Hermitian Rank and Rigidity of Holomorphic Mappings

Huang's Lemma is an important tool in CR geometry to study rigidity problems. This paper introduces a generalization of Huang's Lemma based on the rigidity properties of holomorphic mappings preserving certain orthogonality on projective spaces, which is optimal for the case of partial linearity. By exploring the intricate relationship between rigidity and Huang's Lemma, we establish that the rigidity properties of Segre maps or proper holomorphic mappings between generalized balls with Levi-degenerate boundaries can be inferred from those between generalized balls with Levi-non-degenerate boundaries by in a coordinate-free and more geometric manner.