constructions, II. The strongly minimal caseMar 18 2011We investigate the isomorphism types of combinatorial geometries arising from Hrushovski's flat strongly minimal structures and answer some questions from Hrushovski's original paper.
First order quantum phase transitionsOct 23 2006Quantum phase transitions have been the subject of intense investigations in the last two decades [1]. Among other problems, these phase transitions are relevant in the study of heavy fermion systems, high temperature superconductors and Bose-Einstein ... More
Strictly Canonical Quantization of a Massless Spinning Particle and a Quaternionic Extension of Pseudoclassical MechanicsOct 14 2005A pseudoclassical model, reproducing, upon quantization, the dynamics of the chiral sectors of the massless spin-1/2 field theory is proposed. The discrete symmetries of the action are studied in details. In order to reproduce the positive and negative ... More
Assessment of 48 Stock markets using adaptive multifractal approachFeb 19 2015Jul 06 2017Stock market comovements are examined using cointegration, Granger causality tests and nonlinear approaches in context of mutual information and correlations. Underlying data sets are affected by non-stationarities and trends, we also apply AMF-DFA and ... More
The structures of embedded clusters in the Perseus, Serpens and Ophiuchus molecular cloudsMay 14 2008The young stellar population data of the Perseus, Ophiuchus and Serpens molecular clouds are obtained from the Spitzer c2d legacy survey in order to investigate the spatial structure of embedded clusters using the nearest neighbour and minimum spanning ... More
Fighting cancer with virusSep 09 2003One of the most promising strategies to treat cancer is attacking it with viruses. Virus can kill tumor cells specifically or act as carriers that deliver normal genes into cancer cells. A model for virus therapy of cancer is investigated and some of ... More
Quantum corrections to the phase diagram of heavy-fermion superconductorsMar 07 2005The competition between magnetism and Kondo effect is the main effect determining the phase diagram of heavy fermion systems. It gives rise to a quantum critical point which governs the low temperature properties of these materials. However, experimental ... More
Global well-posedness and symmetries for dissipative active scalar equations with positive-order couplingsMay 14 2013Jan 02 2014We consider a family of dissipative active scalar equations outside the $L^{2}$-space. This was introduced in [D. Chae, P. Constantin, J. Wu, to appear in IUMJ (2014)] and its velocity fields are coupled with the active scalar via a class of multiplier ... More
Gradient Method for Optimization on Riemannian Manifolds with Lower Bounded CurvatureJun 07 2018The gradient method for minimize a differentiable convex function on Riemannian manifolds with lower bounded sectional curvature is analyzed in this paper. The analysis of the method is presented with three different finite procedures for determining ... More
Lorentz-violating contributions of the Carroll-Field-Jackiw model to the CMB anisotropyOct 01 2008Dec 11 2008We study the finite temperature properties of the Maxwell-Carroll-Field-Jackiw (MCFJ) electrodynamics for a purely spacelike background. Starting from the associated finite temperature partition function, a modified black body spectral distribution is ... More
Self-similar solutions for active scalar equations in Fourier-Besov-Morrey spacesSep 20 2013Feb 13 2014We are concerned with a family of dissipative active scalar equation with velocity fields coupled via multiplier operators that can be of high-order. We consider sub-critical values for the fractional diffusion and prove global well-posedness of solutions ... More
