<p>This paper addresses the time-dependent Porous Medium Equation, <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10440_2025_747_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="108" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msub> <mi>u</mi> <mi>t</mi> </msub> <mo>−</mo> <mi>α</mi> <mi mathvariant="normal">Δ</mi> <msup> <mi>u</mi> <mi>γ</mi> </msup> <mo>=</mo> <mn>0</mn> </math></EquationSource> <EquationSource Format="TEX">$u_{t} - \alpha \Delta u^{\gamma }= 0$</EquationSource> </InlineEquation> with polytropic exponent <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10440_2025_747_Article_IEq2.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="43" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>γ</mi> <mo>&gt;</mo> <mn>1</mn> </math></EquationSource> <EquationSource Format="TEX">$\gamma &gt;1$</EquationSource> </InlineEquation> and diffusion coefficient <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10440_2025_747_Article_IEq3.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="43" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>α</mi> <mo>&gt;</mo> <mn>0</mn> </math></EquationSource> <EquationSource Format="TEX">$\alpha &gt;0$</EquationSource> </InlineEquation>. Given the value of <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10440_2025_747_Article_IEq4.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>γ</mi> </math></EquationSource> <EquationSource Format="TEX">$\gamma $</EquationSource> </InlineEquation> and the solution <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10440_2025_747_Article_IEq5.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>u</mi> </math></EquationSource> <EquationSource Format="TEX">$u$</EquationSource> </InlineEquation> at a large time <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10440_2025_747_Article_IEq6.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>T</mi> </math></EquationSource> <EquationSource Format="TEX">$T$</EquationSource> </InlineEquation>, our goal is to determine the parameter <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10440_2025_747_Article_IEq7.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>α</mi> </math></EquationSource> <EquationSource Format="TEX">$\alpha $</EquationSource> </InlineEquation> without the knowledge of the initial data <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10440_2025_747_Article_IEq8.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="31" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>u</mi> <mo stretchy="false">(</mo> <mn>0</mn> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$u(0)$</EquationSource> </InlineEquation>. Leveraging an asymptotic inequality satisfied by <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10440_2025_747_Article_IEq9.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="36" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>u</mi> <mo stretchy="false">(</mo> <mi>T</mi> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$u(T)$</EquationSource> </InlineEquation>, we propose a numerical algorithm to recover <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10440_2025_747_Article_IEq7.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>α</mi> </math></EquationSource> <EquationSource Format="TEX">$\alpha $</EquationSource> </InlineEquation> through a minimization problem. Furthermore, we establish an upper bound on the error between the exact and recovered values of <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10440_2025_747_Article_IEq7.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>α</mi> </math></EquationSource> <EquationSource Format="TEX">$\alpha $</EquationSource> </InlineEquation> and perform numerical simulations in two and three dimensional cases.</p>

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Recovering the Diffusion Coefficient in the Porous Medium Equation from a Large-Time Measurement

  • Hagop Karakazian,
  • Toni Sayah,
  • Faouzi Triki

摘要

This paper addresses the time-dependent Porous Medium Equation, u t α Δ u γ = 0 $u_{t} - \alpha \Delta u^{\gamma }= 0$ with polytropic exponent γ > 1 $\gamma >1$ and diffusion coefficient α > 0 $\alpha >0$ . Given the value of γ $\gamma $ and the solution u $u$ at a large time T $T$ , our goal is to determine the parameter α $\alpha $ without the knowledge of the initial data u ( 0 ) $u(0)$ . Leveraging an asymptotic inequality satisfied by u ( T ) $u(T)$ , we propose a numerical algorithm to recover α $\alpha $ through a minimization problem. Furthermore, we establish an upper bound on the error between the exact and recovered values of α $\alpha $ and perform numerical simulations in two and three dimensional cases.