On mm-quasi-Einstein spacetimes
Abstract
In this paper, we have studied mm-quasi-Einstein spacetimes. Some basic results of such spacetimes are derived. Perfect and viscous fluid mm-quasi-Einstein spacetimes are also studied and the expressions of pressure, cosmological constant and energy density are obtained. We have proved that if the generator ρρ of an mm-quasi-Einstein spacetime is a Killing vector field, then the spacetime is either conformally flat or of Petrov-type NN. It is also shown that if the function ff of an mm-quasi-Einstein spacetime satisfying Einstein’s equation is harmonic and the matter distribution is perfect fluid, then Segre’ characteristics of the Ricci tensor is [(1,1), 1]. Finally, an example is constructed for the proper existence of such a spacetime.