<p>In this work, we investigate the following Keller–Segel system with nonlinear sensitivity and flux limitation <Equation ID="Equ43"> <EquationSource Format="TEX">\(\begin{aligned} {\left\{ \begin{array}{ll} \begin{array}{lll} u_t=\Delta u-\nabla \cdot \left( \frac{f(u)\nabla v}{(1+|\nabla v|^2)^\frac{\beta }{2}} \right) ,&amp;x \in \Omega , t&gt;0, 0=\Delta v-\mu +u,&amp;x \in \Omega , t&gt;0, \end{array} \end{array}\right. } \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mfenced open="{"> <mrow> <mtable> <mtr> <mtd columnalign="left"> <mrow> <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> <mi mathvariant="normal">∇</mi> <mo>·</mo> <mfenced close=")" open="("> <mfrac> <mrow> <mi>f</mi> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> <mi mathvariant="normal">∇</mi> <mi>v</mi> </mrow> <mrow> <msup> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mo stretchy="false">|</mo> <mi mathvariant="normal">∇</mi> <mi>v</mi> <mo stretchy="false">|</mo> </mrow> <mn>2</mn> </msup> <msup> <mrow> <mo stretchy="false">)</mo> </mrow> <mfrac> <mi>β</mi> <mn>2</mn> </mfrac> </msup> </mrow> </mfrac> </mfenced> <mo>,</mo> </mrow> </mtd> <mtd columnalign="left"> <mrow> <mi>x</mi> <mo>∈</mo> <mi mathvariant="normal">Ω</mi> <mo>,</mo> <mi>t</mi> <mo>&gt;</mo> <mn>0</mn> <mo>,</mo> <mn>0</mn> <mo>=</mo> <mi mathvariant="normal">Δ</mi> <mi>v</mi> <mo>-</mo> <mi>μ</mi> <mo>+</mo> <mi>u</mi> <mo>,</mo> </mrow> </mtd> <mtd columnalign="left"> <mrow> <mi>x</mi> <mo>∈</mo> <mi mathvariant="normal">Ω</mi> <mo>,</mo> <mi>t</mi> <mo>&gt;</mo> <mn>0</mn> <mo>,</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </mtd> </mtr> </mtable> </mrow> </mfenced> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>under homogeneous Neumann-type boundary conditions in a bounded domain <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\Omega \subset \mathbb {R}^n (n \ge 2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Ω</mi> <mo>⊂</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>n</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi>n</mi> <mo>≥</mo> <mn>2</mn> </mrow> </mrow> </math></EquationSource> </InlineEquation>), where <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\beta \in (0, 1]\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>β</mi> <mo>∈</mo> <mo stretchy="false">(</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo stretchy="false">]</mo> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\( \mu :=\frac{1}{|\Omega |} \int _{\Omega } u_0(x) \,\textrm{d}x \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>μ</mi> <mo>:</mo> <mo>=</mo> <mfrac> <mn>1</mn> <mrow> <mo stretchy="false">|</mo> <mi mathvariant="normal">Ω</mi> <mo stretchy="false">|</mo> </mrow> </mfrac> <msub> <mo>∫</mo> <mi mathvariant="normal">Ω</mi> </msub> <msub> <mi>u</mi> <mn>0</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <mspace width="0.166667em" /> <mtext>d</mtext> <mi>x</mi> </mrow> </math></EquationSource> </InlineEquation> is positive and <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(f\in C^2([0,\infty ))\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo>∈</mo> <msup> <mi>C</mi> <mn>2</mn> </msup> <mrow> <mo stretchy="false">(</mo> <mrow> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mi>∞</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> with <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(f(0)=0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo stretchy="false">(</mo> <mn>0</mn> <mo stretchy="false">)</mo> <mo>=</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> equals some nonlinear function of the particle density. This paper proves that:<UnorderedList Mark="Bullet"> <ItemContent> <p>Let <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(f(u)\ge ku^p\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> <mo>≥</mo> <mi>k</mi> <msup> <mi>u</mi> <mi>p</mi> </msup> </mrow> </math></EquationSource> </InlineEquation> for all <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(u\ge 1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>u</mi> <mo>≥</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> with some <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(k &gt; 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>k</mi> <mo>&gt;</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(p&gt;0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>&gt;</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>. If <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(\Omega \)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">Ω</mi> </math></EquationSource> </InlineEquation> is a ball and <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(p&gt;(1-\frac{1}{n})\beta +\frac{2}{n}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>&gt;</mo> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo>-</mo> <mfrac> <mn>1</mn> <mi>n</mi> </mfrac> <mo stretchy="false">)</mo> </mrow> <mi>β</mi> <mo>+</mo> <mfrac> <mn>2</mn> <mi>n</mi> </mfrac> </mrow> </math></EquationSource> </InlineEquation>, there exist some radially symmetric initial data such that the corresponding solution blows up in finite time.</p> </ItemContent> <ItemContent> <p>Let <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(f(u)\le K(u+1)^p\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> <mo>≤</mo> <mi>K</mi> <msup> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo>+</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> <mi>p</mi> </msup> </mrow> </math></EquationSource> </InlineEquation> for all <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(u\ge 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>u</mi> <mo>≥</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> with some <InlineEquation ID="IEq14"> <EquationSource Format="TEX">\(K &gt; 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>K</mi> <mo>&gt;</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq15"> <EquationSource Format="TEX">\(p&gt;0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>&gt;</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>. If <InlineEquation ID="IEq16"> <EquationSource Format="TEX">\(0&lt;p&lt;(1-\frac{1}{n})\beta +\frac{2}{n}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <mo>&lt;</mo> <mi>p</mi> <mo>&lt;</mo> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo>-</mo> <mfrac> <mn>1</mn> <mi>n</mi> </mfrac> <mo stretchy="false">)</mo> </mrow> <mi>β</mi> <mo>+</mo> <mfrac> <mn>2</mn> <mi>n</mi> </mfrac> </mrow> </math></EquationSource> </InlineEquation>, all solutions are global and uniformly bounded.</p> </ItemContent> </UnorderedList></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

