Results for "Jefferson F. D. F. Araujo"

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Versatile Hall magnetometer with variable sensitivity assembly for characterization of the magnetic properties of nanoparticlesMay 14 2019Jun 17 2019A Hall magnetometer with variable sensitivity is constructed to measure the magnetic properties of magnetic nanoparticles manufactured by different methods. This novel magnetometer can also be used to measure bulk materials and samples in liquids. The ... More
Versatile Hall magnetometer with variable sensitivity assembly for characterization of the magnetic properties of nanoparticlesMay 14 2019A Hall magnetometer with variable sensitivity is constructed to measure the magnetic properties of magnetic nanoparticles manufactured by different methods. This novel magnetometer can also be used to measure bulk materials and samples in liquids. The ... More
Evaluating the paleomagnetic potential of single zircon crystals using the Bishop TuffMay 26 2016Zircon crystals offer a unique combination of suitability for high-precision radiometric dating and high resistance to alteration. Paleomagnetic experiments on ancient zircons may potentially constrain the earliest geodynamo, which holds broad implications ... More
New method for characterization of magnetic nanoparticles by scanning magnetic microscopyJul 12 2019In this paper, we present a new method for the magnetic characterization of bulk materials, microstructures, and nanostructures. We investigated the magnetic and morphological properties of two colloidal dispersions of iron oxide (Fe3O4) magnetic nanoparticles ... More
Stochastic Background of Gravitational Waves Generated by Compact Binary SystemsApr 23 2015Binary Systems are the most studied sources of gravitational waves. The mechanisms of emission and the behavior of the orbital parameters are well known and can be written in analytic form in several cases. Besides, the strongest indication of the existence ... More
de Sitter invariant special relativity and galaxy rotation curvesJun 17 2017Owing to the existence of an invariant length at the Planck scale, Einstein special relativity breaks down at that scale. A possible solution to this problem is arguably to replace the Poincar\'e-invariant Einstein special relativity by a de Sitter invariant ... More
A New Method to Calculate the Stochastic Background of Gravitational Waves Generated by Compact BinariesApr 16 2015In the study of gravitational waves (GWs), the stochastic background generated by compact binary systems are among the most important kinds of signals. The reason for such an importance has to do with their probable detection by the interferometric detectors ... More
The Gravitational Wave Background From Coalescing Compact Binaries: A New MethodApr 24 2015Gravitational waves are perturbations in the spacetime that propagate at the speed of light. The study of such phenomenon is interesting because many cosmological processes and astrophysical objects, such as binary systems, are potential sources of gravitational ... More
de Sitter-invariant special relativity and the dark energy problemApr 07 2017Apr 13 2017The replacement of the Poincar\'e-invariant Einstein special relativity by a de Sitter-invariant special relativity produces concomitant changes in all relativistic theories, including general relativity. A crucial change in the latter is that both the ... More
Stochastic Background of Gravitational Waves Generated by Eccentric Neutron Star BinariesApr 09 2015Binary systems emit gravitational waves in a well-known pattern; for binaries in circular orbits, the emitted radiation has a frequency that is twice the orbital frequency. Systems in eccentric orbits, however, emit gravitational radiation in the higher ... More
Random perturbations of non-uniformly expanding mapsNov 21 2000We give both sufficient conditions and necessary conditions for the stochastic stability of non-uniformly expanding maps either with or without critical sets. We also show that the number of probability measures describing the statistical asymptotic behaviour ... More
Hyperbolic times: frequency vs. integrabilityNov 25 2003We consider dynamical systems on compact manifolds, which are local diffeomorphisms outside an exceptional set (a compact submanifold). We are interested in analyzing the relation between the integrability (with respect to Lebesgue measure) of the first ... More
