"essential self-adjointness" . . . "the spectral theory of Hermitian operators" . "Self-adjoint operator" . . "self-adjoint" . . "hermitian operators" . "resolution of the identity" . "spectral theorem for self-adjoint operators" . "pure point spectrum" . "spectral multiplicity theory" . "unitarily equivalent" . "unitarily non-equivalent" . "self-adjoint operators" . "self-adjoint operator" . "Self-adjoint operator" . "self-adjoint linear operator" . "implies" . . "Self-adjoint operator#Spectral multiplicity theory" . "Hermitian" . "unitary equivalence" . "self-adjointness" . "Self-adjoint_operator#Symmetric operators" . "Self-adjoint_operator" . "Self-adjoint unbounded operators" . "Self-adjoint operator#Self-adjoint extensions in quantum mechanics" . "spectral theorem" . "symmetric operators" . "Self-adjoint operator#Extensions of symmetric operators" . . "symmetric operator" . "Spectral theorem" . "Hermitian operator" . "Hermitian operators" .