<p>This paper deals with the existence of positive radial solutions of the elliptic equation with nonlinear gradient term <Equation ID="Equ68"> <EquationSource Format="TEX">\(\begin{aligned} \left\{ \begin{array}{ll} -\triangle u = f(|x|,\;u,\;|\nabla u|),\qquad x\in \Omega ,\\ u|_{\partial \Omega }=0\,, \end{array}\right. \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mfenced open="{"> <mrow> <mtable> <mtr> <mtd columnalign="left"> <mrow> <mo>-</mo> <mi>▵</mi> <mi>u</mi> <mo>=</mo> <mi>f</mi> <mo stretchy="false">(</mo> <mo stretchy="false">|</mo> <mi>x</mi> <mo stretchy="false">|</mo> <mo>,</mo> <mspace width="0.277778em" /> <mi>u</mi> <mo>,</mo> <mspace width="0.277778em" /> <mo stretchy="false">|</mo> <mi mathvariant="normal">∇</mi> <mi>u</mi> <mo stretchy="false">|</mo> <mo stretchy="false">)</mo> <mo>,</mo> <mspace width="2em" /> <mi>x</mi> <mo>∈</mo> <mi mathvariant="normal">Ω</mi> <mo>,</mo> </mrow> </mtd> </mtr> <mtr> <mtd columnalign="left"> <mrow> <mmultiscripts> <mrow> <mrow /> <mi>u</mi> <mo stretchy="false">|</mo> </mrow> <mrow> <mi>∂</mi> <mi mathvariant="normal">Ω</mi> </mrow> <mrow /> </mmultiscripts> <mo>=</mo> <mn>0</mn> <mspace width="0.166667em" /> <mo>,</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </mfenced> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>where <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\Omega =\{x\in \mathbb {R}^N:\;r_1&lt;|x|&lt;r_2\}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Ω</mi> <mo>=</mo> <mo stretchy="false">{</mo> <mi>x</mi> <mo>∈</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>N</mi> </msup> <mo>:</mo> <mspace width="0.277778em" /> <msub> <mi>r</mi> <mn>1</mn> </msub> <mo>&lt;</mo> <mo stretchy="false">|</mo> <mi>x</mi> <mo stretchy="false">|</mo> <mo>&lt;</mo> <msub> <mi>r</mi> <mn>2</mn> </msub> <mo stretchy="false">}</mo> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(N\ge 3\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>N</mi> <mo>≥</mo> <mn>3</mn> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(f:[r_1,\,r_2]\times \mathbb {R}^+\times \mathbb {R}\rightarrow \mathbb {R}^+\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo>:</mo> <mrow> <mo stretchy="false">[</mo> <msub> <mi>r</mi> <mn>1</mn> </msub> <mo>,</mo> <mspace width="0.166667em" /> <msub> <mi>r</mi> <mn>2</mn> </msub> <mo stretchy="false">]</mo> </mrow> <mo>×</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mo>+</mo> </msup> <mo>×</mo> <mi mathvariant="double-struck">R</mi> <mo stretchy="false">→</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mo>+</mo> </msup> </mrow> </math></EquationSource> </InlineEquation> is continuous. Under some inequality conditions of <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(f(x,\,\xi ,\,\eta )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo stretchy="false">(</mo> <mi>x</mi> <mo>,</mo> <mspace width="0.166667em" /> <mi>ξ</mi> <mo>,</mo> <mspace width="0.166667em" /> <mi>η</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> when <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(|(\xi ,\,\eta )|\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">|</mo> <mo stretchy="false">(</mo> <mi>ξ</mi> <mo>,</mo> <mspace width="0.166667em" /> <mi>η</mi> <mo stretchy="false">)</mo> <mo stretchy="false">|</mo> </mrow> </math></EquationSource> </InlineEquation> is small and large, two existence results of positive radial solutions are obtained. These inequality conditions are related to the principal eigenvalue <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\lambda _1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>λ</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> of the corresponding linear eigenvalue problem, are optimal and allow that the nonlinearity <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(f(r,\,\xi ,\,\eta )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo stretchy="false">(</mo> <mi>r</mi> <mo>,</mo> <mspace width="0.166667em" /> <mi>ξ</mi> <mo>,</mo> <mspace width="0.166667em" /> <mi>η</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> is superlinear or sublinear growth on <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\xi \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>ξ</mi> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\eta \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>η</mi> </math></EquationSource> </InlineEquation> as <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(|(\xi ,\,\eta )|\rightarrow 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">|</mo> <mo stretchy="false">(</mo> <mi>ξ</mi> <mo>,</mo> <mspace width="0.166667em" /> <mi>η</mi> <mo stretchy="false">)</mo> <mo stretchy="false">|</mo> <mo stretchy="false">→</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> or <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(|(\xi ,\,\eta )|\rightarrow \infty \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">|</mo> <mo stretchy="false">(</mo> <mi>ξ</mi> <mo>,</mo> <mspace width="0.166667em" /> <mi>η</mi> <mo stretchy="false">)</mo> <mo stretchy="false">|</mo> <mo stretchy="false">→</mo> <mi>∞</mi> </mrow> </math></EquationSource> </InlineEquation>. The main results are proved by the fixed point index theory in cones.</p>

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Existence of positive radial solutions for the elliptic equations with nonlinear gradient terms

  • Yongxiang Li

摘要

This paper deals with the existence of positive radial solutions of the elliptic equation with nonlinear gradient term \(\begin{aligned} \left\{ \begin{array}{ll} -\triangle u = f(|x|,\;u,\;|\nabla u|),\qquad x\in \Omega ,\\ u|_{\partial \Omega }=0\,, \end{array}\right. \end{aligned}\) - u = f ( | x | , u , | u | ) , x Ω , u | Ω = 0 , where \(\Omega =\{x\in \mathbb {R}^N:\;r_1<|x|<r_2\}\) Ω = { x R N : r 1 < | x | < r 2 } , \(N\ge 3\) N 3 , \(f:[r_1,\,r_2]\times \mathbb {R}^+\times \mathbb {R}\rightarrow \mathbb {R}^+\) f : [ r 1 , r 2 ] × R + × R R + is continuous. Under some inequality conditions of \(f(x,\,\xi ,\,\eta )\) f ( x , ξ , η ) when \(|(\xi ,\,\eta )|\) | ( ξ , η ) | is small and large, two existence results of positive radial solutions are obtained. These inequality conditions are related to the principal eigenvalue \(\lambda _1\) λ 1 of the corresponding linear eigenvalue problem, are optimal and allow that the nonlinearity \(f(r,\,\xi ,\,\eta )\) f ( r , ξ , η ) is superlinear or sublinear growth on \(\xi \) ξ and \(\eta \) η as \(|(\xi ,\,\eta )|\rightarrow 0\) | ( ξ , η ) | 0 or \(|(\xi ,\,\eta )|\rightarrow \infty \) | ( ξ , η ) | . The main results are proved by the fixed point index theory in cones.