<p>In the space of 2π-periodic functions <i>L</i><sub>2</sub><i>,</i> we study the characteristic of smoothness <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11253_2025_2443_Article_IEq1.gif" Format="GIF" Height="24" Rendition="HTML" Resolution="72" Type="Linedraw" Width="240" /> </InlineMediaObject> <EquationSource Format="TEX">\({\omega }_{\mathcal{M}}^{*}\left(f,t\right) :=\left(1/t\right){\int }_{0}^{t}\omega \mathcal{M}\left(f,\tau \right)d\tau \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mi>ω</mi> <mrow> <mi mathvariant="script">M</mi> </mrow> <mrow> <mrow /> <mo>∗</mo> </mrow> </mmultiscripts> <mfenced close=")" open="("> <mi>f</mi> <mo>,</mo> <mi>t</mi> </mfenced> <mo>:</mo> <mo>=</mo> <mfenced close=")" open="("> <mn>1</mn> <mo stretchy="false">/</mo> <mi>t</mi> </mfenced> <msubsup> <mo>∫</mo> <mrow> <mn>0</mn> </mrow> <mi>t</mi> </msubsup> <mi>ω</mi> <mi mathvariant="script">M</mi> <mfenced close=")" open="("> <mi>f</mi> <mo>,</mo> <mi>τ</mi> </mfenced> <mi>d</mi> <mi>τ</mi> </mrow> </math></EquationSource> </InlineEquation> obtained as a result of averaging of the generalized modulus of continuity ω<sub>ℳ</sub>(<i>f</i>) formed by using a generalized finite-difference operator <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11253_2025_2443_Article_IEq2.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="111" /> </InlineMediaObject> <EquationSource Format="TEX">\({\Delta }_{h}^{\mathcal{M}}: {L}_{2}\to {L}_{2}.\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi mathvariant="normal">Δ</mi> <mrow> <mi>h</mi> </mrow> <mi mathvariant="script">M</mi> </msubsup> <mo>:</mo> <msub> <mi>L</mi> <mn>2</mn> </msub> <mo stretchy="false">→</mo> <msub> <mi>L</mi> <mn>2</mn> </msub> <mo>.</mo> </mrow> </math></EquationSource> </InlineEquation> We also study some properties of the functions ω<sub>ℳ</sub>(<i>f</i>) and <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11253_2025_2443_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="60" /> </InlineMediaObject> <EquationSource Format="TEX">\({\omega }_{\mathcal{M}}^{*}\left(f\right).\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mi>ω</mi> <mrow> <mi mathvariant="script">M</mi> </mrow> <mrow> <mrow /> <mo>∗</mo> </mrow> </mmultiscripts> <mfenced close=")" open="("> <mi>f</mi> </mfenced> <mo>.</mo> </mrow> </math></EquationSource> </InlineEquation> For the classes of functions <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11253_2025_2443_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="87" /> </InlineMediaObject> <EquationSource Format="TEX">\(W\left({\omega }_{\mathcal{M}}^{*},\Phi \right),\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>W</mi> <mfenced close=")" open="("> <mmultiscripts> <mi>ω</mi> <mrow> <mi mathvariant="script">M</mi> </mrow> <mrow> <mrow /> <mo>∗</mo> </mrow> </mmultiscripts> <mo>,</mo> <mi mathvariant="normal">Φ</mi> </mfenced> <mo>,</mo> </mrow> </math></EquationSource> </InlineEquation> where Φ is a majorant, we determine the lower and upper estimates for the values of a series of <i>n</i>-widths and establish the condition for Φ under which the exact values of these estimates are obtained. Several exact results are illustrated by specific examples.</p>

错误:搜索内容不能为空,请输入英文关键词
错误:关键词超出字数限制,请精简
高级检索

Averaged Characteristics of Smoothness in L2 and Estimations for the Values of Widths of Function Classes

  • Serhii Vakarchuk,
  • Valentyna Zabutna,
  • Mykhailo Vakarchuk

摘要

In the space of 2π-periodic functions L2, we study the characteristic of smoothness \({\omega }_{\mathcal{M}}^{*}\left(f,t\right) :=\left(1/t\right){\int }_{0}^{t}\omega \mathcal{M}\left(f,\tau \right)d\tau \) ω M f , t : = 1 / t 0 t ω M f , τ d τ obtained as a result of averaging of the generalized modulus of continuity ω(f) formed by using a generalized finite-difference operator \({\Delta }_{h}^{\mathcal{M}}: {L}_{2}\to {L}_{2}.\) Δ h M : L 2 L 2 . We also study some properties of the functions ω(f) and \({\omega }_{\mathcal{M}}^{*}\left(f\right).\) ω M f . For the classes of functions \(W\left({\omega }_{\mathcal{M}}^{*},\Phi \right),\) W ω M , Φ , where Φ is a majorant, we determine the lower and upper estimates for the values of a series of n-widths and establish the condition for Φ under which the exact values of these estimates are obtained. Several exact results are illustrated by specific examples.