  Persistent and radiation-induced currents in distorted narrow quantum rings
are theoretically investigated. We show that ring distorsions can be described
using a geometrical potential term. We analyse the effect of this term on the
current induced by a magnetic flux (persistent current) and by a polarized
coherent electromagnetic field (radiation-induced current). The strongest
effects in persistent currents are observed for distorted rings with a small
number of electrons. The distortion smoothes the current oscillations as a
function of the magnetic flux and changes the temperature dependence of the
current amplitude. For radiation-induced currents, the distortion induces an ac
component in the current and affects its dependence on the radiation frequency
and intensity.
