Abstract
Gravastars are configurations of compact singularity-free gravitational objects which are interesting alternatives to classical solutions in the strong gravitational field regime. Although there are no static star-like solutions of the Einstein–Klein–Gordon equations for real scalar fields, we show that dynamical gravastars solutions arise through the direct interaction of a scalar field with matter. Two configurations presented here show that, within the internal zone, the scalar field plays a role similar to a cosmological constant, while it decays at large distances as the Yukawa potential. Like classical gravastars, these solutions exhibit small values of the temporal metric component near a transitional radial value, although this behaviour is not determined by the de Sitter nature of the internal space-time, but rather by a slowly-varying scalar field. The scalar field-matter interaction is able to define trapping forces that rigorously confine the polytropic gases to the interior of a sphere. At the surface of these spheres, pressures generated by the field-matter interaction play the role of “walls” preventing the matter from flowing out. These solutions predict a stronger scattering of the accreting matter with respect to Schwarzschild black holes.
Highlights
One of the most attractive alternatives are gravitationalvacuum stars, first proposed in references [6,7,8] as an extension of Bose–Einstein condensates in gravitational systems, and which constitute a broad class of solutions which do not require exotic new physics as they are supported by negative pressure and present no singularities or event horizons
The present work identifies a new type of such solutions, which we call dynamical gravastars because the role of the de Sitter space in repelling matter away from the origin of coordinates is played here by a scalar field, a more dynamical object than the cosmological constant in the de Sitter space
We have found new examples of gravastar-like field configurations in General Relativity which are solutions of the EKG equations including matter. Their existence is allowed by the presence of a direct interaction between the scalar field and matter
Summary
One of the most attractive alternatives are gravitationalvacuum stars (gravastars), first proposed in references [6,7,8] as an extension of Bose–Einstein condensates in gravitational systems, and which constitute a broad class of solutions which do not require exotic new physics as they are supported by negative pressure and present no singularities or event horizons. The interaction between the scalar field and matter is implemented by an assumed proportionality of the energy density ε( p(r )) with the sources of the scalar field J (r ) In this example, the equation coming from the Bianchi identity (which implements the mechanical equilibrium condition for this system) allows for solutions showing a jump-like reduction of the pressure to zero values at some radial point. The solution is close to the Schwarzschild space-time These results argue, for the existence of solutions of the EKG equations for interacting matter and scalar fields, which truly constitute dynamical gravastars alternatives to the classical solutions.
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