  In \prl 84, 258 (2000), Mateos conjectured that current reversal in a
classical deterministic ratchet is associated with bifurcations from chaotic to
periodic regimes. This is based on the comparison of the current and the
bifurcation diagram as a function of a given parameter for a periodic
asymmetric potential. Barbi and Salerno, in \pre 62, 1988 (2000), have further
investigated this claim and argue that, contrary to Mateos' claim, current
reversals can occur also in the absence of bifurcations. Barbi and Salerno's
studies are based on the dynamics of one particle rather than the statistical
mechanics of an ensemble of particles moving in the chaotic system. The
behavior of ensembles can be quite different, depending upon their
characteristics, which leaves their results open to question. In this paper we
present results from studies showing how the current depends on the details of
the ensemble used to generate it, as well as conditions for convergent behavior
(that is, independent of the details of the ensemble). We are then able to
present the converged current as a function of parameters, in the same system
as Mateos as well as Barbi and Salerno. We show evidence for current reversal
without bifurcation, as well as bifurcation without current reversal. We
conjecture that it is appropriate to correlate abrupt changes in the current
with bifurcation, rather than current reversals, and show numerical evidence
for our claims.
