Comments on worldsheet description of the Omega background Original Research Article

Nekrasovʼs partition function is defined on a flat bundle of image over image called the Omega background. When the fibration is self-dual, the partition function is known to be equal to the topological string partition function, which computes scattering amplitudes of self-dual gravitons and graviphotons in type II superstring compactified on a Calabi–Yau manifold. We propose a generalization of this correspondence when the fibration is not necessarily self-dual.