Probing the stability of gravastars by dropping dust shells onto them

Merse E Gáspár (1) , István Rácz (1)

1 RMKI

As a preparation for the dynamical investigations, this paper starts by providing a short review of the three-layer gravastar model with distinguished attention to the structure of the pertinent parameter space of gravastars in equilibrium. Then @BULLET the radial stability of these type of gravastars is studied by determining their response @BULLET @BULLET for the totally inelastic collision of their surface layer with a dust shell. It is assumed that dominant energy condition holds and the speed of sound do not exceed that of the light in the matter of the surface layer. While in the analytic setup the equation of state is kept to be generic, in the numerical investigations three functionally distinct class of equation of states are applied. In the corresponding particular cases the maximal mass of the dust shell that may fall onto a gravastar without converting it into a black hole is determined. For those configurations which remain stable the excursion of their radius is assigned. It is found that even the most compact gravastars cannot get beyond the lower limit of the size of conventional stars, provided that the dominant energy condition holds in both cases. It is also shown--independent of any assumption concerning the matter interbridging the internal de Sitter and the external Schwarzschild regions--that the better is a gravastar in mimicing a black hole the easier is to get the system formed by a dust shell and the gravastar beyond itsthe @BULLET @BULLET event horizon of the composite system. In addition, a generic description of the totally @BULLET inelastic collision of spherical shells in spherically symmetric spacetimes is also provided in the appendix.

Mots clés: 04.40.Dg; 97.60.Lf; 04.20.Jb; 95.36.+x

Merse E Gáspár, István Rácz. Probing the stability of gravastars by dropping dust shells onto them. Classical and Quantum Gravity, 2010, 27 (18), pp.185004. ⟨10.1088/0264-9381/27/18/185004⟩. ⟨hal-00625160⟩