Cosmological models with a variable cosmological term and bulk viscous models

Locally Rotationally Symmetric Bianchi Type I Massive String Cosmological Models with Bulk Viscosity and Decaying Vacuum Energy Density

“…2 1 T   which matches the result as obtained by Beesham [27]. The decelerating parameter q<0 which shows that the model represents accelerating universe.…”

“…In the absence of bulk viscosity, the model is well defined and energy conditions are satisfied. Also for the model (30), the energy density (), the string tension (), the particle density ( p ) are [27]. We have also calculated state finder parameters {r,s} for the model (30).…”

“…The second model represents accelerating and anisotropic space-time. The vacuum energy density 2 1    as obtained by Beesham [27]. We have also calculated state finder parameters {r,s} and these lead to {1,0} in special case.…”

“…The role of viscosity in cosmology has been studied by several authors viz. Pimentel [25], Berman [26], Beesham [27], Arbab [28], Pavon et al [29], Zimdahl [30], Gron [31], Saha [32,33], Singh et al [34], Bali et al [35,36], Mostafapoor and Gron [37].…”

Magnetized Kantowski--Sachs bulk viscous string cosmological models with decaying vacuum energy density $\Lambda (t)$

“…Bulk viscosity is associated with GUT phase transition and string creation. The effect of viscosity on the evolution of cosmological models and the role of viscosity in avoiding the initial big bang singularity have been studied by several authors [35][36][37][38][39].…”