Harnessing S-duality in $$ \mathcal{N} $$ = 4 SYM & supergravity as SL(2, ℤ)-averaged strings

Abstract

AbstractWe develop a new approach to extracting the physical consequences of S-duality of four-dimensional$$ \mathcal{N} $$N= 4 super Yang-Mills (SYM) and its string theory dual, based on SL(2, ℤ) spectral theory.We observe that CFT observables 𝒪, invariant under SL(2, ℤ) transformations of a complexified gauge couplingτ, admit a unique spectral decomposition into a basis of square-integrable functions. This formulation has direct implications for the analytic structure of$$ \mathcal{N} $$N= 4 SYM data, both perturbatively and non-perturbatively in all parameters. These are especially constraining for the structure of instantons:k-instanton sectors are uniquely determined by the zero- and one-instanton sectors, and Borel summable series aroundk-instantons have convergence radii with simplek-dependence. In largeNlimits, we derive the existence and scaling of non-perturbative effects, in bothNand the ‘t Hooft coupling, which we exhibit for certain$$ \mathcal{N} $$N= 4 SYM observables. An elegant benchmark for these techniques is the integrated stress tensor multiplet four-point function, conjecturally determined by [1] for allτfor SU(N) gauge group; we elucidate its form, and explain how the SU(2) case is the simplest possible observable consistent with SL(2, ℤ)-invariant perturbation theory.These results have ramifications for holography. We explain how$$ \left\langle \mathcal{O}\right\rangle $$O, the ensemble average of 𝒪 over the$$ \mathcal{N} $$N= 4 supersymmetric conformal manifold with respect to the Zamolodchikov measure, is cleanly isolated by the spectral decomposition. We prove that the largeNlimit of$$ \left\langle \mathcal{O}\right\rangle $$Oequals the largeN, large ‘t Hooft coupling limit of 𝒪. Holographically speaking,$$ \left\langle \mathcal{O}\right\rangle $$O= 𝒪sugra, its value in type IIB supergravity on AdS5× S5. This result, which extends to all orders in 1/N, embeds ensemble averaging into the traditional AdS/CFT paradigm. The statistics of the SL(2, ℤ) ensemble exhibit both perturbative and non-perturbative 1/Neffects. We discuss further implications and generalizations to other AdS compactifications of string/M-theory.