Jens de Vries

works on

functional calculus 1 hilbert spaces 1 matrix-valued analytic functions 1 operator theory 1 ρ-contractions 1

From the 1 of 3 linked papers with an AI index.

activity

20242026

collaborators

3 papers

math.FA2026

Complete functional calculus bounds for $I ¨ $ -contractions

Michael Hartz, Jens de Vries

The paper derives sharp, optimal bounds for the functional calculus of ρ‑contractions on Hilbert spaces when applied to matrix‑valued analytic functions on the unit disc, completin…

math.FA2025

The algebraic numerical range as a spectral set in Banach algebras

Hanna Blazhko, Daniil Homza, Felix L. Schwenninger +2

We investigate when the algebraic numerical range is a $C$ -spectral set in a Banach algebra. While providing several counterexamples based on classical ideas as well as combinatori…

math.FA2024

A sharp bound for the functional calculus of $I ¨ $ -contractions

Felix L. Schwenninger, Jens de Vries

Let $A$ be a $I ¨ $ -contraction and $f$ a rational function mapping the closed unit disk into itself. With a new characterization of $I ¨ $ -contractions we prove that \begin{align*} \b…

Complete functional calculus bounds for I¨-contractions

The algebraic numerical range as a spectral set in Banach algebras

A sharp bound for the functional calculus of I¨-contractions

Complete functional calculus bounds for $I ¨ $ -contractions

A sharp bound for the functional calculus of $I ¨ $ -contractions