Comment on "Shear-free barotropic perfect fluids cannot rotate and expand simultaneously" by R. Goswami and G.F.R. Ellis

Abstract

We point out an error in a recent paper by Goswami and Ellis. As a consequence the question of whether shear-free barotropic perfect fluids (with $p+\mu \ne 0$) can or cannot rotate and expand simultaneously, is still wide open

3 pages