4,386 research outputs found
Evolution of relativistic polytropes in the post--quasi--static regime
A recently presented method for the study of evolving self-gravitating
relativistic spheres is applied to the description of the evolution of
relativistic polytropes. Two different definitions of relativistic polytrope,
yielding the same Newtonian limit, are considered. Some examples are explicitly
worked out, describing collapsing polytropes and bringing out the differences
between both types of polytropes.Comment: 42 pages, 7 figures; accepted for publication in GR
Heat flow in the postquasistatic approximation
We apply the postquasistatic approximation to study the evolution of
spherically symmetric fluid distributions undergoing dissipation in the form of
radial heat flow. For a model which corresponds to an incompressible fluid
departing from the static equilibrium, it is not possible to go far from the
initial state after the emission of a small amount of energy. Initially
collapsing distributions of matter are not permitted. Emission of energy can be
considered as a mechanism to avoid the collapse. If the distribution collapses
initially and emits one hundredth of the initial mass only the outermost layers
evolve. For a model which corresponds to a highly compressed Fermi gas, only
the outermost shell can evolve with a shorter hydrodynamic time scale.Comment: 5 pages, 5 figure
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