Integral identities for 3d dualities with SP(2N) gauge groups

In this note we study the reduction of 4d Seiberg duality to 3d for SP(2N) SQCD with an adjoint field. We follow a general prescription that consists in compactifying the dual 4d theories on the circle. This generates an effective 3d duality. The pure 3d duality is obtained by combining the zero radius limit with a real mass flow. Here we perform this limit by a double scaling procedure: we turn on real masses proportional to the radius before shrinking the circle. We apply this mechanism to the reduction of the 4d superconformal index to the three sphere partition function. While the reduction of the 4d index on the circle is straightforward, the 3d limit necessitates the double scaling. We describe this limit on the index, finding the integral identity for the partition functions of the 3d dual theories.