Abstract
Single-wall carbon nanotubes with on-site interaction U≪t are studied by a controlled renormalization group method. When formulated as a system of N f flavors of interacting Dirac fermions, the effective model at generic filling resembles a set of quasi-1D Hubbard chains. For the undoped (N y ,N y ) armchair and the (N x ,- N x ) zigzag with N x = 3n, specific mappings to the two-chain Hubbard model at half filling with effective interaction u eff = U/N y and 2U/N x are found from this more general equivalence. The phase diagrams of the (3,3) armchair and the (6,-6) zigzag at generic fillings are studied and compared as an example.