Inhomogeneous transport and derivative relations in the quantum Hall regime

Several derivative relations have been observed in the quantum Hall regime including a relation between elements of the macroscopic resistivity tensor R-xx = alpha B(dR(xy)/dB), a relation between elements of the macroscopic thermopower tensor S-y alpha = alpha B(dS(xx)/dB), as well as a similar rel ation observed in acoustoelectric experiments there B is the magnetic field and alpha is a constant). It has been proposed in a number of recent works by the author and collaborators that these relations can be explained with a model of classical transport in an inhomogeneous medium. We review these works and briefly discuss to what extent the models which predict these de rivative relations are appropriate for describing the experimental systems. (C) 1998 Elsevier Science B.V. All rights reserved.