Stationary states of fermions in a sign potential with a mixed vector-scalar coupling

The scattering of a fermion in the background of a sign potential is considered with a general mixing of vector and scalar Lorentz structures with the scalar coupling stronger than or equal to the vector coupling under the Sturm-Liouville perspective. When the vector coupling and the scalar coupling have different magnitudes, an isolated solution shows that the fermion under a strong potential can be trapped in a highly localized region without manifestation of Klein's paradox. It is also shown that the lonely bound-state solution disappears asymptotically as one approaches the conditions for the realization of spin and pseudospin symmetries.Comment: 4 figure

Scattering and bound states of fermions in a mixed vector-scalar smooth step potential

The scattering of a fermion in the background of a smooth step potential is considered with a general mixing of vector and scalar Lorentz structures with the scalar coupling stronger than or equal to the vector coupling. Charge-conjugation and chiral-conjugation transformations are discussed and it is shown that a finite set of intrinsically relativistic bound-state solutions appears as poles of the transmission amplitude. It is also shown that those bound solutions disappear asymptotically as one approaches the conditions for the realization of the so-called spin and pseudospin symmetries in a four-dimensional space-time.Comment: 5 figures. arXiv admin note: substantial text overlap with arXiv:1310.847

Absence of Gluonic Components in Axial and Tensor Mesons

A quarkonium-gluonium mixing scheme previously developed to describe the characteristic of the pseudoscalar mesons is applied to axial and tensor mesons. The parameters of the model are determined by fitting the eigenvalues of a mass matrix. The corresponding eigenvectors give the proportion of light quarks, strange quarks and glueball in each meson. However the predictions of the model for branching ratios and electromagnetic decays are incompatible with the experimental results. These results suggest the absence of gluonic components in the states of axial and tensor isosinglet mesons analyzed here.Comment: 12 page

Comment on ``Kepler problem in Dirac theory for a particle with position-dependent mass''

Based on easy-to-follow considerations it is not difficult to be vehemently opposed not only the solutions found in that paper but also the conclusions manifested there.Comment: 4 page

Spin and Pseudospin symmetries in the Dirac equation with central Coulomb potentials

We analyze in detail the analytical solutions of the Dirac equation with scalar S and vector V Coulomb radial potentials near the limit of spin and pseudospin symmetries, i.e., when those potentials have the same magnitude and either the same sign or opposite signs, respectively. By performing an expansion of the relevant coefficients we also assess the perturbative nature of both symmetries and their relations the (pseudo)spin-orbit coupling. The former analysis is made for both positive and negative energy solutions and we reproduce the relations between spin and pseudospin symmetries found before for nuclear mean-field potentials. We discuss the node structure of the radial functions and the quantum numbers of the solutions when there is spin or pseudospin symmetry, which we find to be similar to the well-known solutions of hydrogenic atoms.Comment: 9 pages, 2 figures, uses revte

Como promover a fixacao de pesquisadores da Embrapa nos centros de pesquisas da Amazonia Ocidental.

Relata estudo realizado junto aos pesquisadores da Embrapa que trabalham em Unidades Descentralizadas localizadas na Amazônia Ocidental (Amazonas, Rondônia, Roraima, Amapá e Acre). Trabalho executado como prática do Curso de Administração em Ciência e Tecnologia ministrado pela Faculdade de Economia e Administração da USP. Coleta e tabulação dos dados foi realizada no período de julho a novembro/1993. Fez-se levantamento onde foram colhidas através de questionário apropriado, opinião de 60 pesquisadores, num universo de 128 pesquisadores que trabalham nessas Unidades. Procurou-se identificar razões de satisfação e insafisfação desses profissionais para o desenvolvimento de suas atividades, e dessa forma, ter uma percepção das razões da elevada taxa de evasão de pesquisadores que trabalham nas Unidades da Amazônia Ocidental.bitstream/item/58852/1/DOC-1838-0001.pdf(mimeografado)

Limitações do uso dos solos do Estado do Paraná por suscetibilidade à erosão.

bitstream/item/62873/1/CNPS-DOC.-8-84.pdfacompanha mapa color. escala 1:600.000

Bound states of bosons and fermions in a mixed vector-scalar coupling with unequal shapes for the potentials

The Klein-Gordon and the Dirac equations with vector and scalar potentials are investigated under a more general condition, $V_{v}+V_{s}= \mathrm{constant}$. These intrinsically relativistic and isospectral problems are solved in a case of squared hyperbolic potential functions and bound states for either particles or antiparticles are found. The eigenvalues and eigenfuntions are discussed in some detail and the effective Compton wavelength is revealed to be an important physical quantity. It is revealed that a boson is better localized than a fermion when they have the same mass and are subjected to the same potentials.Comment: 3 figure