Hyperbolic times: frequency versus integrabilityJul 18 2006We consider dynamical systems on compact manifolds, which are local diffeomorphisms outside an exceptional set (a compact submanifold). We are interested in analyzing the relation between the integrability (with respect to Lebesgue measure) of the first ... More
A pedagogical overview about the 2D and 3D Toric Codes and the origin of their topological ordersDec 01 2017In this work, we will show how the topological order of the Toric Code appears when the lattice on which it is defined discretizes a three-dimensional torus. In order to do this, we will present a pedagogical review of the traditional two-dimensional ... More
Comparative study of specific heat measurements in LaMnO3, La1.35Sr1.65Mn2O7, La1.5Sr0.5NiO4 and La1.5Sr0.5CoO4Apr 26 2004We present the temperature dependence of the specific heat, without external magnetic field and with H= 9 T, for LaMnO3, La1.35Sr1.65Mn2O7, La1.5Sr0.5NiO4 and La1.5Sr0.5CoO4 single crystals. We found that spin-wave excitations in the ferromagnetic and ... More
Detailed Far-UV to Optical Analysis of Four [WR] StarsSep 19 2006We present far-UV to optical analyses of four hydrogen deficient central stars of planetary nebulae: BD+303639, NGC 40, NGC 5315 and NGC 6905. Using the radiative transfer code CMFGEN, we determined new physical parameters and chemical abundances for ... More
A Neural Network Architecture for Learning Word-Referent Associations in Multiple ContextsMay 20 2019This article proposes a biologically inspired neurocomputational architecture which learns associations between words and referents in different contexts, considering evidence collected from the literature of Psycholinguistics and Neurolinguistics. The ... More
Effects of Random Biquadratic Couplings in a Spin-1 Spin-Glass ModelMay 01 2000A spin-1 model, appropriated to study the competition between bilinear (J_{ij}S_{i}S_{j}) and biquadratic (K_{ij}S_{i}^{2}S_{j}^{2}) random interactions, both of them with zero mean, is investigated. The interactions are infinite-ranged and the replica ... More
Tricritical Points in the Sherrington-Kirkpatrick Model in the Presence of Discrete Random FieldsMay 22 2000The infinite-range-interaction Ising spin glass is considered in the presence of an external random magnetic field following a trimodal (three-peak) distribution. The model is studied through the replica method and phase diagrams are obtained within the ... More
First-order transitions and triple point on a random p-spin interaction modelApr 28 2000The effects of competing quadrupolar- and spin-glass orderings are investigated on a spin-1 Ising model with infinite-range random $p$-spin interactions. The model is studied through the replica approach and a phase diagram is obtained in the limit $p\to\infty$. ... More
Graviton KK resonant mode in the correction of the Newton's law from 6D braneworldsOct 25 2016In this work, we derive an expression for the correction in the Newton's law of gravitation due to the gravitational Kaluza-Klein states in a general thick string-like braneworld scenario in six dimensions. In order to analyze corrections to Newton's ... More
Graviton KK resonant mode in the correction of the Newton's law from 6D braneworldsOct 25 2016Oct 02 2017In this work, we derive an expression for the correction in the Newton's law of gravitation due to the gravitational Kaluza-Klein states in a general thick string-like braneworld scenario in six dimensions. In order to analyze corrections to Newton's ... More
Dipolar Filtered magic-sandwich-echoes as a tool for probing molecular motions using time domain NMRAug 18 2017We present a simple $^1$H NMR approach for characterizing intermediate to fast regime molecular motions using $^1$H time-domain NMR at low magnetic field. The method is based on a Goldmann Shen dipolar filter (DF) followed by a Mixed Magic Sandwich Echo ... More
On Field Induced Diaelastic Effect in a Small Josephson ContactMar 01 2012An analog of the diaelastic effect is predicted to occur in a small Josephson contact with Josephson vortices manifesting itself as magnetic field induced softening of the contact shear modulus C(T,H). In addition to Fraunhofer type field oscillations, ... More
Magnetic properties of artificially prepared ordered two-dimensional shunted and unshunted Nb-AlO_x-Nb Josephson Junction ArraysNov 09 2005In this Chapter, we present our latest experimental results (along with their theoretical interpretation) related to some unusual magnetic properties of artificially prepared ordered two-dimensional Josephson junction arrays (of both shunted and unshunted ... More
