Moduli of stable 2-bundles with \(\Delta=-5\) on a nonsingular cubic surface (Q1346792)

The author studies stable 2-bundles with \(c_ 1^ 2 - 4c_ 2 = - 5\) on a smooth cubic surface \(S\) and construct fine moduli spaces. Twisting by line bundles, one reduces to the case where \(c_ 1\) is the class of a \((-1)\)-curve \(E\) and \(c_ 2 = 1\), or \(c_ 1\) is the hyperplane class and \(c_ 2 = 2\). The moduli space of bundles of the former type is obtained from \(S\) by contracting \(E\) to a point. The moduli space of the latter case is isomorphic to \(S\) itself. -- In both cases universal families are constructed.