Finalizing the classification of type II or more special Einstein spacetimes in five dimensions

Abstract

Einstein spacetimes in 5d that are of genuine type II in the null alignment classification are considered. It is shown that the unique geodesic multiple Weyl aligned null direction (mWAND) cannot have an optical matrix of rank 1 or 3. This finalizes the classification of all type II or more special Einstein spacetimes in 5d (i.e., those allowing for an mWAND), and also proves that they all satisfy the so-called optical constraint.