Classification of Incidence Scrolls (II)

Abstract

The aim of this paper is to obtain a classification of the scrolls in Pn which are defined by a one-dimensional family of lines meeting a certain set of linear spaces in Pn, a first classification for genus 0 and 1 is given in paper [1]. These ruled surfaces are called incidence scrolls, and such an indicated set is a base of the incidence scroll. In particular, we compute its degree and genus. For this, we define the fundamental incidence scroll to be the scroll in Pn formed by the lines which meet (2n-3) P{n-2}'s in general position. Then all the others incidence scrolls will be portions of degenerate forms of this. In this way, we can obtain all the incidence scrolls in Pn, n>2, with base in general position.