Classification of (1, 2)-Grassmann secant defective threefolds
Luca Chiantini, Filip Cools ยท Forum Mathematicum ยท 2010
Abstract In this paper, we classify all smooth threefolds , for which the Grassmann secant variety G 1,2 ( X ) โ ๐พ(1, N ) (i.e. the closure of the set of lines contained in the span of 3 independent points of X ) has not the expected dimension.