Vertex algebras and 4-manifold invariants

We propose a way of computing 4-manifold invariants, old and new, as chiral correlation functions in half-twisted 2d $mathcal{N}=(0,2)$ theories that arise from compactification of fivebranes. Such formulation gives a new interpretation of some known statements about Seiberg-Witten invariants, such as the basic class condition, and gives a prediction for structural properties of the multi-monopole invariants and their non-abelian generalizations.