Strategies for Optimize Off-Lattice Aggregate SimulationsApr 13 2008We review some computer algorithms for the simulation of off-lattice clusters grown from a seed, with emphasis on the diffusion-limited aggregation, ballistic aggregation and Eden models. Only those methods which can be immediately extended to distinct ... More
Stock market comovements: nonlinear approach for 48 countriesFeb 19 2015This paper examines the stock market comovements using basically three different approaches. Firstly, we used the most common linear analysis, based on cointegration and Granger causality tests; secondly we applied a nonlinear approach, using mutual information ... More
Multi-band quantum ratchetsAug 28 2002We investigate directed motion in non-adiabatically rocked ratchet systems sustaining few bands below the barrier. Upon restricting the dynamics to the lowest M bands, the total system-plus-bath Hamiltonian is mapped onto a discrete tight-binding model ... More
Transition on the entropic elasticity of DNA induced by intercalating moleculesApr 18 2007We use optical tweezers to perform stretching experiments on DNA molecules when interacting with the drugs daunomycin and ethidium bromide, which intercalate the DNA molecule. These experiments are performed in the low-force regime from zero up to 2 pN. ... More
A reaction-diffusion model for the growth of avascular tumorSep 25 2001Nov 20 2001A nutrient-limited model for avascular cancer growth including cell proliferation, motility and death is presented. The model qualitatively reproduces commonly observed morphologies for primary tumors, and the simulated patterns are characterized by its ... More
Morphology transitions induced by chemotherapy in carcinomas "in situ"Dec 30 2002Recently, we have proposed a nutrient-limited model for the avascular growth of tumors including cell proliferation, motility and death \cite{jr}, that, qualitatively reproduces commonly observed morphologies for carcinomas {\it in situ}. In the present ... More
Williams and Bjerknes model with growth limitationNov 19 2001Williams and Bjerknes proposed a simple stochastic growth model to describe the tumor growth in the basal layer of an epithelium. In this work we generalize this model by including the possibility of saturation in the tumor growth as it is clinically ... More
Effects of the Screening Breakdown in the Diffusion-Limited Aggregation ModelMar 20 2004Several models based on the diffusion-limited aggregation (DLA) model were proposed and their scaling properties explored by computational and theoretical approaches. In this paper, we consider a new extension of the on-lattice DLA model in which the ... More
Some Notes on Complex Symmetric OperatorsSep 25 2017Feb 10 2019In this paper we show that every conjugation $C$ on the Hardy-Hilbert space $H^{2}$ is of type $C=T^{*}C_{1}T$, where $T$ is an unitary operator and $C_{1}f\left(z\right)=\overline{f\left(\overline{z}\right)}$, with $f\in H^{2}$. In the sequence, we extend ... More
Critical behavior of the contact process on small-world networksJul 23 2013Nov 11 2013We investigate the role of clustering on the critical behavior of the contact process (CP) on small-world networks using the Watts-Strogatz (WS) network model with an edge rewiring probability p. The critical point is well predicted by a homogeneous cluster-approximation ... More
One-loop stau masses in the effective potential approachJul 27 2001Jul 30 2001We calculate the one-loop contributions to the tau slepton masses in the Minimal Supersymmetric Standard Model in the effective potential approach. For the majority of parameter space under study, those corrections are shown to elevate the value of the ... More
One-loop charge and colour breaking associated with the top Yukawa couplingJun 21 2004Jan 28 2005We calculate the one-loop contributions to the MSSM effective potential when the scalar top fields have non-zero vacuum expectation values and study their impact on charge and colour breaking bounds.
