A Family of N=2 Gauge Theories with Exact S-Duality

Abstract

We study an infinite family of N=2 $Sp(2n)$ gauge theories that naturally arise from the D3-brane probe dynamics in F-theory. The matter sector consists of four fundamental and one antisymmetric tensor hyper multiplets. We propose that, in the limit of vanishing bare masses, the theory has exact $SO(8)\sdtimes SL(2,Z)$ duality. We examine the semiclassical BPS spectrum in the Coulomb phase by quantizing various monopole moduli space dynamics, and show that it is indeed consistent with the exact S-duality.