On Calabi-Yau Manifolds at Strong Topological String Coupling

It was recently shown that integrating out M2 states on Calabi-Yau manifolds captures non-perturbative topological string physics in the free energy. In this note, It has been shown that the resulting expression manifests a certain duality symmetry: the free energy at strong string coupling is equal to the Calabi-Yau period at weak string coupling. The duality yields the appropriate prescription for completing the integrating out in the ultraviolet.