A full one-loop charge symmetry breaking effective potentialAug 11 2000Jun 12 2001We calculate the one-loop contributions to the effective potential for the minimal supersymmetric model when scalar fields other than the Higgses have vacuum expectation values. The importance of these contributions for studies of charge and colour breaking ... More
Low-energy Moller scattering in a Maxwell-Chern-Simons Lorentz-violating planar modelMar 29 2004One starts from a planar Maxwell-Chern-Simons model endowed with a Lorentz-violating term. The Dirac sector is introduced exhibiting a Yukawa and a minimal coupling with the scalar scalar and the gauge fields, respectively. One then evaluates the electron-electron ... More
Quasi-stationary simulations of the directed percolation universality class in d = 3 dimensionsJan 05 2011Jan 07 2011We present quasi-stationary simulations of three-dimensional models with a single absorbing configuration, namely the contact process (CP), the susceptible-infected-susceptible (SIS) model and the contact replication process (CRP). The moment ratios of ... More
Questing for an optimal, universal viral agent for oncolytic virotherapySep 16 2011One of the most promising strategies to treat cancer is attacking it with viruses designed to exploit specific altered pathways. Here, the effects of oncolytic virotherapy on tumors having compact, papillary and disconnected morphologies are investigated ... More
Indirect exchange coupling between localized magnetic moments in carbon nanotubes: a dynamic approachFeb 29 2008Magnetic moments dilutely dispersed in a metallic host tend to be coupled through the conduction electrons of the metal. This indirect exchange coupling, known to occur for a variety of magnetic materials embedded in several different metallic structures, ... More
Dimensional reduction of the CPT-even electromagnetic sector of the Standard Model ExtensionJul 13 2011The CPT-even abelian gauge sector of the Standard Model Extension is represented by the Maxwell term supplemented by $(K_{F})_{\mu\nu\rho\sigma}F^{\mu\nu}F^{\rho\sigma}$, where the Lorentz-violating background tensor, $(K_{F})_{\mu\nu\rho\sigma}$, possesses ... More
Limiting temperature from microscopic equation of stateFeb 02 2004The limiting temperature $T_{lim}$ of a series of nuclei is calculated employing a set of microscopic nuclear Equations of State (EoS). It is shown that the value of $T_{lim}$ is sensitive to the nuclear matter Equation of State used. Comparison with ... More
Evolution of ThingsJun 01 2011Evolution is one of the major omnipresent powers in the universe that has been studied for about two centuries. Recent scientific and technical developments make it possible to make the transition from passively understanding to actively mastering evolution. ... More
Non-collinear coupling between magnetic adatoms in carbon nanotubesFeb 28 2007The long range character of the exchange coupling between localized magnetic moments indirectly mediated by the conduction electrons of metallic hosts often plays a significant role in determining the magnetic order of low-dimensional structures. In addition ... More
Indirect exchange coupling between magnetic adatoms in carbon nanotubesMar 23 2005The long range character of the exchange coupling between localized magnetic moments indirectly mediated by the conduction electrons of metallic hosts can play a significant role in determining the magnetic order of low-dimensional structures. Here we ... More
A one-dimensional model for the growth of CdTe quantum dots on Si substratesJan 03 2006Recent experiments involving CdTe films grown on Si(111) substrates by hot wall epitaxy revealed features not previously observed [S. O. Ferreira \textit{et al.}, J. Appl. Phys. \textbf{93}, 1195 (2003)]. This system, which follows the Volmer-Weber growth ... More
Dynamic RKKY interaction between magnetic moments in graphene nanoribbonsDec 09 2016Graphene has been identified as a promising material with numerous applications, particularly in spintronics. In this paper we investigate the peculiar features of spin excitations of magnetic units deposited on graphene nanoribbons and how they can couple ... More
Graphene as a non-magnetic spin-current lensSep 30 2010Apr 14 2011In spintronics, the ability to transport magnetic information often depends on the existence of a spin current traveling between two different magnetic objects acting as source and probe. A large fraction of this information never reaches the probe and ... More
