Weak-coupling approach to interaction-induced deformation of the Fermi surface in the two-dimensional Hubbard model

We investigate the interaction-induced deformation of the Fermi surface in the two-dimensional Hubbard model on the triangular lattice in the weak-cou pling regime within the second-order perturbation theory. In systems withou t frustration, at the filling equal to or close to half-filling, the direct ion of the deformation of the Fermi surface is the direction toward the Fer mi surface at half-filling with the smaller transfer amplitude set to zero, whose nesting vector is commensurate with the underlying lattice. On the o ther hand, in systems with frustration, the Fermi surface is not deformed b y the interaction because of the frustration.