<p>For a nonnegative nondecreasing unbounded right-continuous function <i>F</i> on [0, +∞), an entire transcendental function <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(f\left(z\right)={\sum }_{k=0}^{\infty }{f}_{k}{z}^{k}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mfenced close=")" open="("> <mi>z</mi> </mfenced> <mo>=</mo> <msubsup> <mo>∑</mo> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> <mi>∞</mi> </msubsup> <msub> <mi>f</mi> <mi>k</mi> </msub> <msup> <mrow> <mi>z</mi> </mrow> <mi>k</mi> </msup> </mrow> </math></EquationSource> </InlineEquation> with <i>f</i><sub><i>k</i></sub> ≥ 0 for all <i>t</i> ≥ 0, and a function <i>a</i>(<i>x</i>) nonnegative on [0, +∞), the integral <i>I</i>(<i>r</i>) = <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({\int }_{0}^{\infty }a\left(x\right)f\left(xr\right)dF\left(x\right)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mo>∫</mo> <mrow> <mn>0</mn> </mrow> <mi>∞</mi> </msubsup> <mi>a</mi> <mfenced close=")" open="("> <mi>x</mi> </mfenced> <mi>f</mi> <mfenced close=")" open="("> <mi>x</mi> <mi>r</mi> </mfenced> <mi>d</mi> <mi>F</mi> <mfenced close=")" open="("> <mi>x</mi> </mfenced> </mrow> </math></EquationSource> </InlineEquation> is called a Laplace–Stieltjes-type integral. Suppose that for a positive function Φ unbounded on (–∞, +∞), the derivative Φ<sup>′</sup> is a positive continuously differentiable function increasing to +∞. We establish the conditions under which the following relation is true: <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\({\int }_{{r}_{0}}^{\infty }\frac{{\Phi }^{\prime}\left(r\right)\mathrm{ln}I\left(r\right)}{{\Phi }^{2}\left(r\right)}dr&lt;+\infty \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mo>∫</mo> <mrow> <msub> <mi>r</mi> <mn>0</mn> </msub> </mrow> <mi>∞</mi> </msubsup> <mfrac> <mrow> <msup> <mrow> <mi mathvariant="normal">Φ</mi> </mrow> <mo>′</mo> </msup> <mfenced close=")" open="("> <mi>r</mi> </mfenced> <mi mathvariant="normal">ln</mi> <mi>I</mi> <mfenced close=")" open="("> <mi>r</mi> </mfenced> </mrow> <mrow> <msup> <mrow> <mi mathvariant="normal">Φ</mi> </mrow> <mn>2</mn> </msup> <mfenced close=")" open="("> <mi>r</mi> </mfenced> </mrow> </mfrac> <mi>d</mi> <mi>r</mi> <mo>&lt;</mo> <mo>+</mo> <mi>∞</mi> </mrow> </math></EquationSource> </InlineEquation>.</p>

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Belonging of Laplace–Stieltjes-Type Integrals to the Convergence Φ-Class

  • O. M. Mulyava,
  • M. M. Sheremeta,
  • Yu. S. Trukhan

摘要

For a nonnegative nondecreasing unbounded right-continuous function F on [0, +∞), an entire transcendental function \(f\left(z\right)={\sum }_{k=0}^{\infty }{f}_{k}{z}^{k}\) f z = k = 0 f k z k with fk ≥ 0 for all t ≥ 0, and a function a(x) nonnegative on [0, +∞), the integral I(r) = \({\int }_{0}^{\infty }a\left(x\right)f\left(xr\right)dF\left(x\right)\) 0 a x f x r d F x is called a Laplace–Stieltjes-type integral. Suppose that for a positive function Φ unbounded on (–∞, +∞), the derivative Φ is a positive continuously differentiable function increasing to +∞. We establish the conditions under which the following relation is true: \({\int }_{{r}_{0}}^{\infty }\frac{{\Phi }^{\prime}\left(r\right)\mathrm{ln}I\left(r\right)}{{\Phi }^{2}\left(r\right)}dr<+\infty \) r 0 Φ r ln I r Φ 2 r d r < + .