Large-scale inhomogeneities in modified Chaplygin gas cosmologies

Abstract

We extend the homogeneous modified Chaplygin cosmologies to large-scale perturbations by formulating a Zeldovich-like approximation. We show that the model interpolates between an epoch with a soft equation of state and a de Sitter phase, and that in the intermediate regime its matter content is simply the sum of dust and a cosmological constant. We then study how the large-scale inhomogeneities evolve and compare the results with cold dark matter (CDM), $\Lambda$CDM and generalized Chaplygin scenarios. Interestingly, we find that unlike the latter, our models do always resemble $\Lambda$CDM.