Variable range of the RKKY interaction in edged grapheneAug 29 2013The indirect exchange interaction is one of the key factors in determining the overall alignment of magnetic impurities embedded in metallic host materials. In this work we examine the range of this interaction in magnetically-doped graphene systems in ... More
Orthorhombic to tetragonal phase transition and superconductivity in the Ba2Cu3O4Cl2 compoundJun 20 2006In this work we have investigated the orthorhombic to tetragonal phase transition in the Ba2Cu3O4Cl2 compound. This transition was observed by X-ray powder diffractometry carried out in samples heat treated between 700 and 750OC and also in samples with ... More
Time-dependent Modeling of Pulsar Wind NebulaeSep 27 2013A spatially independent model that calculates the time evolution of the electron spectrum in a spherically expanding pulsar wind nebula (PWN) is presented, allowing one to make broadband predictions for the PWN's non-thermal radiation. The source spectrum ... More
Ionization rates in the heliosheath and in astrosheathsDec 09 2013In the heliosphere, especially in the inner heliosheath, mass-, momentum-, and energy loading induced by the ionization of neutral interstellar species plays an important, but for some species, especially Helium, an underestimated role. We discuss the ... More
Magnetization profile for impurities in graphene nanoribbonsAug 31 2011The magnetic properties of graphene-related materials and in particular the spin-polarised edge states predicted for pristine graphene nanoribbons (GNRs) with certain edge geometries have received much attention recently due to a range of possible technological ... More
Dynamic RKKY interaction in grapheneDec 01 2011Feb 21 2012The growing interest in carbon-based spintronics has stimulated a number of recent theoretical studies on the RKKY interaction in graphene, based on which the energetically favourable alignment between magnetic moments embedded in this material can be ... More
Impurity segregation in graphene nanoribbonsSep 08 2009Nov 23 2009The electronic properties of low-dimensional materials can be engineered by doping, but in the case of graphene nanoribbons (GNR) the proximity of two symmetry-breaking edges introduces an additional dependence on the location of an impurity across the ... More
Heterogeneous pair-approximation for the contact process on complex networksFeb 12 2014May 07 2014Recent works have shown that the contact process running on the top of highly heterogeneous random networks is described by the heterogeneous mean-field theory. However, some important aspects as the transition point and strong corrections to the finite-size ... More
Numerical simulations of composite supernova remnants for small $σ$ pulsar wind nebulaeSep 24 2013Composite supernova remnants consist of a pulsar wind nebula located inside a shell-type remnant. The presence of a shell has implications on the evolution of the nebula, although the converse is generally not true. The purpose of this paper is two-fold. ... More
WFCAM, Spitzer-IRAC and SCUBA observations of the massive star forming region DR21/W75: II. Stellar content and star formationOct 04 2006Wide field near-infrared observations and Spitzer Space Telescope IRAC observations of the DR21/W75 star formation regions are presented. The photometric data are used to analyse the extinction, stellar content and clustering in the entire region by using ... More
Einstein-Hilbert Graviton modes modified by the Lorentz-violating bumblebee FieldFeb 14 2014Jul 10 2014In this work, we investigate the consequences of the spontaneous breaking of Lorentz symmetry, triggered by the bumblebee vector field, on the usual Einstein-Hilbert theory. Specifically, we consider the Einstein-Hilbert action modified by the bumblebee ... More
Fermion localization and resonances on two-field thick branesJan 22 2009Jul 05 2009We consider $(4,1)$-dimensional branes constructed with two scalar fields $\phi$ and $\chi$ coupled to a Dirac spinor field by means of a general Yukawa coupling. The equation of motion for the coefficients of the chiral decomposition of the spinor in ... More
Fundamental Oscillation Periods of the Interlayer Exchange Coupling beyond the RKKY ApproximationOct 10 1996A general method for obtaining the oscillation periods of the interlayer exchange coupling is presented. It is shown that it is possible for the coupling to oscillate with additional periods beyond the ones predicted by the RKKY theory. The relation between ... More
Minimisation of a one-loop charge breaking effective potentialFeb 12 2001Jun 25 2001We compute the field derivatives of a one-loop charge breaking effective potential and analyse their effect in its minimisation. The impact on charge breaking bounds on the MSSM parameters is discussed.
