  In a recent Letter, Bergsten and co-authors have studied the resistance
oscillations with gate voltage and magnetic field in arrays of semiconductor
rings and interpreted the oscillatory magnetic field dependence as
Altshuler-Aronov-Spivak (AAS) oscillations and oscillatory dependence on gate
voltage as the Aharonov-Casher (AC) effect. This Comment shows that Bergsten
and co-authors incorrectly identified AAS effect as a source of resistance
oscillations in magnetic field, that spin relaxation in their experimental
setting is strong enough to destroy oscillatory effects of spin origin, and
that the oscillations are caused by changes in carrier density and the Fermi
energy by gate, and are unrelated to spin.
