Seiberg–Witten and Casson–Walker Invariants for Rational Homology 3-Spheres

We consider a modified version of the Seiberg–Witten invariants for rational homology 3-spheres, obtained by adding to the original invariants a correction term which is a combination of η-invariants. We show that these modified invariants are topological invariants. We prove that an averaged version of these modified invariants equals the Casson–Walker invariant. In particular, this result proves an averaged version of a conjecture of Ozsváth and Szabó on the equivalence between their θ invariant and the Seiberg–Witten invariant of rational homology 3-spheres