Slow Rotational Perturbations of Friedmann Universes

In this work the rotational perturbations of the Friedmann universes are investigated. In the general case where none of the terms including Ω(r, t) are neglected, for perfect fluid, the field equations belonging to the perturbed metric give Ω=Ω(t). In this case, since the condition Ω=0 can be accomplished by a coordinate transformation, the solutions of the field equations reduce to those of the classical Friedmann equations. For this reason, the approximate solutions obtained by other authors become formal solutions without physical interest.