Kinetic Mixing at Strong Coupling
  A common feature of many string-motivated particle physics models is additional strongly coupled U(1)'s. In such sectors, electric and magnetic states have comparable mass, and integrating out modes also charged under U(1) hypercharge generically yields CP preserving electric kinetic mixing and CP violating magnetic kinetic mixing terms. Even though these extra sectors are strongly coupled, we show that in the limit where the extra sector has approximate N = 2 supersymmetry, we can use formal methods from Seiberg-Witten theory to compute these couplings. We also calculate various quantities of phenomenological interest such as the cross section for scattering between visible sector states and heavy extra sector states, as well as the effects of supersymmetry breaking induced from coupling to the MSSM. 
Michele Del Zotto, Jonathan J. Heckman, Piyush Kumar, Arada Malekian,   and Brian Wecht
hep-ph hep-th