Improving NSGA-II with an Adaptive Mutation OperatorMay 21 2013The performance of a Multiobjective Evolutionary Algorithm (MOEA) is crucially dependent on the parameter setting of the operators. The most desired control of such parameters presents the characteristic of adaptiveness, i.e., the capacity of changing ... More
Magnetic, Structural and cation distribution studies on $FeO \cdot Fe_{(2-x)}Nd_{x}O_{3}$ ($x=0.00, 0.02, 0.04, 0.06 \text{ and } 0.1$) nanoparticlesJul 16 2019We synthesized and characterized the colloidal suspensions of $FeO \cdot Fe_{(2-x)}Nd_{x}O_{3}$ nanoparticles with $x=0.00, 0.02, 0.04, 0.06 \text{ and }0.1.$ The effect of the $Fe^{3+}$ ion replacement by $Nd^{3+}$ on the crystal structure is in-depth ... More
Zero-field spin-splitting and spin lifetime in n-InSb/In1-xAlxSb asymmetric quantum well heterostructuresJan 31 2008Feb 05 2008The spin-orbit (SO) coupling parameters for lowest conduction subband due to structural (SIA) and bulk (BIA) inversion asymmetry are calculated for a range of carrier densities in [001]-grown delta-doped n-type InSb/In1-xAlxSb asymmetric quantum wells ... More
Hydrodynamical Collapse of Neutron Stars due to Hadron-Quark Phase TransitionOct 08 2009We present studies of the collapse of neutron stars that undergo a hadron-quark phase transition. A spherical Lagrangian hydrodynamic code has been written. As initial condition we take different neutron star configurations taking into account its density, ... More
Manifestation of geometric quantization effects in temperature behavior of AC magnetic response of Josephson Junction ArraysJun 16 2005By improving resolution of home-made mutual-inductance measurements technique, a pronounced step-like structure (with the number of steps n=4 for all AC fields) has been observed in the temperature dependence of AC susceptibility in artificially prepared ... More
On the uniform hyperbolicity of some nonuniformly hyperbolic systemsNov 09 2001We give sufficient conditions for the uniform hyperbolicity of certain nonuniformly hyperbolic dynamical systems. In particular, we show that local diffeomorphisms that are nonuniformly expanding on sets of total probability are necessarily uniformly ... More
Acceleration effects on atomic clocksDec 16 2014Jul 27 2015We consider a free massive particle inside a box which is dragged by Rindler observers. Admitting that the particle obeys the Klein-Gordon equation, we find the frequencies of the stationary states of this system. Transitions between the stationary states ... More
The peculiar B-type supergiant HD327083Feb 21 2001Coude spectroscopic data of a poorly-studied peculiar supergiant, HD327083, are presented. Halpha and Hbeta line profiles have been fitted employing a non-LTE code adequate for spherically expanding atmospheres. Line fits lead to estimates of physical ... More
Analog of Fishtail Anomaly in Plastically Deformed GrapheneJul 18 2013By introducing a strain rate generated pseudo-electric field, we discuss a magnetic response of a plastically deformed graphene. Our results demonstrate the appearance of dislocation induced paramagnetic moment in a zero applied magnetic field. More interestingly, ... More
On the origin of unusual transport properties observed in densely packed polycrystalline CaAl_{2}Jan 18 2007A possible origin of unusual temperature behavior of transport coefficients observed in densely packed polycrystalline CaAl_{2} compound [M. Ausloos et al., J. Appl. Phys. 96, 7338 (2004)] is discussed, including a power-like dependence of resistivity ... More
A smoothed string-like braneworld in six dimensionsOct 12 2014We propose here a static and axisymmetric braneworld in six dimensions as a string-like model extension. For a subtle warp function, this scenario provides near brane corrections. By varying the bulk cosmological constant, we obtain a source which passes ... More
Invasion Percolation Between two SitesAug 02 2005We investigate the process of invasion percolation between two sites (injection and extraction sites) separated by a distance r in two-dimensional lattices of size L. Our results for the non-trapping invasion percolation model indicate that the statistics ... More
Warped flavor symmetry predictions for neutrino physicsSep 22 2015A realistic five-dimensional warped scenario with all standard model fields propagating in the bulk is proposed. Mass hierarchies would in principle be accounted for by judicious choices of the bulk mass parameters, while fermion mixing angles are restricted ... More
