<p>In this paper we study the Cauchy problem for semilinear parabolic system with nonconstant coefficient singular initial data <Equation ID="Equ81"> <EquationSource Format="TEX">\(\begin{aligned} {\left\{ \begin{array}{ll} U_{t}-\Delta U=\mu _{1}|U|^{p-1}U+\beta |U|^{r-1}U|V|^{r+1},&amp; x\in \mathbb {R}^{N},t&gt;0, \\ V_{t}-\Delta V=\mu _{2}|V|^{p-1}V+\beta |U|^{r+1}|V|^{r-1}V,&amp; x\in \mathbb {R}^{N},t&gt;0, \\ U(x,0)=\lambda _{1} a(x/|x|)|x|^{-2/(p-1)},&amp; x\in \mathbb {R}^{N}\setminus \{0\},\\ V(x,0)=\lambda _{2} b(x/|x|)|x|^{-2/(p-1)},&amp; x\in \mathbb {R}^{N}\setminus \{0\},\\ \end{array}\right. } \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mfenced open="{"> <mrow> <mtable> <mtr> <mtd columnalign="left"> <mrow> <msub> <mi>U</mi> <mi>t</mi> </msub> <mo>-</mo> <mi mathvariant="normal">Δ</mi> <mi>U</mi> <mo>=</mo> <msub> <mi>μ</mi> <mn>1</mn> </msub> <msup> <mrow> <mo stretchy="false">|</mo> <mi>U</mi> <mo stretchy="false">|</mo> </mrow> <mrow> <mi>p</mi> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mi>U</mi> <mo>+</mo> <msup> <mrow> <mi>β</mi> <mo stretchy="false">|</mo> <mi>U</mi> <mo stretchy="false">|</mo> </mrow> <mrow> <mi>r</mi> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mi>U</mi> <msup> <mrow> <mo stretchy="false">|</mo> <mi>V</mi> <mo stretchy="false">|</mo> </mrow> <mrow> <mi>r</mi> <mo>+</mo> <mn>1</mn> </mrow> </msup> <mo>,</mo> </mrow> </mtd> <mtd columnalign="left"> <mrow> <mi>x</mi> <mo>∈</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>N</mi> </msup> <mo>,</mo> <mi>t</mi> <mo>&gt;</mo> <mn>0</mn> <mo>,</mo> </mrow> </mtd> </mtr> <mtr> <mtd columnalign="left"> <mrow> <mrow /> <msub> <mi>V</mi> <mi>t</mi> </msub> <mo>-</mo> <mi mathvariant="normal">Δ</mi> <mi>V</mi> <mo>=</mo> <msub> <mi>μ</mi> <mn>2</mn> </msub> <msup> <mrow> <mo stretchy="false">|</mo> <mi>V</mi> <mo stretchy="false">|</mo> </mrow> <mrow> <mi>p</mi> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mi>V</mi> <mo>+</mo> <msup> <mrow> <mi>β</mi> <mo stretchy="false">|</mo> <mi>U</mi> <mo stretchy="false">|</mo> </mrow> <mrow> <mi>r</mi> <mo>+</mo> <mn>1</mn> </mrow> </msup> <msup> <mrow> <mo stretchy="false">|</mo> <mi>V</mi> <mo stretchy="false">|</mo> </mrow> <mrow> <mi>r</mi> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mi>V</mi> <mo>,</mo> </mrow> </mtd> <mtd columnalign="left"> <mrow> <mi>x</mi> <mo>∈</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>N</mi> </msup> <mo>,</mo> <mi>t</mi> <mo>&gt;</mo> <mn>0</mn> <mo>,</mo> </mrow> </mtd> </mtr> <mtr> <mtd columnalign="left"> <mrow> <mrow /> <mi>U</mi> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo>,</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <msub> <mi>λ</mi> <mn>1</mn> </msub> <msup> <mrow> <mi>a</mi> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">/</mo> <mo stretchy="false">|</mo> <mi>x</mi> <mo stretchy="false">|</mo> <mo stretchy="false">)</mo> <mo stretchy="false">|</mo> <mi>x</mi> <mo stretchy="false">|</mo> </mrow> <mrow> <mo>-</mo> <mn>2</mn> <mo stretchy="false">/</mo> <mo stretchy="false">(</mo> <mi>p</mi> <mo>-</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </msup> <mo>,</mo> </mrow> </mtd> <mtd