Interface line operators in N=4 SYM theories and supersymmetric indices

A bstract We study configurations of two N=4 N = 4 super Yang-Mills theories of unitary gauge groups connected by the BPS interfaces involving line operators. We find strong evidence of S-duality of the configurations as precise matching of the line defect half-indices which enumerate the BPS local operators at the junctions of the interfaces and line operators. The interface line defect half-indices are expressible as intriguing closed-form formulae involving the q -binomial coefficients and the principal specializations of the Schur functions.