Suppression of Giant Magnetoresistance by a superconducting contactJan 29 1999We predict that current perpendicular to the plane (CPP) giant magnetoresistance (GMR) in a phase-coherent magnetic multilayer is suppressed when one of the contacts is superconducting. This is a consequence of a superconductivity-induced magneto-resistive ... More
Cosmological constant constraints from observation-derived energy condition bounds and their application to bimetric massive gravityNov 20 2017Among the various possibilities to probe the theory behind the recent accelerated expansion of the universe, the energy conditions (ECs) are of particular interest, since it is possible to confront and constrain the many models, including different theories ... More
Reconstruction of energy conditions from observations and implications for extended theories of gravityJan 14 2018Feb 28 2019The attempt to describe the recent accelerated expansion of the Universe includes different propositions for dark energy models and modified gravity theories. Establish their features in order to discriminate and even rule out part of these models using ... More
A Large-Diameter Hollow-Shaft Cryogenic Motor Based on a Superconducting Magnetic Bearing for Millimeter-Wave PolarimetryJun 19 2017Oct 05 2017In this paper we present the design and measured performance of a novel cryogenic motor based on a superconducting magnetic bearing (SMB). The motor is tailored for use in millimeter-wave half-wave plate (HWP) polarimeters, where a HWP is rapidly rotated ... More
Observational bounds on extended theories of gravity from energy conditionsJan 14 2018The attempt to describe the recent accelerated expansion of the universe includes different propositions for dark energy models and modified gravity theories. Establish their features in order to discriminate and even rule out part of these models using ... More
The Dark Side of Flipped TrinificationOct 18 2017We propose a model which unifies the Left-Right symmetry with the $SU(3)_L$ gauge group, called flipped trinification, and based on the $SU(3)_C\otimes SU(3)_L\otimes SU(3)_R\otimes U(1)_X$ gauge group. The model inherits the interesting features of both ... More
Probing pairing symmetry of Sm_{1.85}Ce_{0.15}CuO_4 via highly-sensitive voltage measurements: Evidence for strong impurity scatteringJan 18 2007Using a highly-sensitive home-made mutual-inductance technique, temperature profiles of the magnetic penetration depth $\lambda (T)$ in the optimally-doped $Sm_{1.85}Ce_{0.15}CuO_4$ thin films have been extracted. The low-temperature behavior of $\lambda ... More
Thermal expansion of Josephson junctions as an elastic response to an effective stress fieldJan 18 2007By introducing a concept of thermal expansion (TE) of a Josephson junction as an elastic response to an effective stress field, we study (both analytically and numerically) the temperature and magnetic field dependence of TE coefficient $\alpha $ in a ... More
Unifying left-right symmetry and 331 electroweak theoriesNov 07 2016Jan 22 2017We propose a realistic theory based on the $\mathrm{SU(3)_c \otimes SU(3)_L \otimes SU(3)_R \otimes U(1)_{X}}$ gauge group which requires the number of families to match the number of colors. In the simplest realization neutrino masses arise from the ... More
Three-family left-right symmetry with low-scale seesaw mechanismNov 14 2016May 17 2017We suggest a new left-right symmetric model implementing a low-scale seesaw mechanism in which quantum consistency requires three families of fermions. The symmetry breaking route to the Standard Model determines the profile of the "next" expected new ... More
Irreversibility line and low-field grain-boundary pinning in electron-doped superconducting thin filmsJan 19 2007AC magnetic susceptibilities of electron-doped Pr_{1.85}Ce_{0.15}CuO_4 (PCCO) and Sm_{1.85}Ce_{0.15}CuO_4 (SCCO) granular thin films have been measured as a function of temperature and magnetic-field strength. Depending on the level of homogeneity of ... More
On the origin of reentrance in 2D Josephson Junction ArraysJun 23 2005Jun 24 2005A comparative study of the magnetic properties of shunted and unshunted two-dimensional Josephson junction arrays (2D-JJA) is presented. Using a single-plaquette approximation of the 2D-JJA model, we were able to successfully fit all our experimental ... More
