LANDAU THEORY FOR A METAL-INSULATOR-TRANSITION

The nonlinear sigma model for disordered interacting electrons is studied in spatial dimensions d > 4. The critical behavior at the metal-insulator transition is determined exactly, and found to be that of a standard Landau-Ginzburg-Wilson phi4 theory with the single-particle density of states as the order parameter. All static exponents have their mean-field values, and the dynamical exponent z = 3. partial derivative n/partial derivative mu is critical with an exponent of 1/2, and the electrical conductivity vanishes with an exponent s = 1. The transition is qualitatively different from the one found in the same model in a 2 + epsilon expansion.