Even sets of ($-4$)-curves on rational surface

Abstract

We study rational surfaces having an even set of disjoint ($-4$)-curves. The properties of the surface $S$ obtained by considering the double cover branched on the even set are studied. It is shown, that contrarily to what happens for even sets of ($-2$)-curves, the number of curves in an even set of ($-4$)-curves is bounded (less or equal to 12). The surface $S$ has always Kodaira dimension bigger or equal to zero and the cases of Kodaira dimension zero and one are completely characterized. Several examples of this situation are given.