English

Bohr radius for Banach spaces on simply connected domains

Complex Variables 2026-04-15 v2 Functional Analysis

Abstract

Let H(Ω,X)H^{\infty}(\Omega,X) be the space of bounded analytic functions f(z)=n=0xnznf(z)=\sum_{n=0}^{\infty} x_{n}z^{n} from a proper simply connected domain Ω\Omega containing the unit disk D:={zC:z<1}\mathbb{D}:=\{z\in \mathbb{C}:|z|<1\} into a complex Banach space XX with \normfH(Ω,X)1\norm{f}_{H^{\infty}(\Omega,X)} \leq 1. Let ϕ={ϕn(r)}n=0\phi=\{\phi_{n}(r)\}_{n=0}^{\infty} with ϕ0(r)1\phi_{0}(r)\leq 1 such that n=0ϕn(r)\sum_{n=0}^{\infty} \phi_{n}(r) converges locally uniformly with respect to r[0,1)r \in [0,1). For 1p,q<1\leq p,q<\infty, we denote \begin{equation*} R_{p,q,\phi}(f,\Omega,X)= \sup \left\{r \geq 0: \norm{x_{0}}^p \phi_{0}(r) + \left(\sum_{n=1}^{\infty} \norm{x_{n}}\phi_{n}(r)\right)^q \leq \phi_{0}(r)\right\} \end{equation*} and define the Bohr radius associated with ϕ\phi by Rp,q,ϕ(Ω,X)=inf{Rp,q,ϕ(f,Ω,X):\normfH(Ω,X)1}.R_{p,q,\phi}(\Omega,X)=\inf \left\{R_{p,q,\phi}(f,\Omega,X): \norm{f}_{H^{\infty}(\Omega,X)} \leq 1\right\}. In this article, we extensively study the Bohr radius Rp,q,ϕ(Ω,X)R_{p,q,\phi}(\Omega,X), when XX is an arbitrary Banach space and XX is certain Hilbert space. Furthermore, we establish the Bohr inequality for the operator-valued Ces\'{a}ro operator and Bernardi operator.

Keywords

Cite

@article{arxiv.2111.10880,
  title  = {Bohr radius for Banach spaces on simply connected domains},
  author = {Vasudevarao Allu and Himadri Halder},
  journal= {arXiv preprint arXiv:2111.10880},
  year   = {2026}
}

Comments

We revise the proof of Theorem 1.2. This paper contains 23 pages, 12 figures, 6 tables