On symplectic caps

Abstract

An important class of contact 3--manifolds are those that arise as links of rational surface singularities with reduced fundamental cycle. We explicitly describe symplectic caps (concave fillings) of such contact 3--manifolds. As an application, we present a new obstruction for such singularities to admit rational homology disk smoothings.

17 pages, 6 figures. Section 2 rewritten, proof of Theorem 2.1 corrected