Resurgence in 2-dimensional Yang–Mills and a genus-altering deformation

Abstract

Abstract We study resurgence in the context of the partition function of 2-dimensional SU(N) and U(N) Yang–Mills theory on a surface of genus h. After discussing the properties of the transseries in the undeformed theory, we add a term to the action to deform the theory. The partition function can still be calculated exactly, and the deformation has the effect of analytically continuing the effective genus parameter in the exact answer so that it is noninteger. In the deformed theory we find new saddle solutions and study their properties. In this context each saddle contributes an asymptotic series to the transseries which can be analyzed using Borel-Écalle resummation. For specific values of the deformation parameter we find Cheshire cat points where the asymptotic series in the transseries truncate to a few terms. We also find new partial differential equations satisfied by the partition function, and a number of applications of these are explained, including low-order/low-order resurgence.