ZrO$_2$ tapes as an alternative low-cost flexible substrate to artificially nanostructured materialsOct 25 2016We associate tape casting and magnetron sputtering techniques to engineer flexible nanostructures using ZrO$_2$ green tape as substrate. We systematically investigate the structural, magnetic and electrical properties of NiFe/Cr/NiFe trilayer nanostructures, ... More
Newtonian and relativistic polytropesFeb 11 2011The equation of state inside very compact objects like neutron stars is still largely unkown. Even though a lot progress has been made in recent years to develop the so-called realistic equations of state, a lot of insight can be gained by using polytropic ... More
Zero-temperature TAP equations for the Ghatak-Sherrington modelMay 01 2000The zero-temperature TAP equations for the spin-1 Ghatak-Sherrington model are investigated. The spin-glass energy density (ground state) is determined as a function of the anisotropy crystal field $D$ for a large number of spins. This allows us to locate ... More
Realistic $\mathrm{SU(3)_c \otimes SU(3)_L \otimes U(1)_X}$ model with a type II Dirac neutrino seesaw mechanismJun 27 2016Sep 06 2016Here we propose a realistic $\mathrm{SU(3)_c \otimes SU(3)_L \otimes U(1)_X}$ electroweak gauge model with enlarged Higgs sector. The scheme allows for the natural implementation of a type II seesaw mechanism for Dirac neutrinos, while charged lepton ... More
Stochastic stability of diffeomorphisms with dominated splittingApr 07 2004May 10 2007We prove that the statistical properties of random perturbations of a nonuniformly hyperbolic diffeomorphism are described by a finite number of stationary measures. We also give necessary and sufficient conditions for the stochastic stability of such ... More
Landau levels, self-adjoint extensions and Hall conductivity on a coneMay 26 2014In this work we obtain the Landau levels and the Hall conductivity at zero temperature of a two-dimensional electron gas on a conical surface. We investigate the integer quantum Hall effect considering two different approaches. The first one is an extrinsic ... More
Dynamical seesaw mechanism for Dirac neutrinosJan 20 2016So far we have not been able to establish that, as theoretically expected, neutrinos are their own anti-particles. Here we propose a dynamical way to account for the Dirac nature of neutrinos and the smallness of their mass in terms of a new variant of ... More
Mechanical equilibrium of aggregates of dielectric spheresAug 22 2018Dec 02 2018Industrial as well as natural aggregation of fine particles is believed to be associated with electrostatics. Yet like charges repel, so it is unclear how similarly treated particles aggregate. To resolve this apparent contradiction, we analyze conditions ... More
Magnetic and transport properties of electron-doped superconducting thin films: Pairing symmetry, pinning and spin fluctuationsFeb 15 2008In this Chapter we review our latest results on magnetic (AC susceptibility) and transport (resistivity) properties of Pr1.85Ce0.15CuO4 (PCCO) and Sm1.85Ce0.15CuO4 (SCCO) thin films grown by pulsed laser deposition technique. Three main topics of our ... More
Influence of structural disorder on low-temperature behavior of penetration depth in electron-doped high-T_C thin filmsJan 18 2007To probe the influence of structural disorder on low-temperature behavior of magnetic penetration depth in electron-doped high-T_C superconductors, a comparative study of high-quality Pr_{1.85}Ce_{0.15}CuO_4 (PCCO) and Sm_{1.85}Ce_{0.15}CuO_4 (SCCO) thin ... More
Possible manifestation of spin fluctuations in the temperature behavior of resistivity in Sm_{1.85}Ce_{0.15}CuO_4 thin filmsMay 11 2007A pronounced step-like (kink) behavior in the temperature dependence of resistivity $\rho (T)$ is observed in the optimally-doped $Sm_{1.85}Ce_{0.15}CuO_4$ thin films around $T_{sf}=87K$ and attributed to manifestation of strong spin fluctuations induced ... More
Influence of nonuniform critical current density profile on magnetic field behavior of AC susceptibility in 2D Josephson Junction ArraysJun 20 2005Employing mutual-inductance measurements we study the magnetic field dependence of complex AC susceptibility of artificially prepared highly ordered (periodic) two-dimensional Josephson junction arrays of unshunted Nb-AlO_x-Nb junctions. The observed ... More
Meissner state in finite superconducting cylinders with uniform applied magnetic fieldOct 06 1999We study the magnetic response of superconductors in the presence of low values of a uniform applied magnetic field. We report measurements of DC magnetization and AC magnetic susceptibility performed on niobium cylinders of different length-to-radius ... More
