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;