Biduality and Reflexivity in Positive Characteristic

Abstract

The biduality and reflexivity theorems are known to hold for projective varieties defined over fields of characteristic zero, and to fail in positive characteristic. In this article, we construct a notion of reflexivity and biduality in positive characteristic by generalizing the ordinary tangent space to the notion of $h$-tangent spaces. The ordinary reflexivity theory can be recovered as the special case $h=0$, of our theory. Several varieties that are not ordinary reflexive or bidual become reflexive in our extended theory.