Perturbations with bulk viscosity in modified chaplygin gas cosmology

Résumé

In this work, we investigate cosmological perturbations of viscous modified chaplygin gas model. Using [Formula: see text] covariant formalism, we define covariant and gauge invariant gradient variables, which after the application of scalar decomposition and harmonic decomposition techniques together with redshift transformation method, provide the energy overdensity perturbation equations in redshift space, responsible for large-scale structure formation. In order to analyze the effect of the viscous modified chaplygin gas model on matter overdensity contrast, we numerically solve the perturbation equations in both long and short wavelength limits. The numerical results show that the energy overdensity contrast decays with redshift. However, the perturbations which include amplitude effects due to the viscous modified chaplygin model do differ remarkably from those in the [Formula: see text]CDM. In the absence of viscous modified chaplygin model, the results reduce to those of [Formula: see text]CDM.

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