New posts in Hilbert Spaces

No non-negative continuous function on $[a,b]$ such that $\int_a^b f(t)dt=1, \int_a^b tf(t)dt=c, \int_a^b t^2f(t)dt=c^2$ for $c\in\mathbb{R}$.

Uncountable sum of vectors in a Hilbert Space

Formula for the least element on the spectrum

What is the difference between vector space and dual space?

Quasinilpotent operators satisfying a polynomial identity

Examples of when the Riesz representation theorem doesn't hold

Why is there no matrix representation of a linear operator

A cylinder in infinite-dimensional Hilbert space cannot be homeomorphic to a sphere

Does $\mathcal{B}(\mathcal{H})=\mathcal{H}\otimes\mathcal{H}^*$ in infinite dimensions?

Example of an infinite dimensional Hilbert space that is not an RKHS