Wickstead's conjecture on positive projections and non-representable Banach lattice algebras

Fuente: arXiv
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Auteur principal: Muñoz-Lahoz, David
Format: Preprint
Publié: 2026
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author Muñoz-Lahoz, David
author_facet Muñoz-Lahoz, David
contents Let $X$ be a Dedekind complete Banach lattice, and let $P\colon X\to X$ be a positive projection for which the largest central operator below $P$ is $α\operatorname{id}_X$, for some $α\ge 0$. Wickstead conjectured that $α$ must either be $0$ or $1/n$, for some $n \in \mathbb{N}$, and proved it for finite-dimensional $X$. In this paper, we show that the conjecture holds in general. As a consequence, we settle the representation problem for Banach lattice algebras: we show that there exist Banach lattice algebras of dimension $2$ that do not admit a faithful representation as regular operators on any Dedekind complete Banach lattice.
format Preprint
id arxiv_https___arxiv_org_abs_2604_14697
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Wickstead's conjecture on positive projections and non-representable Banach lattice algebras
Muñoz-Lahoz, David
Functional Analysis
Operator Algebras
47B65, 46B42, 46A40, 06F25
Let $X$ be a Dedekind complete Banach lattice, and let $P\colon X\to X$ be a positive projection for which the largest central operator below $P$ is $α\operatorname{id}_X$, for some $α\ge 0$. Wickstead conjectured that $α$ must either be $0$ or $1/n$, for some $n \in \mathbb{N}$, and proved it for finite-dimensional $X$. In this paper, we show that the conjecture holds in general. As a consequence, we settle the representation problem for Banach lattice algebras: we show that there exist Banach lattice algebras of dimension $2$ that do not admit a faithful representation as regular operators on any Dedekind complete Banach lattice.
title Wickstead's conjecture on positive projections and non-representable Banach lattice algebras
topic Functional Analysis
Operator Algebras
47B65, 46B42, 46A40, 06F25
url https://arxiv.org/abs/2604.14697