Abstract
The well known Coburn lemma can be stated as follows: a nonzero Toeplitz operator $T(a)$ with symbol $a\in L^\infty(\mathbb{T})$ has a trivial kernel or a dense range on the Hardy space $H^p(\mathbb{T})$ with $p\in(1,\infty)$. We show that an analogue of this result does not hold for the Hardy-Marcinkiewicz (weak Hardy) spaces $H^{p,\infty}(\mathbb{T})$ with $p\in(1,\infty)$: there exist continuous nonzero functions $a:\mathbb{T}\to\mathbb{C}$ depending on $p$ such that $\operatorname{dim} \left(\operatorname{Ker} T(a)\right) = \infty$ and $\operatorname{dim} \left(H^{p,\infty}(\mathbb{T})/\operatorname{clos}_{H^{p,\infty}(\mathbb{T})}\big(\operatorname{Ran} T(a)\big)\right) = \infty$.
Original language | English |
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Title of host publication | Toeplitz Operators and Random Matrices |
Subtitle of host publication | In Memory of Harold Widom |
Editors | Estelle Basor, Albrecht Böttcher, Torsten Ehrhardt, Craig Tracy |
Publisher | Birkhaeuser Publishing Ltd |
Pages | 463-476 |
Number of pages | 14 |
Publication status | Published - 2 Jan 2023 |