  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 the scalar field 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.

General Relativity and Quantum Cosmology;Astrophysics of Galaxies;High Energy Physics - Theory