Classification and stability of phases of the multicomponent one-dimensional electron gas

The classification of the ground-state phases of complex one-dimensional electronic systems is considered in the context of a fixed-point strategy. Examples are multichain Hubbard models, the Kondo-Heisenberg model, and the one-dimensional electron gas in an active environment.;It is shown that, in order to characterize the low-energy physics, it is necessary to analyze the perturbative stability of the possible fixed paints, to identify all discrete broken symmetries; and to specify the quantum numbers and elementary wave vectors of the gapless excitations. Many previously proposed exotic phases of multichain Hubbard models are shown to be unstable because of the "spin-gap proximity effect." A useful tool in this analysis is a generalization of Luttinger's theorem, which shows that there is a gapless even-charge mode, in any incommensurate N-component system. [S0163-1829(99)03124-0].