On the explicit geometry of a certain blowing-up of a smooth quadric

Abstract

Using the high symmetry in the geometry of a smooth projective quadric, we construct effectively new families of smooth projective rational surfaces whose nef divisors are regular, and whose effective monoids are finitely generated by smooth projective rational curves of negative self-intersection. Furthermore, the Cox rings of these surfaces are finitely generated, the dimensions of their anticanonical complete linear systems are zero, and their nonzero nef divisors intersect positively the anticanonical ones. And in two special cases, we give efficient ways of describing any effective divisor class in terms of the given minimal generating sets for the effective monoids of these surfaces. The ground field of our varieties is algebraically closed of arbitrary characteristic.

Keywords

• smooth projective quadric surface
• numerical equivalence
• effective monoid
• minimal model
• infinitely near points
• cox rings
• primary 14c20, 14c22
• secondary 14j26