Abstract:
Let A be an operator in a Hilbert space H with Dom(A) is the domain and Ran(A) is the range of
the operator A. An operator A is said to be densely defined if Dom(A) is dense in H. A densely
defined operator A is said to be self-adjoint if A = A (where A is the adjoint of the operator A).
The set of all bounded and everywhere defined operators in H is denoted by B(H) and B(H) is a
Banach space with respect to operator norm k.k.
