New posts in Hilbert Spaces

Proving an inequality with Cauchy-Schwarz

How to characterize self-adjoint operators in terms of orthogonal diagonalizability

Two different definitions of ellipticity

Canonical examples of inner product spaces that are not Hilbert spaces?

Connections between metrics, norms and scalar products (for understanding e.g. Banach and Hilbert spaces)

Elegant proof that $L^2([a,b])$ is separable

Given two basis sets for a finite Hilbert space, does an unbiased vector exist?

On the isometry between bounded linear operators and the dual of nuclear linear operators

Does there exist a real Hilbert space with countably infinite dimension as a vector space over $\mathbb{R}$?

Existence of a non-null and non-negative vector in $F\cup F^\perp$