On 3-linear varieties of codimension 2

Abstract

A projective variety in a projective space is said to he p-linear if it is p-regular and has no defining equation of degree < p. It is well known that 2-linear varieties are exactly varieties of minimal degree. In this paper, we study 3-linear varieties of codimension 2. We classify all smooth 3-linear varieties of codimension 2. There are six kinds of such varieties. Also, we provide some nonconic singular 3-linear varieties of codimension 2.