Approximating bounded operators in Hilbert space
87897
Bounded operators on separable Hilbert spaces
88535
Relation between the distance from a point to the resolvent set of a self-adjoint operator and the norm of a related operator
62971
About smooth approximation in a Sobolev space
88971
An approximate eigenvalue for $ T \in B(X) $.
61924
Hilbert space in quantum mechanics
137209
Finding the Matrix of a Linear Operator Satisfying a Polynomial
138720
Minimum principle in Hilbert space
64840
A Banach space that is not a Hilbert space
70657
aproximation in Sobolev Spaces
92497
Isometric Embedding of a separable Banach Space into $\ell^{\infty}$
55388
Finding nilpotent and diagonalizable operators for a linear transformation $T$
86481
Let $H$ be an infinite-dimensional separable Hilbert space, show that a Hilbert-Schmidt operator is compact
55533
Tensor Product: Hilbert Spaces
50946
Separable Hilbert space have a countable orthonormal basis
97994
Orthogonality Relations Exercise, Brezis' Book Functional Analysis
66299
Operator whose spectrum is given compact set
60556
Uniform convergence, Bounded derivative.