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Gaussian curvature of the two-surface r=0, t=const is calculated for theKerr-de Sitter and Kerr-Newman-de Sitter solutions, yielding non-zeroanalytical expressions for both the cases. The results obtained, on the onehand, exclude the possibility for that surface to be a disk and, on the otherhand, permit one to establish a correct geometrical interpretation of thatsurface for each of the two solutions.

On non-disk geometry of r = 0 in Kerr-de Sitter and Kerr-Newman-de Sitter spacetimes