Optimal Control of the Diffusion Coefficient of a Simple Diffusion Process

We consider the optimal control of a one-dimensional diffusion process over a finite time interval. The process may be controlled by varying the diffusion coefficient. The objective is to maximize the expected value of some function of the state, R , at final time. In this paper we investigate the properties of a particular bang-bang control (sigma) 0 , and find necessary and sufficient conditions on R for (sigma) 0 to be optimal.