Unifying left-right symmetry and 331 electroweak theoriesNov 07 2016We propose a realistic theory based on the $\mathrm{SU(3)_c \otimes SU(3)_L \otimes SU(3)_R \otimes U(1)_{X}}$ gauge group which requires the number of families to match the number of colors. In the simplest realization neutrino masses arise from the ... More
Gravitational wave background from neutron star phase transitionOct 02 2009We study the generation of a stochastic gravitational wave (GW) background produced by a population of neutron stars (NSs) which go over a hadron-quark phase transition in its inner shells. We obtain, for example, that the NS phase transition, in cold ... More
Determining the neutron star equation of state using the narrow-band gravitational wave detector SchenbergOct 11 2006We briefly review the properties of quasi-normal modes of neutron stars and black holes. We analyse the consequences of a possible detection of such modes via the gravitational waves associated with them, especially addressing our study to the Brazilian ... More
Three-family left-right symmetry with low-scale seesaw mechanismNov 14 2016We suggest a new left-right symmetric model implementing a low-scale seesaw mechanism in which quantum consistency requires three families of fermions. The symmetry breaking route to the Standard Model determines the profile of the "next" expected new ... More
Gravitational wave background from neutron star phase transition for a new class of equation of stateOct 09 2009We study the generation of a stochastic gravitational wave (GW) background produced by a population of neutron stars (NSs) which go over a hadron-quark phase transition in its inner shells. We obtain, for example, that the NS phase transition, in cold ... More
String completion of an $\mathrm{SU(3)_c \otimes SU(3)_L \otimes U(1)_X}$ electroweak modelApr 07 2016Sep 06 2016The extended electroweak $\mathrm{SU(3)_c \otimes SU(3)_L \otimes U(1)_X}$ symmetry framework "explaining" the number of fermion families is revisited. While $331$-based schemes can not easily be unified within the conventional field theory sense, we ... More
Hydrogen neutral outflowing disks of B[e] supergiantsFeb 14 2007The [O I] line emission of the LMC B[e] supergiant R126 is modeled with an outflowing disk scenario. We find that hydrogen in the disk must be ionized by less than 0.1%, meaning that the disk material is predominantly neutral. The free-free emission is ... More
Analysis of Maxwell Equations in a Gravitational FieldJun 16 2000In a gravitational field, we analyze the Maxwell equations, the correponding electromagnetic wave and continuity equations. A particular solution for parellel electric and magnetic fields in a gravitational background is presented. These solutions also ... More
On the volume of singular-hyperbolic setsSep 14 2005Sep 11 2006An attractor $\Lambda$ for a 3-vector field $X$ is singular-hyperbolic if all its singularities are hyperbolic and it is partially hyperbolic with volume expanding central direction. We prove that $C^{1+\alpha}$ singular-hyperbolic attractors, for some ... More
Unusual magnetic relaxation behavior in La0.5Ca0.5MnO3 and Nd0.5Sr0.5MnO3Mar 14 2001We have carried out a systematic magnetic relaxation study, measured after applying and switching off a 5 T magnetic field to polycrystalline samples of La0.5Ca0.5MnO3 and Nd0.5Sr0.5MnO3. The long time logarithmic relaxation rate (LTLRR), decreased from ... More
Cobalt Substitution in CuFe$_{2}$O$_{4}$ spinel and its influence on the crystal structure and phononsJan 31 2013In this work nanometric spinel Co${}_{1-x}$Cu${}_{x}$Fe${}_{2}$O${}_{4}$ powders were obtained by polymeric precursors method at several annealing temperatures between 700 and 1200 ${}^\circ$C. The samples were characterized by means of X-ray powder diffraction, ... More
Binding and interlayer force in the near-contact region of two graphite slabs: experiment and theoryNov 22 2013Via a novel experiment, Liu \emph{et al.} [Phys. Rev. B, {\bf 85}, 205418 (2012)] estimated the graphite binding energy, specifically the cleavage energy, an important physical property of bulk graphite. We re-examine the data analysis and note that within ... More
Controlling Non-Markovian Dynamics Using a Light-based Structured EnvironmentSep 04 2018We present the experimental control of Non-Markovian dynamics of open quantum systems simulated with photonic entities. The polarization of light is used as the system, whereas the surrounding environment is represented by light's spatial structure. The ... More
