Totally geodesic submanifolds of the exceptional Riemannian symmetric spaces of rank 2

The present article is the final part of a series on the classification of the totally geodesic submanifolds of the irreducible Riemannian symmetric spaces of rank 2. After this problem has been solved for the 2-Grassmannians in my papers [K1] and [K2], and for the space SU(3)/SO(3) in Section 6 of [K3], we now solve the classification for the remaining irreducible Riemannian symmetric spaces of rank 2 and compact type: SU(6)/Sp(3) , SO(10)/U(5) , E6/(U(1) · Spin(10)) , E6/F4 , G2/SO(4) , SU(3) , Sp(2) and G2 . Similarly as for the spaces already investigated in the earlier papers, it turns out that for many of the spaces investigated here, the earlier classification of the maximal totally geodesic submanifolds of Riemannian symmetric spaces by Chen and Nagano ([CN], §9) is incomplete. In particular, in the spaces Sp(2) , G2/SO(4) and G2 , there exist maximal totally geodesic submanifolds, isometric to 2or 3-dimensional spheres, which have a “skew” position in the ambient space in the sense that their geodesic diameter is strictly larger than the geodesic diameter of the ambient space. They are all missing from [CN]. Author’s address. Sebastian Klein Department of Mathematics University College Cork Cork Ireland [email protected]