Abstract:
Let f : M 2n → R2n+p, 2 ≤ p ≤ n − 1, be an isometric immersion of a Kaehler manifold into Euclidean space. Yan and Zheng conjectured in [16] that if the codimension is p ≤ 11 then, along any connected component of an open dense subset of M 2n, the submanifold is as follows: it is either foliated by holomorphic submanifolds of dimension at least 2n − 2p with tangent spaces in the kernel of the second fundamental form whose images are open subsets of affine vector subspaces, or it is embedded holomorphically in a Kaehler submanifold of R2n+p of larger dimension than 2n. This bold conjecture was proved by Dajczer and Gromoll just for codimension three and then by Yan and Zheng for codimension
four.
In this paper we prove that the second fundamental form of the submanifold behaves pointwise as expected in case that the conjecture is true. This result is a first fundamental step for a possible classification of the non-holomorphic Kaehler submanifolds lying with low codimension in Euclidean space. A counterexam- ple shows that our proof does not work for higher codimension, indicating that
proposing p = 11 in the conjecture as the largest codimension is appropriate.