Electron-electron interaction in a MCS model with a purely spacelike Lorentz-violating backgroundSep 30 2004Oct 04 2004One considers a planar Maxwell-Chern-Simons electrodynamics in the presence of a purely spacelike Lorentz-violating background. Once the Dirac sector is properly introduced and coupled to the scalar and the gauge fields, the electron-electron interaction ... More
DNA NanoroboticsAug 10 2007This paper presents a molecular mechanics study for new nanorobotic structures using molecular dynamics (MD) simulations coupled to virtual reality (VR) techniques. The operator can design and characterize through molecular dynamics simulation the behavior ... More
The vacuum structure of the Higgs complex singlet-doublet modelJul 20 2016Aug 01 2016The complex singlet-doublet model is a popular theory to account for dark matter and electroweak baryogenesis, wherein the Standard Model particle content is supplemented by a complex scalar gauge singlet, with certain discrete symmetries imposed. The ... More
RKKY interaction between adsorbed magnetic impurities in graphene: symmetry and strain effectsJul 04 2013The growing interest in carbon-based spintronics has stimulated a number of recent theoretical studies on the RKKY interaction in graphene, with the aim of determining the most energetically favourable alignments between embedded magnetic moments. The ... More
Strain-induced modulation of magnetic interactions in grapheneJul 12 2012Nov 20 2012The ease with which the physical properties of graphene can be tuned suggests a wide range of possible applications. Recently, strain engineering of these properties has been of particular interest. Possible spintronic applications of magnetically doped ... More
Omnidirectional Gravitational Wave Detector with a Laser-Interferometric Gravitational CompassSep 20 2016Based on the Szekeres-Pirani gravitational compass we suggest the addition of a fourth, non-coplanar mass/mirror to the presently existing laser based gravitational wave observatories, enabling them to operate omnidirectionally, to filter out ambiguous ... More
Repulsive Core of NN S-Wave Scattering in a Quark Model with a Condensed VacuumMar 04 1997We work in a chiral invariant quark model, with a condensed vacuum, characterized by only one parameter. Bound state equations for the nucleon and Delta are solved in order to obtain an updated value of their radii and masses. Nucleon-nucleon S-Wave scattering ... More
Strongly coupling a cavity to inhomogeneous ensembles of emitters : potential for long lived solid-state quantum memoriesJan 10 2011Sep 02 2011We investigate theoretically the coupling of a cavity mode to a continuous distribution of emitters. We discuss the influence of the emitters inhomogeneous broadening on the existence and on the coherence properties of the polaritonic peaks. We find that ... More
Upper bound for the conductivity of nanotube networksJun 26 2009Sep 02 2009Films composed of nanotube networks have their conductivities regulated by the junction resistances formed between tubes. Conductivity values are enhanced by lower junction resistances but should reach a maximum that is limited by the network morphology. ... More
Spontaneous symmetry breaking in amnestically induced persistenceAug 22 2007Sep 11 2007We investigate a recently proposed non-Markovian random walk model characterized by loss of memories of the recent past and amnestically induced persistence. We report numerical and analytical results showing the complete phase diagram, consisting of ... More
Strain-Modified RKKY Interaction in Carbon NanotubesMay 12 2015For low-dimensional metallic structures, such as nanotubes, the exchange coupling between localized magnetic dopants is predicted to decay slowly with separation. The long-range character of this interaction plays a significant role in determining the ... More
Graphene-based spin-pumping transistorMar 07 2010We demonstrate with a fully quantum-mechanical approach that graphene can function as gate-controllable transistors for pumped spin currents, i.e., a stream of angular momentum induced by the precession of adjacent magnetizations, which exists in the ... More
Time-dependent modelling of pulsar wind nebulaeAug 07 2013A spatially-independent model that can be used to calculate the temporal evolution of the electron/ positron spectrum in a spherically expanding pulsar wind nebula is presented. The model is applied to the young nebula G21.5-0.9, as well as to the unidentified ... More
Particle Production in Ekpyrotic ScenariosMay 16 2016We consider Parker particle production in the Ekpyrotic scenario (in particular in the New Ekpyrotic model) and show that the density of particles produced by the end of the phase of Ekpyrotic contraction is sufficient to lead to a hot state of matter ... More
