Convexity of Berezin Range and Berezin Radius Inequalities via a class of Seminorm

Abstract

Let $B(\mathcal{H})$ denote the $C^*$-algebra of all bounded linear operators acting on a reproducing kernel Hilbert space $\mathcal{H}(\Omega).$ In this paper, we introduce a new family of seminorms on $B(\mathcal{H})$, called the $\sigma_t$-Berezin norm, defined as $$ \|A\|_{{ber}_{\sigma_t}} = \sup_{\lambda,\mu\in \Omega} \left\{ \left( \left|\left\langle A\hat{k}_\lambda,\hat{k}_\mu\right\rangle\right|^p \, \sigma_t \, \left|\left\langle A^*\hat{k}_\lambda,\hat{k}_\mu\right\rangle\right|^p \right)^{\frac{1}{p}} \right\}, $$ where $A\in B(\mathcal{H}), ~p \geq 1, ~t \in [0,1]$ and ~$\sigma_t$ denotes an interpolation path of a symmetric mean $\sigma$. We show that this family of seminorms characterizes invertible operators that are unitary. Several fundamental properties of the $\sigma_t$-Berezin norm are established, along with a collection of new inequalities that yield refined upper bounds for the Berezin radius of bounded linear operators, thereby improving existing results in the literature. Furthermore, we investigate the convexity of the Berezin range of operators acting on weighted Hardy space and Fock space over $\mathbb{C}^n$. We characterised the convexity of the Berezin range of composition operator with elliptic automorphism and finite rank operators with different weights on the weighted Hardy space. We also characterized convexity of the Berezin range of composition operator on Fock space over $\mathbb{C}^n$ with symbol $\phi(z)=Az$, where $A$ is a scalar matrix of order $n$.