On the classification of elliptic surfaces with q=1.
In this Note we study certain natural subsets of the cohomological stratification of the moduli spaces of rank vector bundles on an algebraic surface. In the last section we consider the following problem: take a bundle given by an extension, how can one recognize that is a certain given bundle? The most interesting case considered here is the case since it applies to the study of codimension meromorphic foliations with singularities on .
We deal with a reducible projective surface with so-called Zappatic singularities, which are a generalization of normal crossings. First we compute the -genus of , i.e. the dimension of the vector space of global sections of the dualizing sheaf . Then we prove that, when is smoothable, i.e. when is the central fibre of a flat family parametrized by a disc, with smooth general fibre, then the -genus of the fibres of is constant.
Roughly speaking, by using the semi-stable minimal model program, we prove that the moduli part of an lc-trivial fibration coincides with that of a klt-trivial fibration induced by adjunction after taking a suitable generically finite cover. As an application, we obtain that the moduli part of an lc-trivial fibration is b-nef and abundant by Ambro’s result on klt-trivial fibrations.