<p>In the paper, we give direct and inverse approximation theorems for functions defined on semiaxis and Mellin translation in appropriate <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(L^2\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>L</mi> <mn>2</mn> </msup> </math></EquationSource> </InlineEquation> type space. The direct result is weaker than Jackson’s inequality, while inverse ones have a sharpened Timan-Zygmund forms. As a corollary, we obtain several equivalence statements generalizing Titchmarsh equivalence theorem. Some conditions of weighted integrability of Mellin transform are discussed and their sharpness is proved under some restrictions.</p>

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Approximation theorems and integrability problems in Mellin analysis

  • Nadezhda Sergeeva,
  • Sergey Volosivets

摘要

In the paper, we give direct and inverse approximation theorems for functions defined on semiaxis and Mellin translation in appropriate \(L^2\) L 2 type space. The direct result is weaker than Jackson’s inequality, while inverse ones have a sharpened Timan-Zygmund forms. As a corollary, we obtain several equivalence statements generalizing Titchmarsh equivalence theorem. Some conditions of weighted integrability of Mellin transform are discussed and their sharpness is proved under some restrictions.