Large scale structure and the generalized Chaplygin gas as dark energy

The growth of large scale structure is studied in a universe containing both cold dark matter (CDM) and a generalized Chaplygin gas (GCG). The GCG is assumed to contribute only to the background evolution of the universe, while the CDM component collapses and forms structures. We present some new analytical as well as numerical results for linear and nonlinear growth in such a model. The model passes the standard cosmological distance test without the need of a cosmological constant. But we find that the scenario is severely constrained by current observations of large scale structure. Any small deviations of the GCG parameters away from the standard Lambda dominated cosmology produces substantial suppression for the growth of structures.