ADDENDUM TO: MAXIMAL TORI OF EXTRINSIC SYMMETRIC SPACES AND MERIDIANS

Jost-Hinrich Eschenburg, Peter Quast, Makiko Sumi Tanaka
Improving a theorem in [1] we observe that a maximal torus of an extrinsic symmetric space in a euclidean space V is itself extrinsic symmetric in some affine subspace of V. A compact extrinsic symmetric space is a submanifold X ⊂ S p−1 ⊂ R p = V such that for any point x ∈ X the reflection s x along the normal space N = N x X keeps X invariant. Every compact symmetric space X contains a maximal torus T which is unique up to congruence. If X = S n ⊂ R n+1 , the maximal torus is a great circle C
more » ... = X ∩ R 2 which is reflective, hence extrinsic symmetric, see [1, Theorem 4]. But for most extrinsic symmetric spaces, the maximal torus is not reflective. However, as we will show, it is an "iterated" reflective subspace, and in particular:
doi:10.18910/86337 fatcat:lrwqaiaiq5cf7kdxkjxj5wso2y