Definition 2.3.1 (Normal Operator).label Let $H$ be a Hilbert space and $T$ be a closed, densely defined operator, then $T$ is normal if $T^{*}T = TT^{*}$.
Definition 2.3.1 (Normal Operator).label Let $H$ be a Hilbert space and $T$ be a closed, densely defined operator, then $T$ is normal if $T^{*}T = TT^{*}$.