Gravastars must have anisotropic pressures

By C'eline Cattoen, Tristan Faber, Matt Visser. 2005

298 citations recorded by the source corpus.

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.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/0e34753c9098e557a494cbb3815389db0e8303d2

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Citations in the corpus

How to tell a gravastar from a black hole (2007, methodology): “To remove in part the complications produced by the infinites imal shells in the MM model, Cattoen et al [ 10 ] have found that fluid gravastars can be built if the fluid i s confined to a given layer and has there anisotropic pressures.”
Regular Black Holes with Asymptotically Minkowski Cores (2019, background): “[3–7]) regular black holes, but also the Mazur–Mottola gravastars [8–16], and Dymnikova’s models [17–21].”
Gravitational Condensate Stars: An Alternative to Black Holes (2001, unknown): “The necessity of some anisotropic matter at the joining of the interior to exterior geometries was made explicit in [27].”
Phenomenological aspects of black holes beyond general relativity (2018, background): “In other words, this kind of geometry is qualitatively similar to that of a relativistic star, but with a typical radius of the structure R that can be arbitrarily close to rs, hence violating the isotropic-pressure Buchdahl-Bondi bound [49, 50] (let us note in passing that including pressure anisot”
Radial pulsations and stability of anisotropic stars with a quasi-local equation of state (2010, methodology): “One also finds that anisotropy of pressures is present in the so called “exotic solutions” to Einstein equations such as wormholes [2, 3] or gravastars [4, 5].”
Black holes in general relativity (2009, background): “1, which is a signal that you are “close” to forming an apparent/ dynamical/ trapping horizon, unless you are at the very least willing to adopt anisotropic stresses [49].”
Stable dark energy stars (2005, background): “[25], a generalized class of similar gravastar models that exhibit a continuous pressure profile, without the presence of thin shells was analyzed.”