{"title":"Gabor frames with atoms in M^q(R) but not in M^p(R) for any 1\\leq p < q \\leq 2","authors":"Pu-Ting Yu","doi":"arxiv-2408.16593","DOIUrl":null,"url":null,"abstract":"This paper consists of two parts. In the first half, we solve the question\nraised by Heil as to whether the atom of a Gabor frame must be in\n$M^p(\\mathbb{R})$ for some $1<p<2$. Specifically, for each $0<\\alpha \\beta \\leq 1$ and $1<q\\leq 2$ we explicitly construct\nGabor frames $\\mathcal{G}(g,\\alpha,\\beta)$ with atoms in $M^q(\\mathbb{R})$ but\nnot in $M^{p}(\\mathbb{R})$ for any $1\\leq p<q$. To construct such Gabor frames,\nwe use box functions as the window functions and show that $$f = \\sum_{k,n\\in\n\\mathbb{Z}} \\langle f,M_{\\beta n}T_{\\alpha k}\n\\mathcal{F}(\\chi_{[0,\\alpha]})\\rangle M_{\\beta n}T_{\\alpha k} (\n\\mathcal{F}(\\chi_{[0,\\alpha]}))$$ holds for $f\\in M^{p,q}(\\mathbb{R})$ with\nunconditional convergence of the series for any $0<\\alpha\\beta \\leq 1$,\n$1<p<\\infty$ and $1\\leq q<\\infty$. In the second half of this paper, we study two questions related to\nunconditional convergence of Gabor expansions in modulation spaces. Under the\nassumption that the window functions are chosen from $M^p(\\mathbb{R})$ for some\n$1\\leq p\\leq 2,$ we will prove several equivalent statements that the equation\n$f = \\sum_{k,n\\in \\mathbb{Z}} \\langle f, M_{\\beta n}T_{\\alpha k} \\gamma \\rangle\nM_{\\beta n}T_{\\alpha k} g$ can be extended from $L^2(\\mathbb{R})$ to\n$M^q(\\mathbb{R})$ for all $f\\in M^q(\\mathbb{R})$ and all $p\\leq q\\leq p'$ with\nunconditional convergence of the series. Finally, we characterize all Gabor\nsystems $\\{M_{\\beta n}T_{\\alpha k}g\\}_{n,k\\in \\mathbb{Z}}$ in\n$M^{p,q}(\\mathbb{R})$ for any $1\\leq p,q<\\infty$ for which $f = \\sum \\langle f,\n\\gamma_{k,n} \\rangle M_{\\beta n}T_{\\alpha k} g$ with unconditional convergence\nof the series for all $f$ in $M^{p,q}(\\mathbb{R})$ and all alternative duals\n$\\{\\gamma_{k,n}\\}_{k,n\\in \\mathbb{Z}}$ of $\\{M_{\\beta n}T_{\\alpha k}\ng\\}_{n,k\\in \\mathbb{Z}}$.","PeriodicalId":501036,"journal":{"name":"arXiv - MATH - Functional Analysis","volume":"1 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"arXiv - MATH - Functional Analysis","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/arxiv-2408.16593","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
This paper consists of two parts. In the first half, we solve the question
raised by Heil as to whether the atom of a Gabor frame must be in
$M^p(\mathbb{R})$ for some $1