Self-gravitating clouds of generalized Chaplygin and modified anti-Chaplygin gases

Abstract

The Chaplygin gas has been proposed as a possible dark energy, dark matter candidate. As a working fluid in a Friedmann–Robertson–Walker universe, it exhibits early behavior reminiscent of dark matter, but at later times it is more akin to a cosmological constant. In any such universe, however, one can expect local perturbations to form. Here, we obtain the general equations for a self-gravitating relativistic Chaplygin gas. We solve these equations and obtain the mass–radius relationship for such structures, showing that only in the phantom regime is the mass–radius relationship large enough to be a serious candidate for highly compact massive objects at the galaxy core. In addition, we study the cosmology of a modified anti-Chaplygin gas. A self-gravitating cloud of this matter is an exact solution to Einstein's equations.