Interacting spin 0 fields with torsion via Duffin-Kemmer-Petiau theory

Here we study the behaviour of spin 0 sector of the DKP field in spaces with torsion. First we show that in a Riemann-Cartan manifold the DKP field presents an interaction with torsion when minimal coupling is performed, contrary to the behaviour of the KG field, a result that breaks the usual equivalence between the DKP and the KG fields. Next we analyse the case of Teleparallel Equivalent of General Relativity Weitzenbock manifold, showing that in this case there is a perfect agreement between KG and DKP fields. The origins of both results are also discussed.Comment: 10 pages, no figures, uses REVTEX. Changes in the presentation, minor misprints and one equation corrected. References updated. To appear in General Relativity and Gravitatio

Conformal invariance of massless Duffin-Kemmer-Petiau theory in Riemannian space-times

We investigate the conformal invariance of massless Duffin-Kemmer-Petiau theory coupled to riemannian space-times. We show that, as usual, in the minimal coupling procedure only the spin 1 sector of the theory -which corresponds to the electromagnetic field- is conformally invariant. We show also that the conformal invariance of the spin 0 sector can be naturally achieved by introducing a compensating term in the lagrangian. Such a procedure -besides not modifying the spin 1 sector- leads to the well-known conformal coupling between the scalar curvature and the massless Klein-Gordon-Fock field. Going beyond the riemannian spacetimes, we briefly discuss the effects of a nonvanishing torsion in the scalar case.Comment: 8 pages, no figures. Major changes in contend and results. To appear in Class.Quant.Gra

Metodologia científica: cultivo in vitro de unha-de-gato.

O uso da unha-de-gato como produto comercial (fitoterápico) apresenta algumas dificuldades, entre elas a falta de homogeneidade na constituição química das plantas comercializadas. Esse problema ocorre pelo fato da matéria-prima ser proveniente de áreas naturais sem nenhum controle de qualidade. Nesse sentido, a tecnologia de clonagem in vitro, apoiada por um trabalho de seleção de características desejáveis, poderá contribuir para a obtenção de plantas com maior homogeneidade e de qualidade garantida.bitstream/item/99059/1/24058.PD

Hamilton-Jacobi formulation for singular systems with second order lagrangians

Recently the Hamilton-Jacobi formulation for first order constrained systems has been developed. In such formalism the equations of motion are written as total differential equations in many variables. We generalize the Hamilton-Jacobi formulation for singular systems with second order Lagrangians and apply this new formulation to Podolsky electrodynamics, comparing with the results obtained through Dirac's method

Scalar and Spinor Particles in the Spacetime of a Domain Wall in String Theory

We consider scalar and spinor particles in the spacetime of a domain wall in the context of low energy effective string theories, such as the generalized scalar-tensor gravity theories. This class of theories allows for an arbitrary coupling of the wall and the (gravitational) scalar field. First, we derive the metric of a wall in the weak-field approximation and we show that it depends on the wall's surface energy density and on two post-Newtonian parameters. Then, we solve the Klein-Gordon and the Dirac equations in this spacetime. We obtain the spectrum of energy eigenvalues and the current density in the scalar and spinor cases, respectively. We show that these quantities, except in the case of the energy spectrum for a massless spinor particle, depend on the parameters that characterize the scalar-tensor domain wall.Comment: LATEX file, 21 pages, revised version to appear in Phys. Rev.