Closure of the Set of Hilbert-Schmidt Operators
87897
Bounded operators on separable Hilbert spaces
137209
Finding the Matrix of a Linear Operator Satisfying a Polynomial
14203
Finding the creation/annihilation operators
51313
Extension of linearly independent set to a basis in an infinite dimensional vector space
88535
Relation between the distance from a point to the resolvent set of a self-adjoint operator and the norm of a related operator
46698
Showing a set is closed under inverses
128457
Show that $T$ is a compact operator
14550
Every Hilbert space has an orthonomal basis - using Zorn's Lemma
119775
Density of finite rank operator in compact operators on Hilbert spaces
86717
Completeness of $\langle \mathscr{C} [0, 1], \| \cdot \|_1 \rangle$
141762
The direct sum of two closed subspace is closed? (Hilbert space)
128361
The kernel and range of the powers of a self-adjoint operator
69893
An inner product space and its proper closed subspace with trivial orthogonal complement
29230
Orthogonality of Hermite functions
136909
Functional Analysis: The rank of an operator detemines if it's a compact operator.
82355
When is the image of a linear operator (between Banach spaces) closed?
57609
Hahn-Banach proof by extension of basis