Attempt at a classical cancellation of the cosmological constant

I examine some classical models for a relaxing cosmological constant. The relaxation occurs by means of a classical field which ‘‘rolls’’ down a potential hill. I suggest a feedback mechanism in which the action of this field depends upon the scalar curvature of space-time. It is shown that ${\Lambda }_{\mathrm{eff}}$ can fall off faster than the red-shifting radiation density. There are problematic side effects associated with baryonic matter. I discuss these and possible treatments.