Chaplygin gas emerging from an effective description of inhomogeneous universe models

In the framework of spatially averaged inhomogeneous cosmologies in classical general relativity, effective Einstein equations govern the dynamics of averaged scalar variables in a scale–dependent way. A particular cosmology may be characterized by a cosmic equation of state, closing the hierarchy of effective equations. In this context a natural candidate is provided by the Chaplygin gas, standing for a unified description of Dark Energy and Dark Matter. In this paper we reconstruct the inhomogeneous properties of matter and geometry that correspond to the Chaplygin equation of state. The most extreme interpretation assumes that both Dark Energy and Dark Matter are not included as additional sources, but are supposed to be manifestations of spatial geometrical properties. We discuss the consequences of the resulting scenario for effective cosmological parameters. PACS numbers: 04.20.-q, 04.40.-b, 95.35.+d, 95.36.+x, 98.80.-Es, 98.80.-Jk