We study the implications on both background and perturbation evolution of introducing a Chaplygin gas component in the universe’s ingredients. We perform likelihood analyses using wide-ranging, SN1a, CMB and large scale structure observations to assess whether such a component could be a genuine alternative to a cosmological constant, $\Lambda .$ We find that the current data favors behavior in an adiabatic Chaplygin gas that is akin to a cosmological constant.

• Received 20 January 2003

DOI:https://doi.org/10.1103/PhysRevD.68.023515