Weak del Pezzo surfaces with irregularity
Algebraic Geometry
2007-05-23 v2
Abstract
I construct normal del Pezzo surfaces, and regular weak del Pezzo surfaces as well, with positive irregularity q>0. Such things can happen only over nonperfect fields. The surfaces in question are twisted forms of nonnormal del Pezzo surfaces, which were classified by Reid. The twisting is with respect to the flat topology and infinitesimal group scheme actions. The twisted surfaces appear as generic fibers for Fano--Mori contractions on certain threefolds with only canonical singularities.
Cite
@article{arxiv.math/0512153,
title = {Weak del Pezzo surfaces with irregularity},
author = {Stefan Schroeer},
journal= {arXiv preprint arXiv:math/0512153},
year = {2007}
}
Comments
32 pages, minor changes, to appear in Tohoku Math. J