LRS Bianchi type I stiff fluid inflationary universe with variable bulk viscosity

Abstract

Stiff fluid inflationary cosmological model with variable bulk viscosity in the frame work of locally rotationally symmetric (LRS) Bianchi type I space–time, is investigated. To get the deterministic solution, we have also assumed that σ is proportional to θ and ζθ = constant = α where σ is shear, θ the expansion, and ζ the coefficient of bulk viscosity. The ansatz ζθ = constant, was found to connect with the occurrence of Little Rip cosmology using Friedmann–Robertson–Walker metric given by Brevik et al. (Phys. Rev. D, 84, 103508 (2011)). We find that the model has constant expansion but represents accelerating phase. The model in general represents an anisotropic universe but in special case, it leads to an isotropic one. The spatial volume increases exponentially with time representing the inflationary scenario. The presence of bulk viscosity tends to increase the inflationary phase. Also, the model leads to the de Sitter model in a special case. The presence of bulk viscosity prevents the matter density to vanish at late time. The energy conditions as given by Kolassis et al. (Classical Quantum Gravity, 5, 1129 (1988)). Chatterjee and Banerjee (Gen. Relativ. Gravitation, 36, 303 (2004)) are also discussed. We find that the energy conditions are satisfied for stiff fluid inflationary universe with variable bulk viscosity.