| Abstract: | A-manifolds and B-manifolds, introduced by Gray(1978), are two significant classes of Einstein-like Riemannian manifolds. A Riemannian manifold is Ricci parallel if and only if it is simultaneously an A-manifold and a B-manifold. The present paper proves that both focal submanifolds of each isoparametric hypersurface in unit spheres with g = 4 distinct principal curvatures are A-manifolds. As for the focal submanifolds with g = 6,m = 1 or 2, only one is an A-manifold, and neither is a B-manifold. |
