A connected sum formula for involutive Heegaard Floer homology

Abstract

We prove a connected sum formula for involutive Heegaard Floer homology, and use it to study the involutive correction terms of connected sums. In particular, we give an example of a three-manifold with $\underline{d}(Y)\ne d(Y)\ne \overline{d}(Y)$. We also construct a homomorphism from the three-dimensional homology cobordism group to an algebraically defined Abelian group, consisting of certain complexes (equipped with a homotopy involution) modulo a notion of local equivalence.

54 pages; fixed the calculation in Prop.1.5; a few other changes in the exposition