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Morrey spaces over the unit circle cannot be renormed to become rearrangement-invariant

Functional Analysis 2025-04-07 v1

Abstract

Let 1p<1\le p<\infty and 0<λ<10<\lambda<1. We consider the classical Morrey space Lp,λ(T)L^{p,\lambda}(\mathbb{T}) over the unit circle T\mathbb{T}. We show that there are equimeasurable functions f,g:TRf,g:\mathbb{T}\to\mathbb{R} such that gLp,λ(T)g\in L^{p,\lambda}(\mathbb{T}) but fLp,λ(T)f\notin L^{p,\lambda}(\mathbb{T}). This implies that the the space Lp,λ(T)L^{p,\lambda}(\mathbb{T}) cannot be renormed to become rearrangement-invariant.

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Cite

@article{arxiv.2504.03366,
  title  = {Morrey spaces over the unit circle cannot be renormed to become rearrangement-invariant},
  author = {Oleksiy Karlovych and Eugene Shargorodsky},
  journal= {arXiv preprint arXiv:2504.03366},
  year   = {2025}
}

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4 pages