Electromagnetic structure and weak decay of pseudoscalar mesons in a light-front QCD-inspired model

We study the scaling of the $^3S_1-^1S_0$ meson mass splitting and the pseudoscalar weak decay constants with the mass of the meson, as seen in the available experimental data. We use an effective light-front QCD-inspired dynamical model regulated at short-distances to describe the valence component of the pseudoscalar mesons. The experimentally known values of the mass splittings, decay constants (from global lattice-QCD averages) and the pion charge form factor up to 4 [GeV/c]$^2$ are reasonably described by the modelComment: 27 Pages, 7 eps figures,use revtex

Weak decay constant of pseudscalar meson in a QCD-inspired model

We show that a linear scaling between the weak decay constants of pseudoscalar and the vector mesons masses is supported by the available experimental data. The decay constant scale as $f_m/f_{pi}=M_V/M_{\rho}$ (f_m is decay constant and M_V vector meson ground state mass). This simple form is justified within a renormalized light-front QCD-inpired model for quark-antiquark bound states.Comment: 4 pages, use revtex style. To appear "Brazilian Journal of Physics (2003)

Absence of classical and quantum mixing

It is shown, under mild assumptions, that classical degrees of freedom dynamically coupled to quantum ones do not inherit their quantum fluctuations. It is further shown that, if the assumptions are strengthen by imposing the existence of a canonical structure, only purely classical or purely quantum dynamics are allowed.Comment: REVTeX, 4 page

Correspondence between Electro-Magnetic Field and other Dark Energies in Non-linear Electrodynamics

In this work, we have considered the flat FRW model of the universe filled with electro-magnetic field. First, the Maxwell's electro-magnetic field in linear form has been discussed and after that the modified Lagrangian in non-linear form for accelerated universe has been considered. The corresponding energy density and pressure for non-linear electro-magnetic field have been calculated. We have found the condition such that the electro-magnetic field generates dark energy. The correspondence between the electro-magnetic field and the other dark energy candidates namely tachyonic field, DBI-essence, Chaplygin gas, hessence dark energy, k-essenece and dilaton dark energy have been investigated. We have also reconstructed the potential functions and the scalar fields in this scenario.Comment: 11 pages, 7 figure

Planejação de unidades de aprendizagem - CTS: a narrativa como potência do ser professor e da formação

Apresenta-se a narrativa de um processo educativo em um curso de pós-graduação que teve como objetivo a planejação (planejar, desenvolver, narrar, reformular) e crítica de Unidades de Aprendizagem (UA) em uma perspectiva CTS a fim de articular Educação em Ciências e Educação Ambiental. O processo teve duração de um semestre letivo com um grupo de 15 alunos, professores de Ciências em exercício. As UA foram narradas em um Ambiente Virtual de Aprendizagem (AVA). Defende-se o argumento da potencialidade da narrativa como ferramenta de transformação do professor, da escola e da formação de professores. O argumento constrói-se pela diversidade de temáticas, justificativas, objetivos e atividades configurados e refigurados pelos participantes. Os fragmentos das UA sinalizam para a transformação potencializada nos professores e na sala de aula tanto da formação de professores quanto da escola

Planejação de unidades de aprendizagem - CTS : a narrativa como potência do ser professor e da formação

Apresenta-se a narrativa de um processo educativo em um curso de pós-graduação que teve como objetivo a planejação (planejar, desenvolver, narrar, reformular) e crítica de Unidades de Aprendizagem (UA) em uma perspectiva CTS a fim de articular Educação em Ciências e Educação Ambiental. O processo teve duração de um semestre letivo com um grupo de 15 alunos, professores de Ciências em exercício. As UA foram narradas em um Ambiente Virtual de Aprendizagem (AVA). Defende-se o argumento da potencialidade da narrativa como ferramenta de transformação do professor, da escola e da formação de professores. O argumento constrói-se pela diversidade de temáticas, justificativas, objetivos e atividades configurados e refigurados pelos participantes. Os fragmentos das UA sinalizam para a transformação potencializada nos professores e na sala de aula tanto da formação de professores quanto da escola

Entropy, diffusivity and the energy landscape of a water-like fluid

Molecular dynamics simulations and instantaneous normal mode (INM) analysis of a fluid with core-softened pair interactions and water-like liquid-state anomalies are performed to obtain an understanding of the relationship between thermodynamics, transport properties and the poten- tial energy landscape. Rosenfeld-scaling of diffusivities with the thermodynamic excess and pair correlation entropy is demonstrated for this model. The INM spectra are shown to carry infor- mation about the dynamical consequences of the interplay between length scales characteristic of anomalous fluids, such as bimodality of the real and imaginary branches of the frequency distribu- tion. The INM spectral information is used to partition the liquid entropy into two contributions associated with the real and imaginary frequency modes; only the entropy contribution from the imaginary branch captures the non-monotonic behaviour of the excess entropy and diffusivity in the anomalous regime of the fluid

Dark Matter Subhalos in the Ursa Minor Dwarf Galaxy

Through numerical simulations, we study the dissolution timescale of the Ursa Minor cold stellar clump, due to the combination of phase-mixing and gravitational encounters with compact dark substructures in the halo of Ursa Minor. We compare two scenarios; one where the dark halo is made up by a smooth mass distribution of light particles and one where the halo contains 10% of its mass in the form of substructures (subhalos). In a smooth halo, the stellar clump survives for a Hubble time provided that the dark matter halo has a big core. In contrast, when the point-mass dark substructures are added, the clump survives barely for \sim 1.5 Gyr. These results suggest a strong test to the \Lambda-cold dark matter scenario at dwarf galaxy scale.Comment: accepted for publication in Ap

Impediments to mixing classical and quantum dynamics

The dynamics of systems composed of a classical sector plus a quantum sector is studied. We show that, even in the simplest cases, (i) the existence of a consistent canonical description for such mixed systems is incompatible with very basic requirements related to the time evolution of the two sectors when they are decoupled. (ii) The classical sector cannot inherit quantum fluctuations from the quantum sector. And, (iii) a coupling among the two sectors is incompatible with the requirement of physical positivity of the theory, i.e., there would be positive observables with a non positive expectation value.Comment: RevTex, 21 pages. Title slightly modified and summary section adde