Investigation of domain wall pinning by square anti-notches and its applications in three terminals MRAMMay 11 2019In this work we perform investigations of the competition between domain-wall pinning and attraction by anti-notches and finite device borders. The conditions for optimal geometries, which can attain a stable domain-wall pinning, are presented. This allow ... More
Specific heat at low temperatures and magnetic measurements in Nd0.5Sr0.5MnO3 and R0.5Ca0.5MnO3 (Nd, Sm, Dy and Ho) samplesAug 20 2002We studied the magnetization as a function of temperature and magnetic field in the compounds Nd0.5Sr0.5MnO3, Nd0.5Ca0.5MnO3, Sm0.5Ca0.5MnO3, Dy0.5Ca0.5MnO3 and Ho0.5Ca0.5MnO3. Ferromagnetic, antiferromagnetic and charge ordering transition in our samples ... More
Study of magnetic and specific heat measurements at low temperatures in Nd0.5Sr0.5MnO3 and Nd0.5Ca0.5MnO3May 29 2001The magnetization at low temperatures for Nd0.5Sr0.5MnO3 and Nd0.5Ca0.5MnO3 samples showed a rapid increase with decreasing temperatures, contrary to a La0.5Ca0.5MnO3 sample. Specific heat measurement at low temperatures showed a Schottky-like anomaly ... More
Specific heat and magnetic measurements in Nd0.5Sr0.5MnO3, Nd0.5Ca0.5MnO3 and Ho0.5Ca0.5MnO3 samplesMar 19 2002We studied the magnetization as a function of temperature and magnetic field in the compounds Nd0.5Sr0.5MnO3, Nd0.5Ca0.5MnO3 and Ho0.5Ca0.5MnO3. It allowed us to identify the ferromagnetic, antiferromagnetic and charge ordering phases in each case. The ... More
The Ultraviolet Spectra of the Weak Emission Line Central Stars of Planetary NebulaeOct 03 2007The ultraviolet spectra of all ``weak emission line central stars of planetary nebulae'' (WELS) with available IUE data are presented and discussed. We performed line identifications, equivalent width and flux measurements for several features in their ... More
Spectroscopic analysis of two peculiar emission line stars: RJHA 49 and SS73 21Jul 19 2007Aims: To investigate the spectra and the evolutionary stages of two peculiar emission-line stars: RJHA 49 and SS73 21. Methods: We used low and high resolution optical data. Line identifications and measurements were performed for several features in ... More
Phase locking dynamics of dipolarly coupled vortex-based spin transfer oscillatorsFeb 24 2012Phase locking dynamics of dipolarly coupled vortices excited by spin-polarized current in two identical nanopillars is studied as a function of the interpillar distance L. Numerical study and analytical model have proved the remarkable efficiency of magneto-static ... More
Fabrication and physical properties of stable room temperature bulk ferromagnetic graphiteAug 19 2004The search for macroscopic magnetic ordering phenomena in organic materials, in particular in pure graphite, has been one of the more exciting scientific activities working in the frontiers of physics, chemistry, and materials science. In this Letter ... More
Positive solutions for non-variational fractional elliptic systems with negative exponentsMar 21 2019In this paper, we study strongly coupled elliptic systems in non-variational form with negative exponents involving fractional Laplace operators. We investigate the existence, nonexistence, and uniqueness of the positive classical solution. The results ... More
Optimizing magneto-dipolar interactions for synchronizing vortex based spin-torque nano-oscillatorsJun 05 2015We report on a theoretical study about the magneto-dipolar coupling and synchronization between two vortex-based spin-torque nano-oscillators. In this work we study the dependence of the coupling efficiency on the relative magnetization parameters of ... More
Non-Adlerian synchronization of dipolar coupled vortex Spin-Torque Nano-OscillatorsAug 17 2013We investigate analytically and numerically the synchronization dynamics of dipolarly coupled vortex based Spin-Torque Nano Oscillators (STNO) with different pillar diameters. We identify the critical interpillar distances on which synchronization occurs ... More
Synthesis, characterization and magnetic properties of room-temperature nanofluid ferromagnetic graphiteDec 29 2009We report the chemical synthesis route, structural characterization, and physical properties of nanofluid magnetic graphite (NFMG) obtained from the previously synthesized bulk organic magnetic graphite (MG) by stabilizing the aqueous ferrofluid suspension ... More
