Two-dimensional electron liquid with disorder in a weak magnetic field

We present the effective theory for the low-energy dynamics of two-dimensional interacting electrons in the presence of a weak short-range disorder and a weak perpendicular magnetic field, with the filling factor γ ? 1. We investigate the exchange enhancement of the g factor, the effective mass, and the decay rate of the simplest spin wave excitations at γ=2N+1. We obtain the enhancement of the field-induced gap in the tunneling density of states and the dependence of the tunneling conductivity on the applied bias.