Light radioactive nuclei capture reactions with phenomenological potential models

Light radioactive nuclei play an important role in many astrophysical environments. Due to very low cross sections of some neutron and proton capture reactions by these radioactive nuclei at energies of astrophysical interest, direct laboratory measurements are very difficult. For radioactive nuclei such as 8Li and 8B, the direct measurement of neutron capture reactions is impossible. Indirect methods have been applied to overcome these difficulties. In this work we will report on the results and discussion of phenomenological potential models used to determine some proton and neutron capture reactions. As a test we show the results for the 16O(p,g)17F_gs(5/2+) and 16O(p,g)17F_ex(1/2+) capture reactions.We also computed the nucleosynthesis cross sections for the 7Li(n,g)8Li, 8Li(n,g)9Li and 8B(p,g)9C capture reactions.Comment: Invited talk at Nuclear Physics Meeting in Brazil (2009). To be published at AIP conference proceeding

Dilatonic, Current-Carrying Cosmic String

We study the implications of a scalar-tensorial gravity for the metric of an isolated self-gravitating superconducting cosmic string. These modifications are induced by an arbitrary coupling of a massless scalar field to the usual tensorial field in the gravitational Lagrangian. We derive the metric in the weak-field approximation and we analyse the behaviour of light in this spacetime. We end with some discussions.Comment: 12 pp, Latex, no figures, based on a talk given by M. E. X. Guimaraes at the COSMO 99, 27/9 to 02/10/99, ICTP, Trieste, I

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

Massive photons and Dirac monopoles: electric condensate and magnetic confinement

We use the generalized Julia-Toulouse approach (GJTA) for condensation of topological currents (charges or defects) to argue that massive photons can coexist consistently with Dirac monopoles. The Proca theory is obtained here via GJTA as a low energy effective theory describing an electric condensate and the mass of the vector boson is responsible for generating a Meissner effect which confines the magnetic defects in monopole-antimonopole pairs connected by physical open magnetic vortices described by Dirac brane invariants, instead of Dirac strings.Comment: 6 pages, version accepted for publication in Physics Letters