Linear Magnetic Response of Disordered Metallic Rings: Large   Contribution from Forward Scattering Interactions
  We calculate the effect of electron-electron interactions involving vanishing momentum transfer (forward scattering) on the orbital linear magnetic response of disordered metal rings pierced by a magnetic flux phi. Using the bulk value of the Landau parameter F_0 for copper, we find that in the experiment by L\'{e}vy {\it{et al.}} [Phys. Rev. Lett. {\bf{64}}, 2074 (1990)] the forward scattering contribution to the linear magnetic response is larger than the corresponding contribution from large momentum transfers considered by Ambegaokar and Eckern [Phys. Rev. Lett. {\bf{65}}, 381 (1990)]. However, outside the regime of validity of linear response and to first order in the effective screened interaction the persistent current is dominated by scattering processes involving large momentum transfers. 
Long Phi Chau and Peter Kopietz