Definition 2.1.6 (Essentially Self-Adjoint).label Let $H$ be a Hilbert space and $T: D(T) \to H$ be a semipositive operator, then $T$ is essentially self-adjoint if the Friedrichs extension is its unique self-adjoint extension.
Definition 2.1.6 (Essentially Self-Adjoint).label Let $H$ be a Hilbert space and $T: D(T) \to H$ be a semipositive operator, then $T$ is essentially self-adjoint if the Friedrichs extension is its unique self-adjoint extension.