Re-derivation of the constant-density star in isotropic coordinates produces a transparent metric and highlights under-appreciated special cases including pressure gravitating alone and naked singularities.
Gravastars must have anisotropic pressures
3 Pith papers cite this work. Polarity classification is still indexing.
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abstract
One of the very small number of serious alternatives to the usual concept of an astrophysical black hole is the "gravastar" model developed by Mazur and Mottola; and a related phase-transition model due to Laughlin et al. We consider a generalized class of similar models that exhibit continuous pressure -- without the presence of infinitesimally thin shells. By considering the usual TOV equation for static solutions with negative central pressure, we find that gravastars cannot be perfect fluids -- anisotropic pressures in the "crust" of a gravastar-like object are unavoidable. The anisotropic TOV equation can then be used to bound the pressure anisotropy. The transverse stresses that support a gravastar permit a higher compactness than is given by the Buchdahl--Bondi bound for perfect fluid stars. Finally we comment on the qualitative features of the equation of state that gravastar material must have if it is to do the desired job of preventing horizon formation.
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Current and future observations can test whether dark compact objects are Kerr black holes or exotic alternatives, with null results strengthening the black hole paradigm.
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Revisiting Schwarzschild's constant density star in isotropic coordinates
Re-derivation of the constant-density star in isotropic coordinates produces a transparent metric and highlights under-appreciated special cases including pressure gravitating alone and naked singularities.
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Testing the nature of dark compact objects: a status report
Current and future observations can test whether dark compact objects are Kerr black holes or exotic alternatives, with null results strengthening the black hole paradigm.
- Energy conditions in static, spherically symmetric spacetimes and effective geometries