A model of optimal consumption and portfolio choice that captures the notions of local substitution and irreversible purchases of durable goods is studied. Necessary and sufficient conditions for a consumption and portfolio policy to be optimal are provided. A closed-form solution of the optimal...

This paper provides sufficient conditions for the equilibrium price system and a vector of exogenously specified state variable processes to form a diffusion process in a pure exchange economy. The conditions involve smoothness of agents' utility functions and certain nice properties of the...