Equivalence of Three Wall Crossing Formulae

Abstract

The wall crossing formula of Kontsevich and Soibelman gives an implicit relation between the BPS indices on two sides of the wall of marginal stability by equating two symplectomorphisms constructed from the indices on two sides of the wall. The wall crossing formulae of Manschot, Pioline and the author give two apparently different explicit expressions for the BPS index on one side of the wall in terms of the BPS indices on the other side. We prove the equivalence of all the three formulae.

LaTeX file, 45 pages; v2: added eq.(2.10) containing explicit wall crossing formula for numerical invariants and comments on its possible connection to Joyce-Song formula, added references and some additional minor clarifications; added a simpler proof suggested by the anonymous referee, added other clarifications, version to appear in CNTP, 51 pages