How the Cosmological Constant Affects Gravastar Formation

TL;DR

This paper explores how the cosmological constant influences gravastar formation, revealing conditions under which different compact objects form, including black holes and stable gravastars, with the exterior cosmological constant limiting gravastar development.

Contribution

It extends previous gravastar models by including an external de Sitter-Schwarzschild spacetime and analyzes the impact of the cosmological constant on formation outcomes.

Findings

Exterior cosmological constant must be smaller than interior for gravastar formation

No stable gravastar forms when Schwarzschild mass is zero

Different final states depend on mass, cosmological constants, and shell properties

Abstract

Here we generalized a previous model of gravastar consisted of an internal de Sitter spacetime, a dynamical infinitely thin shell with an equation of state, but now we consider an external de Sitter-Schwarzschild spacetime. We have shown explicitly that the final output can be a black hole, a "bounded excursion" stable gravastar, a stable gravastar, or a de Sitter spacetime, depending on the total mass of the system, the cosmological constants, the equation of state of the thin shell and the initial position of the dynamical shell. We have found that the exterior cosmological constant imposes a limit to the gravastar formation, i.e., the exterior cosmological constant must be smaller than the interior cosmological constant. Besides, we have also shown that, in the particular case where the Schwarzschild mass vanishes, no stable gravastar can be formed, but we still have formation of black hole.