Abstract
The effect of a driving field on the dynamics of a two-level system coupled to a bath is studied. Allowance is made for arbitrary coupling between the two levels, arbitrary coupling of the two levels to the bath, and an arbitrary bath. For a given two-level system, the coupling between the two levels can be made to vanish by applying a high-frequency driving field whose period is much shorter than any characteristic time scale of the driven system, under the condition that the coupling of the driven system to the field is independent of the bath coordinates.