1202.3864 (Amare Abebe et al.)

Simultaneous expansion and rotation of shear-free universes in modified
gravity    [PDF]

Amare Abebe, Rituparno Goswami, Peter K. S. Dunsby

We show in a fully covariant way that, there exist a class of $f(R)$ models
for which a shear-free, almost FLRW universe can expand and rotate at the same
time .

View original: http://arxiv.org/abs/1202.3864