Violation of Luttinger's theorem in strongly correlated electronic systemswithin a 1/N expansion

We study the 1/N expansion of a generic, strongly correlated electron model (SU(N) symmetric Hubbard model with U = infinity and N degrees of freedom per lattice site) in terms of X operators. The leading order of the expansi on describes a usual Fermi liquid with renormalized, stable particles. The next-to-leading order violates Luttinger's theorem ifa finite convergence r adius for the 1/N expansion for a fixed and non-vanishing doping away from half-filling is assumed. We find that the volume enclosed by the Fermi surf ace, is at large, but finite N's and small dopings larger than at N = infin ity. As a byproduct an explicit expression for the electronic self-energy i n O(1/N) is given which cannot be obtained by factorization or mode-couplin g assumptions but contains rather sophisticated vertex corrections.