A weaker rigidity theorem for pairs of hyperquadrics and its application

Abstract: In this short article, we establish a rigidity theorem for pairs of hyperquadrics in a weaker sense, i.e., we impose a condition that minimal rational curves are preserved, which is stronger than inheriting a sub-VMRT structure, a notion raised by Mok & Zhang (2014). This problem has its source in a theorem of Tsai (1993), and the main result of this article can be applied back to give a more intrinsic proof of Tsai's theorem.