Macroscopic transport of a current-induced spin polarizationAug 24 2016Experimental studies of spin transport in a two-dimensional electron gas hosted by a triple GaAs/AlGaAs quantum well are reported. Using time-resolved Kerr rotation, we observed the precession of the spin polarization about a current-controlled spin-orbit ... More
One-loop contributions to neutral minima in the inert doublet modelNov 09 2015Aug 14 2016The vacuum structure of the inert doublet model is analysed at the one-loop level using the effective potential formalism, to verify the validity of tree-level predictions for the properties of the global minimum. An inert minimum (with massive fermions) ... More
New textures for the lepton mass matricesNov 03 2014Dec 02 2014We study predictive textures for the lepton mass matrices in which the charged-lepton mass matrix has either four or five zero matrix elements while the neutrino Majorana mass matrix has, respectively, either four or three zero matrix elements. We find ... More
Scattering by infinitely rising one-dimensional potentialsNov 23 2017Infinitely rising one-dimensional potentials constitute impenetrable barriers which reflect totally any incident wave. However, the scattering by such kind of potentials is not structureless: resonances may occur for certain values of the energy. Here ... More
Contributions from dimension six strong flavor changing operators to top anti-top, top plus gauge boson, and top plus Higgs boson production at the LHCApr 17 2006May 04 2006We study the effects of a set of dimension six flavor changing effective operators on several processes of production of top quarks at the LHC. Namely, top anti-top production and associated production of a top and a gauge or Higgs boson. Analytical expressions ... More
Generalized Jordan derivations on semiprime ringsApr 30 2018The purpose of this note is to prove the following. Suppose $\R$ is a semiprime unity ring having an idempotent element e $\left(e \neq 0, e \neq 1\right)$ which satisfies mild conditions. It is shown that every additive generalized Jordan derivation ... More
Form Factors and Decay Rates for Heavy $Λ$ Semileptonic Decays from QCD Sum RulesMar 11 1999QCD sum rules for the determination of form factors of $\Lambda_b$ and $\Lambda_c$ semileptonic decays are investigated. With a form for the baryonic current appropriate for the limits of the heavy quark symmetries, the different tensor structures occurring ... More
Contact process on a Voronoi triangulationOct 01 2008We study the continuous absorbing-state phase transition in the contact process on the Voronoi-Delaunay lattice. The Voronoi construction is a natural way to introduce quenched coordination disorder in lattice models. We simulate the disordered system ... More
Extended versus localized vibrations: the case of L-cysteine and L-cystine amino acidsFeb 28 2014A detailed quantitative analysis of the specific heat in the $1.8-300$ K temperature range for L-cysteine and L-cystine amino acids was presented. We observed not extended but a sharp transition at $\sim 76$ K for L-cysteine. This transition was associated ... More
Multipartite monogamous relations for Entanglement and DiscordFeb 01 2018The distribution of quantum correlations in multipartite systems play a significant role in several aspects of the quantum information theory. While it is well known that these quantum correlations can not be freely distributed, the way that it is shared ... More
Origami-based spintronics in grapheneApr 10 2013Aug 14 2013We show that periodically folded graphene sheets with enhanced spin-orbit interaction due to curvature effects can carry spin polarized currents and have gaps in the electronic spectrum in the presence of weak magnetic fields. Our results indicate that ... More
Analysis of functionally graded material plates using triangular elements with cell-based smoothed discrete shear gap methodJun 20 2013In this paper, a cell based smoothed finite element method with discrete shear gap technique is employed to study the static bending, free vibration, mechanical and thermal buckling behaviour of functionally graded material (FGM) plates. The plate kinematics ... More
Coupling between phonons and magnetic excitations in orthorhombic Eu_{1-x}Y_xMnO_3Mar 27 2009In this work we present a detailed study of the structural and lattice dynamic properties of Y-doped EuMnO3 ceramics (Eu1-xYxMnO3, with 0<x<0.55). A thorough analysis towards the correlation between both structural and Raman modes parameters has been ... More
