  The paper contains a simple semi-quantitative analysis of a structure of
solution to the exact Bogolyubov functional equation for a particle interacting
with ideal gas and driven by an external force, in comparison with solutions to
model kinetic equations for the same system. It is shown that the exact
equation inevitably predicts existence of significant 1/f-type fluctuations in
mobility of the particle, and this result directly extends to particles in
arbitrary fluid.
