I want to learn the spectral theory of linear elliptic operators in bounded and unbounded domains in $R^n$, in particular for Laplacian and Schrodinger operators. Please suggest me some reference. I have studied second order Elliptic pde from Evans Chapter 6. There he discusses spectrum for case of bounded domain. I want to study how spectrum behaves in case of unbounded domain also. I want to explore functional analytic viewpoint of Elliptic Operators.
Post Closed as "Needs details or clarity" by Alexey Ustinov, Piotr Hajlasz, Daniele Tampieri, Dima Pasechnik, Alec Rhea