On the response of composite fermions to weak electrostatic potentials

We establish that the response to static perturbations of two-dimensional electron systems (2DESs), exposed to magnetic field B, in states with the Landau-level filling fractions \nu close to one such as 1/2, is singularly different from that of 2DESs at small |B|. Thus in addition to demonstrating the sever inadequacy of the treatment of composite fermions as non-interacting particles, we show, in contradiction to a recent theoretical finding, that the physical origin of the observed behaviour of the dc longitudinal magneto-resistivity for \nu close to 1/2 in periodically modulated 2DESs remains to be determined.