1,305 research outputs found
A group theoretic approach to shear-free radiating stars
A systematic analysis of the junction condition, relating the radial pressure
with the heat flow in a shear-free relativistic radiating star, is undertaken.
This is a highly nonlinear partial differential equation in general. We obtain
the Lie point symmetries that leave the boundary condition invariant. Using a
linear combination of the symmetries, we transform the junction condition into
ordinary differential equations. We present several new exact solutions to the
junction condition. In each case we can identify the exact solution with a Lie
point generator. Some of the solutions obtained satisfy the linear barotropic
equation of state. As a special case we regain conformally flat models which
were found previously. Our analysis highlights the interplay between Lie
algebras, nonlinear differential equations and application to relativistic
astrophysics.Comment: 11 pages, Submitted for publication, minor revision
Lovelock black holes surrounded by quintessence
Lovelock gravity consisting of the dimensionally continued Euler densities is
a natural generalization of general relativity to higher dimensions such that
equations of motion are still second order, and the theory is free of ghosts. A
scalar field with a positive potential that yields an accelerating universe has
been termed quintessence. We present exact black hole solutions in
-dimensional Lovelock gravity surrounded by quintessence matter and also
perform a detailed thermodynamical study. Further, we find that the mass,
entropy, and temperature of the black hole are corrected due to the
quintessence background. In particular, we find that phase transition occurs
with divergence of heat capacity at the critical horizon radius, and that
specific heat becomes positive for allowing the black hole to become
thermodynamically stable.Comment: 15 pages, 3 figures, accepted for publication in EPJ
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