A critical blow-up exponent for a Keller–Segel system with nonlinear sensitivity and flux limitation

  • Jianlu Yan

摘要

In this work, we investigate the following Keller–Segel system with nonlinear sensitivity and flux limitation \(\begin{aligned} {\left\{ \begin{array}{ll} \begin{array}{lll} u_t=\Delta u-\nabla \cdot \left( \frac{f(u)\nabla v}{(1+|\nabla v|^2)^\frac{\beta }{2}} \right) ,&x \in \Omega , t>0, 0=\Delta v-\mu +u,&x \in \Omega , t>0, \end{array} \end{array}\right. } \end{aligned}\) u t = Δ u - · f ( u ) v ( 1 + | v | 2 ) β 2 , x Ω , t > 0 , 0 = Δ v - μ + u , x Ω , t > 0 , under homogeneous Neumann-type boundary conditions in a bounded domain \(\Omega \subset \mathbb {R}^n (n \ge 2\) Ω R n ( n 2 ), where \(\beta \in (0, 1]\) β ( 0 , 1 ] , \( \mu :=\frac{1}{|\Omega |} \int _{\Omega } u_0(x) \,\textrm{d}x \) μ : = 1 | Ω | Ω u 0 ( x ) d x is positive and \(f\in C^2([0,\infty ))\) f C 2 ( [ 0 , ) ) with \(f(0)=0\) f ( 0 ) = 0 equals some nonlinear function of the particle density. This paper proves that:

Let \(f(u)\ge ku^p\) f ( u ) k u p for all \(u\ge 1\) u 1 with some \(k > 0\) k > 0 and \(p>0\) p > 0 . If \(\Omega \) Ω is a ball and \(p>(1-\frac{1}{n})\beta +\frac{2}{n}\) p > ( 1 - 1 n ) β + 2 n , there exist some radially symmetric initial data such that the corresponding solution blows up in finite time.

Let \(f(u)\le K(u+1)^p\) f ( u ) K ( u + 1 ) p for all \(u\ge 0\) u 0 with some \(K > 0\) K > 0 and \(p>0\) p > 0 . If \(0<p<(1-\frac{1}{n})\beta +\frac{2}{n}\) 0 < p < ( 1 - 1 n ) β + 2 n , all solutions are global and uniformly bounded.