columnalign="left"> <mrow> <mi>x</mi> <mo>∈</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>N</mi> </msup> <mo lspace="0.15em" rspace="0.15em" stretchy="false">\</mo> <mrow> <mo stretchy="false">{</mo> <mn>0</mn> <mo stretchy="false">}</mo> </mrow> <mo>,</mo> </mrow> </mtd> </mtr> <mtr> <mtd columnalign="left"> <mrow> <mrow /> <mi>V</mi> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo>,</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <msub> <mi>λ</mi> <mn>2</mn> </msub> <msup> <mrow> <mi>b</mi> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">/</mo> <mo stretchy="false">|</mo> <mi>x</mi> <mo stretchy="false">|</mo> <mo stretchy="false">)</mo> <mo stretchy="false">|</mo> <mi>x</mi> <mo stretchy="false">|</mo> </mrow> <mrow> <mo>-</mo> <mn>2</mn> <mo stretchy="false">/</mo> <mo stretchy="false">(</mo> <mi>p</mi> <mo>-</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </msup> <mo>,</mo> </mrow> </mtd> <mtd columnalign="left"> <mrow> <mi>x</mi> <mo>∈</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>N</mi> </msup> <mo lspace="0.15em" rspace="0.15em" stretchy="false">\</mo> <mrow> <mo stretchy="false">{</mo> <mn>0</mn> <mo stretchy="false">}</mo> </mrow> <mo>,</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </mfenced> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>where <InlineEquation ID="IEq1"> <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="IEq2"> <EquationSource Format="TEX">\(p=2r+1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>=</mo> <mn>2</mn> <mi>r</mi> <mo>+</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\mu _{1},\mu _{2},\beta &gt;0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>μ</mi> <mn>1</mn> </msub> <mo>,</mo> <msub> <mi>μ</mi> <mn>2</mn> </msub> <mo>,</mo> <mi>β</mi> <mo>&gt;</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\lambda _{1},\lambda _{2}&gt;0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>λ</mi> <mn>1</mn> </msub> <mo>,</mo> <msub> <mi>λ</mi> <mn>2</mn> </msub> <mo>&gt;</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> are constant parameters, <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(a\ge 0\not \equiv 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>a</mi> <mo>≥</mo> <mn>0</mn> <mo>≢</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(b\ge 0\not \equiv 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>b</mi> <mo>≥</mo> <mn>0</mn> <mo>≢</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>. We demonstrate that when <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(2&lt;N(p-1)&lt;2(p+1)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>2</mn> <mo>&lt;</mo> <mi>N</mi> <mo stretchy="false">(</mo> <mi>p</mi> <mo>-</mo> <mn>1</mn> <mo stretchy="false">)</mo> <mo>&lt;</mo> <mn>2</mn> <mo stretchy="false">(</mo> <mi>p</mi> <mo>+</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(p=(N+2)/(N-2)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>=</mo> <mo stretchy="false">(</mo> <mi>N</mi> <mo>+</mo> <mn>2</mn> <mo stretchy="false">)</mo> <mo stretchy="false">/</mo> <mo stretchy="false">(</mo> <mi>N</mi> <mo>-</mo> <mn>2</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, the system has two positive self-similar solutions <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\((\underline{u}_{\lambda _{1}},\underline{v}_{\lambda _{2}})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <msub> <munder> <mi>u</mi> <mo>̲</mo> </munder> <msub> <mi>λ</mi> <mn>1</mn> </msub> </msub> <mo>,</mo> <msub> <munder> <mi>v</mi> <mo>̲</mo> </munder> <msub> <mi>λ</mi> <mn>2</mn> </msub> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\((\overline{u}_{\lambda _{1}},\overline{v}_{\lambda _{2}})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <msub> <mover> <mi>u</mi> <mo>¯</mo> </mover> <msub> <mi>λ</mi> <mn>1</mn> </msub> </msub> <mo>,</mo> <msub> <mover> <mi>v</mi> <mo>¯</mo> </mover> <msub> <mi>λ</mi> <mn>2</mn> </msub> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> if <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(\lambda _{1}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>λ</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(\lambda _{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>λ</mi> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation> are small enough. Additionally, there are no positive self-similar solutions if <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(\lambda _{1},\lambda _{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>λ</mi> <mn>1</mn> </msub> <mo>,</mo> <msub> <mi>λ</mi> <mn>2</mn> </msub> </mrow> </math></EquationSource> </InlineEquation> are sufficiently large.</p>

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Existence and multiplicity of self-similar positive solutions for the parabolic system with singular initial data

  • Xuan Wang,
  • Jun Wang

摘要

In this paper we study the Cauchy problem for semilinear parabolic system with nonconstant coefficient singular initial data \(\begin{aligned} {\left\{ \begin{array}{ll} U_{t}-\Delta U=\mu _{1}|U|^{p-1}U+\beta |U|^{r-1}U|V|^{r+1},& x\in \mathbb {R}^{N},t>0, \\ V_{t}-\Delta V=\mu _{2}|V|^{p-1}V+\beta |U|^{r+1}|V|^{r-1}V,& x\in \mathbb {R}^{N},t>0, \\ U(x,0)=\lambda _{1} a(x/|x|)|x|^{-2/(p-1)},& x\in \mathbb {R}^{N}\setminus \{0\},\\ V(x,0)=\lambda _{2} b(x/|x|)|x|^{-2/(p-1)},& x\in \mathbb {R}^{N}\setminus \{0\},\\ \end{array}\right. } \end{aligned}\) U t - Δ U = μ 1 | U | p - 1 U + β | U | r - 1 U | V | r + 1 , x R N , t > 0 , V t - Δ V = μ 2 | V | p - 1 V + β | U | r + 1 | V | r - 1 V , x R N , t > 0 , U ( x , 0 ) = λ 1 a ( x / | x | ) | x | - 2 / ( p - 1 ) , x R N \ { 0 } , V ( x , 0 ) = λ 2 b ( x / | x | ) | x | - 2 / ( p - 1 ) , x R N \ { 0 } , where \(N\ge 2\) N 2 , \(p=2r+1\) p = 2 r + 1 , \(\mu _{1},\mu _{2},\beta >0\) μ 1 , μ 2 , β > 0 , \(\lambda _{1},\lambda _{2}>0\) λ 1 , λ 2 > 0 are constant parameters, \(a\ge 0\not \equiv 0\) a 0 0 , \(b\ge 0\not \equiv 0\) b 0 0 . We demonstrate that when \(2<N(p-1)<2(p+1)\) 2 < N ( p - 1 ) < 2 ( p + 1 ) and \(p=(N+2)/(N-2)\) p = ( N + 2 ) / ( N - 2 ) , the system has two positive self-similar solutions \((\underline{u}_{\lambda _{1}},\underline{v}_{\lambda _{2}})\) ( u ̲ λ 1 , v ̲ λ 2 ) and \((\overline{u}_{\lambda _{1}},\overline{v}_{\lambda _{2}})\) ( u ¯ λ 1 , v ¯ λ 2 ) if \(\lambda _{1}\) λ 1 and \(\lambda _{2}\) λ 2 are small enough. Additionally, there are no positive self-similar solutions if \(\lambda _{1},\lambda _{2}\) λ 1 , λ 2 are sufficiently large.