<p>We discuss the boundedness of the cone-like restricted maximal operator of two-dimensional Nörlund means from the dyadic Hardy space <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_818_Article_IEq1.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">\(H^\gamma _p({\mathbb I}^2)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi>H</mi> <mi>p</mi> <mi>γ</mi> </msubsup> <mrow> <mo stretchy="false">(</mo> <msup> <mrow> <mi mathvariant="double-struck">I</mi> </mrow> <mn>2</mn> </msup> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> to the Lebesgue space <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_818_Article_IEq2.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="43" /> </InlineMediaObject> <EquationSource Format="TEX">\(L_p({\mathbb I}^2)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>L</mi> <mi>p</mi> </msub> <mrow> <mo stretchy="false">(</mo> <msup> <mrow> <mi mathvariant="double-struck">I</mi> </mrow> <mn>2</mn> </msup> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>. The results are formulated for monotone non-increasing and monotone non-decreasing generating sequences of the Nörlund means. We give a necessary and sufficient condition for the boundedness of the cone-like restricted maximal operator of two-dimensional Nörlund means from the dyadic Hardy space <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_818_Article_IEq1.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">\(H^\gamma _p({\mathbb I}^2)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi>H</mi> <mi>p</mi> <mi>γ</mi> </msubsup> <mrow> <mo stretchy="false">(</mo> <msup> <mrow> <mi mathvariant="double-struck">I</mi> </mrow> <mn>2</mn> </msup> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> to the Lebesgue space <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_818_Article_IEq2.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="43" /> </InlineMediaObject> <EquationSource Format="TEX">\(L_p({\mathbb I}^2)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>L</mi> <mi>p</mi> </msub> <mrow> <mo stretchy="false">(</mo> <msup> <mrow> <mi mathvariant="double-struck">I</mi> </mrow> <mn>2</mn> </msup> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> (<InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_818_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="88" /> </InlineMediaObject> <EquationSource Format="TEX">\(1/2&lt;p\leqslant 1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1</mn> <mo stretchy="false">/</mo> <mn>2</mn> <mo>&lt;</mo> <mi>p</mi> <mo>⩽</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation>), when both of the generating sequences are monotone non-increasing. The almost everywhere convergence of the two-dimensional Nörlund means is proved under certain assumptions in the case when its indices belong to some positive cone-like set around the function <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_818_Article_IEq6.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\gamma \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>γ</mi> </math></EquationSource> </InlineEquation>.</p>

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Restricted convergence of two-dimensional Nörlund means of Walsh–Fourier series

  • Károly Nagy

摘要

We discuss the boundedness of the cone-like restricted maximal operator of two-dimensional Nörlund means from the dyadic Hardy space \(H^\gamma _p({\mathbb I}^2)\) H p γ ( I 2 ) to the Lebesgue space \(L_p({\mathbb I}^2)\) L p ( I 2 ) . The results are formulated for monotone non-increasing and monotone non-decreasing generating sequences of the Nörlund means. We give a necessary and sufficient condition for the boundedness of the cone-like restricted maximal operator of two-dimensional Nörlund means from the dyadic Hardy space \(H^\gamma _p({\mathbb I}^2)\) H p γ ( I 2 ) to the Lebesgue space \(L_p({\mathbb I}^2)\) L p ( I 2 ) ( \(1/2<p\leqslant 1\) 1 / 2 < p 1 ), when both of the generating sequences are monotone non-increasing. The almost everywhere convergence of the two-dimensional Nörlund means is proved under certain assumptions in the case when its indices belong to some positive cone-like set around the function \(\gamma \) γ .