Abstract
Let $X$ be a Banach function space over the unit circle such that the Riesz projection $P$ is bounded on $X$ and let $H[X]$ be the abstract Hardy space built upon $X$. We show that the essential norm of the Toeplitz operator $T(a):H[X]\to H[X]$ coincides with $\|a\|_{L^\infty}$ for every $a\in C+H^\infty$ if and only if the essential norm of the backward shift operator $T(\mathbf{e}_{-1}):H[X]\to H[X]$ is equal to one, where $\mathbf{e}_{-1}(z)=z^{-1}$. This result extends an observation by B\"ottcher, Krupnik, and Silbermann for the case of classical Hardy spaces.
Original language | English |
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Article number | 8 (2025) |
Number of pages | 9 |
Journal | Boletín de la Sociedad Matemática Mexicana |
Volume | 31 |
Publication status | Published - 8 Nov 2024 |
Keywords
- Banach function space
- abstract Hardy space
- Toeplitz operator
- essential norm