In this paper it has been shown that the neutrino bulk viscous stresses can give rise to the late time acceleration of the universe. It is found that a number of spatially flat FRW models with a negative deceleration parameter can be constructed using neutrino viscosity and one of them mimics a ΛCDM model. This does not require any exotic dark energy component or any modification of gravity.
@article{arxiv.0806.3666,
title = {Can neutrino viscosity drive the late time cosmic acceleration?},
author = {Sudipta Das and Narayan Banerjee},
journal= {arXiv preprint arXiv:0806.3666},
year = {2015}
}