Little Rip cosmological models with time-dependent equation of state
  Specific dark energy models, leading to the Little Rip (LR) cosmology in the far future, are investigated. Conditions for the occurrence of LR in terms of the parameters present in the proposed equation of state for the dark energy cosmic fluid are studied. Estimates about the time needed before the occurrence of the rip singularity in the standard LR model and the model in which the universe approaches the de Sitter space-time asymptotically, are given. 
I. Brevik, V. V. Obukhov, K. E. Osetrin, and A. V. Timoshkin
gr-qc