Higher derivative quantum gravity in two dimensions

It is proposed to study geometrodynamics in two space-time dimensions described by a higher derivative action. The Hamilton-Jacobi equation in the superspace approach is exactly solved. Based on the WKB approximation, we argue that the system is stable. It is suggested that within a canonical framework for the exact quantization, there is a built-in mechanism by which the physical cosmological constant always vanishes, irrespective of its bare value.