“…The integer p = deg(M 1 ) corresponds to the level of the five dimensional Chern-Simons term [57]. Therefore by analogy with [42,18,52,30,31,19,29,39,43,32], the refined topological string partition function of Z should be related with the equivariant instanton partition function Z (p) inst (Q, ǫ 1 , ǫ 2 , a 1 , a 2 , y), which has been constructed in [52]. As explained in detail in the next subsection, Z (p) inst (Q, ǫ 1 , ǫ 2 , a 1 , a 2 , y) is the generating function for the χ y -genus of a certain holomorphic bundle on a partial compactification of the instanton moduli space.…”