Multi-channel S-matrices from energy levels in finite boxesNov 09 2012Mar 06 2013We show that for a generic quantum mechanical system with more than one open scattering channel, it is not possible to fully reconstruct the theory's S-matrix from spectral information obtained in large finite volumes with periodic boundary conditions. ... More
Continuous variables quantum computation over the vibrational modes of a single trapped ionFeb 29 2016Mar 07 2016We consider the quantum processor based on a chain of trapped ions to propose an architecture wherein the motional degrees of freedom of trapped ions (position and momentum) could be exploited as the computational Hilbert space. We adopt a continuous-variables ... More
Continuous variables quantum computation over the vibrational modes of a single trapped ionFeb 29 2016Mar 31 2017We consider the quantum processor based on a chain of trapped ions to propose an architecture wherein the motional degrees of freedom of trapped ions (position and momentum) could be exploited as the computational Hilbert space. We adopt a continuous-variables ... More
Continuous variables quantum computation over the vibrational modes of a single trapped ionFeb 29 2016Nov 19 2016We consider the quantum processor based on a chain of trapped ions to propose an architecture wherein the motional degrees of freedom of trapped ions (position and momentum) could be exploited as the computational Hilbert space. We adopt a continuous-variables ... More
Magnetic remanence of Josephson junction arraysOct 07 1999In this work we study the magnetic remanence exhibited by Josephson junction arrays in response to an excitation with an AC magnetic field. The effect, predicted by numerical simulations to occur in a range of temperatures, is clearly seen in our tridimensional ... More
Manifestation of vortex depinning transition in nonlinear current-voltage characteristics of polycrystalline superconductor Y_{1-x}Pr_{x}Ba_2Cu_3O_7May 28 2008We present our recent results on the temperature dependence of current-voltage characteristics for polycrystalline Y_{1-x}Pr_{x}Ba_2Cu_3O_7 superconductors with x = 0.0, 0.1 and 0.3. The experimental results are found to be reasonably well fitted for ... More
Meissner - London state in superconductors of rectangular cross-section in perpendicular magnetic fieldMar 01 2000The distribution of magnetic induction in Meissner state with finite London penetration depth is analyzed for platelet samples of rectangular cross-section in a perpendicular magnetic field. The exact 2D numerical solution of the London equation is extended ... More
Reentrant AC magnetic susceptibility in Josephson-junction arrays: An alternative explanation for the paramagnetic Meissner effectOct 06 1999The paramagnetic Meissner effect (PME) measured in high $T_{C}$ granular superconductors has been attributed to the presence of $\pi$-junctions between the grains. Here we present measurements of complex AC magnetic susceptibility from two-dimensional ... More
Relativistic Quark Spin Coupling Effects in the Nucleon Electromagnetic Form FactorsNov 03 1999We investigate the effect of different forms of relativistic spin coupling of constituent quarks in the nucleon electromagnetic form factors. The four-dimensional integrations in the two-loop Feynman diagram are reduced to the null-plane, such that the ... More
Towards gauge coupling unification in left-right symmetric $\mathrm{SU(3)_c \times SU(3)_L \times SU(3)_R \times U(1)_{X}}$ theoriesMar 28 2017We consider the possibility of gauge coupling unification within the simplest realizations of the $\mathrm{SU(3)_c \times SU(3)_L \times SU(3)_R \times U(1)_{X}}$ gauge theory. We present a first exploration of the renormalization group equations governing ... More
Application of Renormalization to Potential ScatteringAug 06 1997A recently proposed renormalization scheme can be used to deal with nonrelativistic potential scattering exhibiting ultraviolet divergence in momentum space. A numerical application of this scheme is made in the case of potential scattering with $r^{-2}$ ... More
Manifestation of geometric resonance in current dependence of AC susceptibility for unshunted array of Nb-AlOx-Nb Josephson junctionsAug 24 2010A pronounced resonance-like structure has been observed in the current dependence of AC susceptibility for two-dimensional array of unshunted Nb-AlOx-Nb Josephson junctions. Using a single-plaquette approximation, we were able to successfully fit our ... More