On the duality in four-dimensional Lorentz-breaking field theories

We consider new issues of duality in four-dimensional Lorentz-breaking field theories. In particular, we demonstrate that the arising of the aether-like Lorentz-breaking term is necessary in order for the 4D models to display the duality analog between the MCS and self-dual models in 3D. We further study the dispersion relations in both theories and discuss the physical contents of the models involved in this new dualilty.Comment: 16 page

Five-Dimensional QED, Muon Pair Production and Correction to the Coulomb Potential

We consider QED in five dimensions in a configuration where matter is localized on a 3-brane while foton propagates in the bulk. The idea is to investigate the effects of the Kaluza-Klein modes of the photon in the relativistic regime, but in low energy, and in the nonrelativistic regime. In the relativistic regime, we calculate the cross section for the reaction $e^+ + e^- \to \mu^+ + \mu^-$. We compare our theoretical result with a precise measurement of this cross section at $\sqrt{s}=57.77$ GeV. As result, we extract a lower bound on the size of the extra dimension. In the nonrelativistic regime, we derive the contribution for the Coulomb potential due to the whole tower of the Kaluza-Klein excited modes of the photon. We use the modified potential to calculate the Rutherford scattering differential cross section.Comment: minor changes, three new refs. added, to appear in IJMP

Noncommutative fields in three dimensions and mass generation

We apply the noncommutative fields method for gauge theory in three dimensions where the Chern-Simons term is generated in the three-dimensional electrodynamics. Under the same procedure, the Chern-Simons term is shown to be cancelled in the Maxwell-Chern-Simons theory for the appropriate value of the noncommutativity parameter. Hence the mutual interchange between Maxwell-Chern-Simons theory and pure Maxwell theory turns out to be generated within this method.Comment: Comments 5 pages, epl, version accepted for publication in Europhysics Letter

Descrição das larvas das principais espécies de peixes utilizadas pela pesca, no Pantanal.

Elaborou-se uma chave ilustrada, baseando-se na comparacao de caracteristicas morfologicas e morfometricas dos estadios iniciais, quando as larvas ainda sao encontradas no plancton, a deriva no rio. A chave possui a descricao das cinco principais especies utilizadas economicamente no Pantanal: pacu (Piaractus mesopotamicus), curimbata (Prochilodus lineatus), dourado (Salminus maxillosus), piavucu (Leporinus macrocephalus). As especies pintado (Pseudoplatystoma corruscans) e cachara (Pseudoplatystoma fasciatum), por nao apresentarem nenhuma diferenca nas caracteristicas utilizadas nas descricoes, foram incluidas em Pseudoplatystoma sp. As descricoes foram feitas a partir de amostras obtidas em condicoes artificiais.bitstream/item/37433/1/BP19.pd

The Noncommutative Anandan's Quantum Phase

In this work we study the noncommutative nonrelativistic quantum dynamics of a neutral particle, that possesses permanent magnetic and electric dipole momenta, in the presence of an electric and magnetic fields. We use the Foldy-Wouthuysen transformation of the Dirac spinor with a non-minimal coupling to obtain the nonrelativistic limit. In this limit, we will study the noncommutative quantum dynamics and obtain the noncommutative Anandan's geometric phase. We analyze the situation where magnetic dipole moment of the particle is zero and we obtain the noncommutative version of the He-McKellar-Wilkens effect. We demonstrate that this phase in the noncommutative case is a geometric dispersive phase. We also investigate this geometric phase considering the noncommutativity in the phase space and the Anandan's phase is obtained.Comment: 15 pages, revtex4, version to appear in Physical Review

Gauge Invariant Effective Potential for Abelian Maxwell-Chern-Simons Systems

We investigate the effective potential for Abelian Maxwell--Chern--Simons systems. The calculations follow an alternate approach, recently proposed as a gauge invariant formulation of the effective potential, constructed in terms of a gauge invariant order parameter. We compare the results with another investigation, obtained within a standard route of calculating the effective potential.Comment: 10 pages. Revtex. To appear in Phys. Rev.

Uso do método de EBERHART e RUSSELL como informação a priori para aplicação de redes neurais artificiais e análise discriminante visando a classificação de genótipos de alfafa quanto à adaptabilidade e estabilidade fenotípica.

O objetivo deste trabalho foi comparar os resultados obtidos pela metodologia de Eberhart e Russell (1966) com a Análise Discriminante e o treinamento de uma rede neural artificial para análise da adaptabilidade e estabilidade fenotípica de genótipos de alfafa (Medicago sativa). Foram utilizados dados provenientes de um experimento sobre produção de matéria seca de 92 genótipos de alfafa realizado no delineamento em blocos casualizados, com duas repetições. Os genótipos foram submetidos a 20 cortes, no período de novembro de 2004 a junho de 2006. Cada corte foi considerado um ambiente. Diante dos resultados apresentados, verifica-se que a rede neural artificial apresentou índices de concordância mais elevados do que a Análise Discriminante com relação aos resultados obtidos pela metodologia de Eberhart e Russell (1966)