Michael Hartz

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math.FA2026

Complete functional calculus bounds for $ρ$ -contractions

Michael Hartz, Jens de Vries

Let $T$ be a $ρ$ -contraction on a Hilbert space. We establish sharp bounds for the functional calculus of $T$ for matrix-valued analytic functions on the unit disc. These are compl…

math.FA2026

From Clouatre-Ostermann-Ransford to Okubo-Ando

Michael Hartz, John E. McCarthy

We prove that if $θ$ is a continuous unital homomorphism of an operator algebra $A$ into $B (H)$ , and $β$ is in the dual space of $A$ , then the completely bounded norm of…

math.FA2026

On the Schur-Agler Norm

Michael Hartz, Yi Wang

We establish a new description of the Schur-Agler norm of a holomorphic function on the polydisc as the solution of a convex optimization problem. Consequences of this description…

math.FA2024

Potential theory and boundary behavior in the Drury-Arveson space

Nikolaos Chalmoukis, Michael Hartz

We develop a notion of capacity for the Drury-Arveson space $H_{d}^{2}$ of holomorphic functions on the Euclidean unit ball. We show that every function in $H_{d}^{2}$ has a non-tangential…

Complete functional calculus bounds for ρ-contractions

From Clouatre-Ostermann-Ransford to Okubo-Ando

On the Schur-Agler Norm

Potential theory and boundary behavior in the Drury-Arveson space

Complete functional calculus bounds for $ρ$ -contractions