5D partition functions, q-Virasoro systems and integrable spin-chains

Abstract: We analyze (Formula presented.) theories on S5 and S4 × S1, showing how their partition functions can be written in terms of a set of fundamental 5d holomorphic blocks. We demonstrate that, when the 5d mass parameters are analytically continued to suitable values, the S5 and S4 × S1 partition functions degenerate to those for S3 and S2 × S1. We explain this mechanism via the recently proposed correspondence between 5d partition functions and correlators with underlying q-Virasoro symmetry. From the q-Virasoro 3-point functions, we axiomatically derive a set of associated reflection coefficients, and show that they can be geometrically interpreted in terms of Harish-Chandra c-functions for quantum symmetric spaces. We link these particular c-functions to the types appearing in the Jost functions encoding the asymptotics of the scattering in integrable spin-chains, obtained taking different limits of the XYZ model to XXZ-type.