In this book, Professor Pinsky gives a self-contained account of the construction and basic properties of diffusion processes, including both analytic and probabilistic techniques. He starts with a rigorous treatment of the spectral theory of elliptic operators with nice coefficients on smooth, bounded domains, and then develops the theory of the generalized principal eigenvalue and the related criticality theory for elliptic operators on arbitrary domains. He considers Martin boundary theory and calculates the Martin boundary for several classes of operators. The book provides an array of criteria for determining whether a diffusion process is transient or recurrent. Also introduced are the theory of bounded harmonic functions, and Brownian motion on a manifold. Many results that form the folklore of the subject are given a rigorous exposition, making this book a useful reference for the specialist, and an excellent guide for the graduate student.
1. Existence and uniqueness for diffusion processes; 2. The basic properties of diffusion processes; 3. The spectral theory of elliptic operators on smooth bounded domains; 4. Generalized spectral theory for operators on arbitrary domains; 5. Applications to the one-dimensional case and the radially symmetric multi-dimensional case; 6. Criteria for transience or recurrence and explosion or non-explosion of diffusion processes; 7. Positive harmonic functions and the Martin boundary: general theory; 8. Positive harmonic functions and the Martin boundary: applications to certain classes of operators; 9. Bounded harmonic functions and applications to Brownian motion and the Laplacian on a manifold of non-positive curvature.