Discrete vs Continuous spectra of operators
38878
Why are eigenfunctions which correspond to discrete/continuous eigenvalue spectra guaranteed to be normalizable/non-normalizable?
57839
Real analysis: density and continuity
1048
Discreteness of set of energy eigenvalues
8805
Bounded linear operators that commute with translation
23089
Differences between symmetric, Hermitian, self-adjoint, and essentially self-adjoint operators
119831
bounded operator $T$ is not compact then there exists an orthonormal sequence $e_n$ and $d>0$ such that $\|T(e_n)\|>d$ for all $n\in\Bbb{N}$?
56211
An operator that commutes with another operator $T$ with distinct characteristic values is a polynomial in $T$
96452
Is the closedness of the image of a Fredholm operator implied by the finiteness of the codimension of its image?
3038
For positive invertible operators $C\leq T$ on a Hilbert space, does it follow that $T^{-1}\leq C^{-1}$?
36826
Products of Differential Operators
142782
Operator< and strict weak ordering
103045
Composition of Proximal Operators
72240
Prove that if a linear operator is continuous, then it is bounded.
137890
Diagonalizable Operators and characteristic polynomials
119775
Density of finite rank operator in compact operators on Hilbert spaces
93062
Is Every Invariant Subspace the Kernel of an polynomial applied in the operator?
98535
Are eigenstates of the position operator continuous?