Spectral Theory for Schrodinger Operators with Interface Transmission Conditions
Interfaces influence transport across biological membranes, habitat boundaries, and composite media. Motivated by these applications, we study two classes of Schrodinger eigenvalue problems with transmission conditions allowing jumps in the solution or its normal derivative. We develop a weighted variational framework that accommodates asymmetric interface coupling and yields self-adjoint realizations in suitable weighted Hilbert spaces. For both problems and their adjoints, we establish discrete spectra, variational eigenvalue characterizations, and eigenfunction completeness in arbitrary spatial dimensions. We prove spectral continuity and identify limiting spectra in singular parameter regimes. We also extend Courant's nodal domain theorem to eigenfunctions that may be discontinuous across the interface. The spectral results further extend to divergence-form elliptic operators under suitable assumptions on the coefficients. These results provide a foundation for analyzing elliptic and parabolic equations with interface transmission conditions.