Electronic states in correlated three-coupled chains
  Three-coupled chains of quarter-filled Hubbard model with dimerization have been studied for periodic boundary conditions. By use of a renormalization group method, it is found that the interchain hopping is renormalized to zero leading to confinement when charge gap becomes larger than the effective interchain hopping energy. Such a result of confinement is compared with that of two-coupled chains. 
M. Tsuchiizu, Y. Suzumura