8,235 research outputs found
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
- …