<p>In this paper, we consider the following nonlinear parabolic equation <Equation ID="Equ64"> <EquationSource Format="TEX">\( \partial _{t}u\,=\,\sum _{i=1}^{n}\partial _{x_{i}}\left[ (\vert u_{x_{i}}\vert -\delta _{i})_{+}^{p-1}\frac{u_{x_{i}}}{\vert u_{x_{i}}\vert }\right] \,\,\,\,\,\,\,\,\,\,\textrm{in}\,\,\,\Omega \times I, \)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <msub> <mi>∂</mi> <mi>t</mi> </msub> <mi>u</mi> <mspace width="0.166667em" /> <mo>=</mo> <mspace width="0.166667em" /> <munderover> <mo>∑</mo> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </munderover> <msub> <mi>∂</mi> <msub> <mi>x</mi> <mi>i</mi> </msub> </msub> <mfenced close="]" open="["> <mrow> <mo stretchy="false">(</mo> <mo stretchy="false">|</mo> </mrow> <msub> <mi>u</mi> <msub> <mi>x</mi> <mi>i</mi> </msub> </msub> <msubsup> <mrow> <mo stretchy="false">|</mo> <mo>-</mo> <msub> <mi>δ</mi> <mi>i</mi> </msub> <mo stretchy="false">)</mo> </mrow> <mrow> <mo>+</mo> </mrow> <mrow> <mi>p</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mfrac> <msub> <mi>u</mi> <msub> <mi>x</mi> <mi>i</mi> </msub> </msub> <mrow> <mrow> <mo stretchy="false">|</mo> </mrow> <msub> <mi>u</mi> <msub> <mi>x</mi> <mi>i</mi> </msub> </msub> <mrow> <mo stretchy="false">|</mo> </mrow> </mrow> </mfrac> </mfenced> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mtext>in</mtext> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mi mathvariant="normal">Ω</mi> <mo>×</mo> <mi>I</mi> <mo>,</mo> </mrow> </math></EquationSource> </Equation>where <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\Omega \)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">Ω</mi> </math></EquationSource> </InlineEquation> is a bounded open subset of <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\mathbb {R}^{n}\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>n</mi> </msup> </math></EquationSource> </InlineEquation> for <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(n\ge 2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>n</mi> <mo>≥</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(I\subset \mathbb {R}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>I</mi> <mo>⊂</mo> <mi mathvariant="double-struck">R</mi> </mrow> </math></EquationSource> </InlineEquation> is a bounded open interval, <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(p\ge 2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>≥</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\delta _{1},\ldots ,\delta _{n}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>δ</mi> <mn>1</mn> </msub> <mo>,</mo> <mo>…</mo> <mo>,</mo> <msub> <mi>δ</mi> <mi>n</mi> </msub> </mrow> </math></EquationSource> </InlineEquation> are non-negative numbers and <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\left( \,\cdot \,\right) _{+}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mfenced close=")" open="("> <mspace width="0.166667em" /> <mo>·</mo> <mspace width="0.166667em" /> </mfenced> <mo>+</mo> </msub> </math></EquationSource> </InlineEquation> denotes the positive part. We prove that the local weak solutions are locally Lipschitz continuous in the spatial variable. The main novelty here is that the above equation combines an orthotropic structure with a strongly degenerate behavior. We emphasize that our result can be considered, on the one hand, as the parabolic counterpart of the elliptic result established in [<CitationRef CitationID="CR12">12</CitationRef>], and on the other hand as an extension to a significantly more degenerate framework of the findings contained in [<CitationRef CitationID="CR13">13</CitationRef>].</p>

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Gradient bounds for a widely degenerate orthotropic parabolic equation

  • Pasquale Ambrosio

摘要

In this paper, we consider the following nonlinear parabolic equation \( \partial _{t}u\,=\,\sum _{i=1}^{n}\partial _{x_{i}}\left[ (\vert u_{x_{i}}\vert -\delta _{i})_{+}^{p-1}\frac{u_{x_{i}}}{\vert u_{x_{i}}\vert }\right] \,\,\,\,\,\,\,\,\,\,\textrm{in}\,\,\,\Omega \times I, \) t u = i = 1 n x i ( | u x i | - δ i ) + p - 1 u x i | u x i | in Ω × I , where \(\Omega \) Ω is a bounded open subset of \(\mathbb {R}^{n}\) R n for \(n\ge 2\) n 2 , \(I\subset \mathbb {R}\) I R is a bounded open interval, \(p\ge 2\) p 2 , \(\delta _{1},\ldots ,\delta _{n}\) δ 1 , , δ n are non-negative numbers and \(\left( \,\cdot \,\right) _{+}\) · + denotes the positive part. We prove that the local weak solutions are locally Lipschitz continuous in the spatial variable. The main novelty here is that the above equation combines an orthotropic structure with a strongly degenerate behavior. We emphasize that our result can be considered, on the one hand, as the parabolic counterpart of the elliptic result established in [12], and on the other hand as an extension to a significantly more degenerate framework of the findings contained in [13].