English

A von Neumann type inequality for an annulus

Functional Analysis 2021-09-23 v2

Abstract

Let Ar={r<z<1}A_r=\{r<|z|<1\} be an annulus. We consider the class of operators Fr:={TB(H):r2T1(T1)+TTr2+1,σ(T)Ar}\mathcal{F}_r:=\{T\in\mathcal{B}(H): r^2T^{-1}(T^{-1})^*+TT^*\le r^2+1,\hspace{0.08 cm}\sigma(T)\subset A_r\} and show that for every bounded holomorphic function ϕ\phi on Ar:A_r: supTFrϕ(T)2ϕ,\sup_{T\in\mathcal{F}_r}||\phi(T)||\le\sqrt{2}||\phi||_{\infty}, where the constant 2\sqrt{2} is the best possible. We do this by characterizing the calcular norm induced on H(Ar)H^{\infty}(A_r) by Fr\mathcal{F}_r as the multiplier norm of a suitable holomorphic function space on ArA_r.

Keywords

Cite

@article{arxiv.2106.06013,
  title  = {A von Neumann type inequality for an annulus},
  author = {Georgios Tsikalas},
  journal= {arXiv preprint arXiv:2106.06013},
  year   = {2021}
}

Comments

12 pages, updated list of references in v2

R2 v1 2026-06-24T03:04:33.696Z