<p>In this paper, we introduce and study a broad class of semi-discrete sampling operators, namely Durrmeyer-type sampling operators <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\( M^{\eta ,\uptau }_{w,\nu } \)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>M</mi> <mrow> <mi>w</mi> <mo>,</mo> <mi>ν</mi> </mrow> <mrow> <mi>η</mi> <mo>,</mo> <mi mathvariant="normal">τ</mi> </mrow> </msubsup> </math></EquationSource> </InlineEquation>, constructed with respect to a non-negative, locally finite, and non-trivial Borel measure <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\( \nu \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>ν</mi> </math></EquationSource> </InlineEquation> on <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\( \mathbb {R} \)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="double-struck">R</mi> </math></EquationSource> </InlineEquation>, together with a kernel <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\( \eta \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>η</mi> </math></EquationSource> </InlineEquation> and an auxiliary weight function <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\( \uptau \)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">τ</mi> </math></EquationSource> </InlineEquation>. This formulation provides a unified framework encompassing weighted and non-uniform sampling scheme. For every locally finite measure <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\( \nu \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>ν</mi> </math></EquationSource> </InlineEquation>, we establish the fundamental approximation results such as point-wise and uniform convergence on compact subsets of <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\mathbb {R}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="double-struck">R</mi> </math></EquationSource> </InlineEquation> for bounded and uniformly continuous functions. Under an additional admissibility assumption on <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\( \nu \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>ν</mi> </math></EquationSource> </InlineEquation>, namely quasi-invariance up to a constant multiple under affine transformations, bounded Radon–Nikodým derivative, or absolute continuity with bounded density, we establish the <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(L^p(\nu )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>L</mi> <mi>p</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi>ν</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>-boundedness and convergence in the <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(L^p(\nu )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>L</mi> <mi>p</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi>ν</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>-norm for <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(1\le p\le \infty \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1</mn> <mo>≤</mo> <mi>p</mi> <mo>≤</mo> <mi>∞</mi> </mrow> </math></EquationSource> </InlineEquation>. We also provide explicit conditions ensuring self-adjointness of operators <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(M^{\eta ,\uptau }_{w,\nu }\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>M</mi> <mrow> <mi>w</mi> <mo>,</mo> <mi>ν</mi> </mrow> <mrow> <mi>η</mi> <mo>,</mo> <mi mathvariant="normal">τ</mi> </mrow> </msubsup> </math></EquationSource> </InlineEquation> in <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(L^2(\nu ).\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>L</mi> <mn>2</mn> </msup> <mrow> <mo stretchy="false">(</mo> <mi>ν</mi> <mo stretchy="false">)</mo> </mrow> <mo>.</mo> </mrow> </math></EquationSource> </InlineEquation></p>

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Convergence of Durrmeyer-Type Sampling Operators with Respect to Admissible Measures

  • Pooja Gupta,
  • Shivam Bajpeyi

摘要

In this paper, we introduce and study a broad class of semi-discrete sampling operators, namely Durrmeyer-type sampling operators \( M^{\eta ,\uptau }_{w,\nu } \) M w , ν η , τ , constructed with respect to a non-negative, locally finite, and non-trivial Borel measure \( \nu \) ν on \( \mathbb {R} \) R , together with a kernel \( \eta \) η and an auxiliary weight function \( \uptau \) τ . This formulation provides a unified framework encompassing weighted and non-uniform sampling scheme. For every locally finite measure \( \nu \) ν , we establish the fundamental approximation results such as point-wise and uniform convergence on compact subsets of \(\mathbb {R}\) R for bounded and uniformly continuous functions. Under an additional admissibility assumption on \( \nu \) ν , namely quasi-invariance up to a constant multiple under affine transformations, bounded Radon–Nikodým derivative, or absolute continuity with bounded density, we establish the \(L^p(\nu )\) L p ( ν ) -boundedness and convergence in the \(L^p(\nu )\) L p ( ν ) -norm for \(1\le p\le \infty \) 1 p . We also provide explicit conditions ensuring self-adjointness of operators \(M^{\eta ,\uptau }_{w,\nu }\) M w , ν η , τ in \(L^2(\nu ).\) L 2 ( ν ) .