<p>We study the accuracy of reconstruction of a family of functions <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="38" /> </InlineMediaObject> <EquationSource Format="TEX">\(f_\epsilon (x)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>f</mi> <mi>ϵ</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq4.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="49" /> </InlineMediaObject> <EquationSource Format="TEX">\(x\in \mathbb R^2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>x</mi> <mo>∈</mo> <msup> <mi mathvariant="double-struck">R</mi> <mn>2</mn> </msup> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq5.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="43" /> </InlineMediaObject> <EquationSource Format="TEX">\(\epsilon \rightarrow 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ϵ</mi> <mo stretchy="false">→</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>, from their discrete Radon transform data sampled with step size <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq6.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="34" /> </InlineMediaObject> <EquationSource Format="TEX">\(O(\epsilon )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>O</mi> <mo stretchy="false">(</mo> <mi>ϵ</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>. For each <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq7.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="39" /> </InlineMediaObject> <EquationSource Format="TEX">\(\epsilon &gt;0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ϵ</mi> <mo>&gt;</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> sufficiently small, the function <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq8.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="17" /> </InlineMediaObject> <EquationSource Format="TEX">\(f_\epsilon \)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>f</mi> <mi>ϵ</mi> </msub> </math></EquationSource> </InlineEquation> has a jump across a rough boundary <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq9.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal S_\epsilon \)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="script">S</mi> <mi>ϵ</mi> </msub> </math></EquationSource> </InlineEquation>, which is modeled by an <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq6.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="34" /> </InlineMediaObject> <EquationSource Format="TEX">\(O(\epsilon )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>O</mi> <mo stretchy="false">(</mo> <mi>ϵ</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>-size perturbation of a smooth boundary <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq11.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal S\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">S</mi> </math></EquationSource> </InlineEquation>. The function <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq12.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="22" /> </InlineMediaObject> <EquationSource Format="TEX">\(H_0\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>H</mi> <mn>0</mn> </msub> </math></EquationSource> </InlineEquation>, which describes the perturbation, is assumed to have bounded variation. Let <InlineEquation ID="IEq13"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq13.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="28" /> </InlineMediaObject> <EquationSource Format="TEX">\(f_\epsilon ^{\text {rec}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>f</mi> <mi>ϵ</mi> <mtext>rec</mtext> </msubsup> </math></EquationSource> </InlineEquation> denote the reconstruction computed by interpolating discrete data and substituting it into a continuous inversion formula. We prove that <InlineEquation ID="IEq14"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq14.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="298" /> </InlineMediaObject> <EquationSource Format="TEX">\((f_\epsilon ^{\text {rec}}-K_\epsilon *f_\epsilon )(x_0+\epsilon \check{x})=O(\epsilon ^{1/2}\ln (1/\epsilon ))\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow> <mo stretchy="false">(</mo> <msubsup> <mi>f</mi> <mi>ϵ</mi> <mtext>rec</mtext> </msubsup> <mo>-</mo> <msub> <mi>K</mi> <mi>ϵ</mi> </msub> <mrow /> <mo>∗</mo> <msub> <mi>f</mi> <mi>ϵ</mi> </msub> <mo stretchy="false">)</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <msub> <mi>x</mi> <mn>0</mn> </msub> <mo>+</mo> <mi>ϵ</mi> <mover accent="true"> <mi>x</mi> <mo stretchy="false">ˇ</mo> </mover> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mi>O</mi> <mrow> <mo stretchy="false">(</mo> <msup> <mi>ϵ</mi> <mrow> <mn>1</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </msup> <mo>ln</mo> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo stretchy="false">/</mo> <mi>ϵ</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, where <InlineEquation ID="IEq15"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq15.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="52" /> </InlineMediaObject> <EquationSource Format="TEX">\(x_0\in \mathcal S\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>x</mi> <mn>0</mn> </msub> <mo>∈</mo> <mi mathvariant="script">S</mi> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq16"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41_2025_10175_Article_IEq16.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="22" /> </InlineMediaObject> <EquationSource Format="TEX">\(K_\epsilon \)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>K</mi> <mi>ϵ</mi> </msub> </math></EquationSource> </InlineEquation> is an easily computable kernel.</p>

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Analysis of Reconstruction of Functions with Rough Edges from Discrete Radon Data in \({\mathbb {R}}^2\)

  • Alexander Katsevich

摘要

We study the accuracy of reconstruction of a family of functions \(f_\epsilon (x)\) f ϵ ( x ) , \(x\in \mathbb R^2\) x R 2 , \(\epsilon \rightarrow 0\) ϵ 0 , from their discrete Radon transform data sampled with step size \(O(\epsilon )\) O ( ϵ ) . For each \(\epsilon >0\) ϵ > 0 sufficiently small, the function \(f_\epsilon \) f ϵ has a jump across a rough boundary \(\mathcal S_\epsilon \) S ϵ , which is modeled by an \(O(\epsilon )\) O ( ϵ ) -size perturbation of a smooth boundary \(\mathcal S\) S . The function \(H_0\) H 0 , which describes the perturbation, is assumed to have bounded variation. Let \(f_\epsilon ^{\text {rec}}\) f ϵ rec denote the reconstruction computed by interpolating discrete data and substituting it into a continuous inversion formula. We prove that \((f_\epsilon ^{\text {rec}}-K_\epsilon *f_\epsilon )(x_0+\epsilon \check{x})=O(\epsilon ^{1/2}\ln (1/\epsilon ))\) ( f ϵ rec - K ϵ f ϵ ) ( x 0 + ϵ x ˇ ) = O ( ϵ 1 / 2 ln ( 1 / ϵ ) ) , where \(x_0\in \mathcal S\) x 0 S and \(K_\epsilon \) K ϵ is an easily computable kernel.