Cosmic String in the Supersymmetric CSKR TheoryDec 30 2000Apr 16 2002We study a cosmic string solution of an N=1-supersymmetric version of the Cremmer-Scherk-Kalb-Ramond (CSKR) Lagrangian coupled to a vector superfield by means of a topological mass term. The 2-form gauge potential is proposed to couple non-minimally to ... More
Semileptonic D decay into scalar mesons: a QCD sum rule approachMar 23 2002Mar 27 2002Semileptonic decays of D-mesons into scalar hadronic states are investigated. Two extreme cases are considered: a) the meson decays directly into an uncorrelated scalar state of two two mesons and b) the decay proceeds via resonance formation. QCD sum ... More
Non-RKKY oscillations of exchange coupling in magnetic multilayersNov 14 1995It is shown how the exchange coupling between two ferromagnetic planes embedded in an infinite non-magnetic metal, regarded as a function of the distance between the planes, may contain important components which oscillate with periods not predicted by ... More
The Nature and Validity of the RKKY limit of exchange coupling in magnetic trilayersSep 10 1994The effects on the exchange coupling in magnetic trilayers due to the presence of a spin-independent potential well are investigated. It is shown that within the RKKY theory no bias nor extra periods of oscillation associated with the depth of the well ... More
Aggregation in a mixture of Brownian and ballistic wandering particlesApr 10 2006In this paper, we analyze the scaling properties of a model that has as limiting cases the diffusion-limited aggregation (DLA) and the ballistic aggregation (BA) models. This model allows us to control the radial and angular scaling of the patterns, as ... More
Modelling of epitaxial film growth with a Ehrlich-Schwoebel barrier dependent on the step heightJun 30 2011The formation of mounded surfaces in epitaxial growth is attributed to the presence of barriers against interlayer diffusion in the terrace edges, known as Ehrlich-Schwoebel (ES) barriers. We investigate a model for epitaxial growth using a ES barrier ... More
Weak Compactness and Fixed Point Property for Affine Bi-Lipschitz MapsOct 18 2016In this paper we show that if $(y_n)$ is a seminormalized sequence in a Banach space which does not have any weakly convergent subsequence, then it contains a wide-$(s)$ subsequence $(x_n)$ which admits an equivalent convex basic sequence. This fact is ... More
Contact-induced spin polarization in carbon nanotubesNov 28 2003Motivated by the possibility of combining spintronics with molecular structures, we investigate the conditions for the appearance of spin-polarization in low-dimensional tubular systems by contacting them to a magnetic substrate. We derive a set of general ... More
The Lipkin-Meshkov-Glick model with Markovian dissipation -A description of a collective spin on a metallic surfaceJan 02 2018Motivated by recent prototypes of engineered atomic spin devices, we study a fully connected system of n spins 1/2, modeled by the Lipkin-Meshkov-Glick (LMG) model of a collective spin s = n/2 in the presence of Markovian dissipation processes. Employing ... More
Analytical results for long time behavior in anomalous diffusionAug 24 2012We investigate through a Generalized Langevin formalism the phenomenon of anomalous diffusion for asymptotic times, and we generalized the concept of the diffusion exponent. A method is proposed to obtain the diffusion coefficient analytically through ... More
RKKY interaction between extended magnetic defect lines in grapheneJun 03 2014Of fundamental interest in the field of spintronics is the mechanism of indirect exchange coupling between magnetic impurities embedded in metallic hosts. A range of physical features, such as magnetotransport and overall magnetic moment formation, are ... More
Quantum and semiclassical spin networks: from atomic and molecular physics to quantum computing and gravityJan 08 2009The mathematical apparatus of quantum--mechanical angular momentum (re)coupling, developed originally to describe spectroscopic phenomena in atomic, molecular, optical and nuclear physics, is embedded in modern algebraic settings which emphasize the underlying ... More
A computationally efficient method for calculating the maximum conductance of disordered networks: Application to 1-dimensional conductorsFeb 11 2010Aug 06 2010Random networks of carbon nanotubes and metallic nanowires have shown to be very useful in the production of transparent, conducting films. The electronic transport on the film depends considerably on the network properties, and on the inter-wire coupling. ... More