Does Hilbert space has orthogonal/orthonormal basis?
14550
Every Hilbert space has an orthonomal basis - using Zorn's Lemma
63032
Why is it true that every finite-dimensional inner product space is a Hilbert space?
52946
If $X$ is an orthogonal matrix, why does $X^TX = I$?
120766
Prove ${y_n}$ is a basis for a Hilbert space $H$.
91636
Are all eigenvectors, of any matrix, always orthogonal?
14166
Hilbert space of harmonic oscillator: Countable vs uncountable?
92281
Normal Operator that is not Self-Adjoint
144151
An orthonormal set cannot be a basis in an infinite dimension vector space?
97949
Existence of a $\mathbb C$-Banach space isometric to a Hilbert Space but whose norm is not induced by an inner product?
87940
Question about bilinear form on Hilbert space
65888
A counterexample to theorem about orthogonal projection
83360
The completion of a separable inner product space is a separable Hilbert space
70475
Proving a basis for inner product space V when $||e_j-v_j||< \frac{1}{\sqrt{n}}$.
91257
Fourier basis functions
135650
Sequences in Hilbert spaces
30017
Orthogonality and linear independence
114524
Proof Verification: the orthogonal complement of the column space is the left nullspace