Cosmological models with a variable cosmological term and bulk viscous models

Recently, flat variable-$\ensuremath{\Lambda}$ cosmological models have been discussed by Berman. It is shown that these models are equivalent to perfect fluid models with bulk viscosity which have been presented previously. The model of Berman, which is free of particle creation and which is claimed to solve the entropy problem, is shown to be the usual Einstein-de Sitter model. The nonflat variable-$\ensuremath{\Lambda}$ solutions are obtained and their relationship to bulk viscous solutions is elucidated. Exponentially expanding solutions are also derived. The question of the stability of the models is briefly addressed.

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