Non-planar corrections in orbifold/orientifold 𝒩 = 2 superconformal theories from localization

We study non-planar corrections in two special 𝒩 = 2 superconformal SU( N ) gauge theories that are planar-equivalent to 𝒩 = 4 SYM theory: two-nodes quiver model with equal couplings and 𝒩 = 2 vector multiplet coupled to two hypermultiplets in rank-2 symmetric and antisymmetric representations. We focus on two observables in these theories that admit representation in terms of localization matrix model: free energy on 4-sphere and the expectation value of half-BPS circular Wilson loop. We extend the methods developed in arXiv:2207.11475 to derive a systematical expansion of non-planar corrections to these observables at strong ’t Hooft coupling constant λ . We show that the leading non- planar corrections are given by a power series in λ 3 / 2 /N 2 with rational coefficients. Sending N and the coupling constant λ to infinity with λ 3 / 2 /N 2 kept fixed corresponds to the familiar double scaling limit in matrix models. We find that in this limit the observables in the two models are related in a remarkably simple way: the free energies differ by the factor of 2, whereas the Wilson loop expectation values coincide. Surprisingly, these relations hold only at strong coupling, they are not valid in the weak coupling regime. We also discuss a dual string theory interpretation of the leading corrections to the free energy in the double scaling limit suggesting their relation to curvature corrections in type IIB string effective action.