Publication date: Nov 2011
Abstract:
Extremely Compact Stars (ECS) contain trapped null geodesics. When such
objects enter the evolution period admitting geodetical motion of
neutrinos, certain part of neutrinos produced in their interior will be
trapped influencing their neutrino luminosity and thermal evolution. We
study neutrino trapping in the braneworld ECS, assuming uniform
distribution of neutrino emissivity and massless neutrinos. We give the
efficiency of the neutrino trapping effects in the framework of the
simple model of the internal spacetime with uniform distribution of
energy density, and external spacetime described by the
Reissner-Nordström geometry characterized by the braneworld "tidal"
parameter b. For b < 0 the external spacetime is of the black-hole
type, while for b > 0 the external spacetime can be of both
black-hole and naked-singularity type. Then the ECS surface radius R can
be located also above the unstable (outer) photon circular orbit. Such
basically new types of the spacetimes strongly alter the trapping
phenomena as compared to the standard case of b = 0. It is shown that
the neutrino trapping effects are slightly lowered by the presence of
physically more plausible case of b < 0, as compared to the standard
internal Schwarzschild spacetime, while they can be magnified by
positive tidal charges if b < 1 and lowered for b > 1. However,
potential astrophysical relevance of the trapping phenomena is strongly
enhanced for negative tidal charges enabling a significant enlargement
of the ECS surface radius to values coherent with recent observations.
Authors:
Stuchlík, Zdeněk; Hladík, Jan; Urbanec, Martin;