<p>In this article we present the existence of infinitely many non-radial positive or sign-changing solutions for the following FitzHugh–Nagumosystem: <Equation ID="Equ66"> <MediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_Equ66.gif" Format="GIF" Height="65" Rendition="HTML" Resolution="72" Type="Linedraw" Width="360" /> </MediaObject> <EquationSource Format="TEX">\(\begin{aligned} \left\{ \begin{array}{ll} \Delta u-a(|x|)u+g(u)-\delta v=0, \quad &amp; x\in \mathbb {R}^N,\\ \Delta v+u=0, &amp; x\in \mathbb {R}^N,\\ u(x), ~v(x)\rightarrow 0, &amp; \text{ as }~ |x|\rightarrow +\infty ,\\ \end{array}\right. \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mfenced open="{"> <mrow> <mtable> <mtr> <mtd columnalign="left"> <mrow> <mi mathvariant="normal">Δ</mi> <mi>u</mi> <mo>-</mo> <mi>a</mi> <mo stretchy="false">(</mo> <mo stretchy="false">|</mo> <mi>x</mi> <mo stretchy="false">|</mo> <mo stretchy="false">)</mo> <mi>u</mi> <mo>+</mo> <mi>g</mi> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> <mo>-</mo> <mi>δ</mi> <mi>v</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mspace width="1em" /> </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> </mrow> </mtd> </mtr> <mtr> <mtd columnalign="left"> <mrow> <mrow /> <mi mathvariant="normal">Δ</mi> <mi>v</mi> <mo>+</mo> <mi>u</mi> <mo>=</mo> <mn>0</mn> <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> </mrow> </mtd> </mtr> <mtr> <mtd columnalign="left"> <mrow> <mrow /> <mi>u</mi> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> <mo>,</mo> <mspace width="3.33333pt" /> <mi>v</mi> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> <mo stretchy="false">→</mo> <mn>0</mn> <mo>,</mo> </mrow> </mtd> <mtd columnalign="left"> <mrow> <mspace width="0.333333em" /> <mtext>as</mtext> <mspace width="0.333333em" /> <mspace width="3.33333pt" /> <mo stretchy="false">|</mo> <mi>x</mi> <mo stretchy="false">|</mo> <mo stretchy="false">→</mo> <mo>+</mo> <mi>∞</mi> <mo>,</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </mfenced> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>where <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq3.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">\(N\ge 5\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>N</mi> <mo>≥</mo> <mn>5</mn> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq4.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="40" /> </InlineMediaObject> <EquationSource Format="TEX">\(\delta &gt;0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>δ</mi> <mo>&gt;</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq5.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="163" /> </InlineMediaObject> <EquationSource Format="TEX">\(g(u)=(a_0+1)u^2-u^3\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>g</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mrow> <mo stretchy="false">(</mo> <msub> <mi>a</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> <msup> <mi>u</mi> <mn>2</mn> </msup> <mo>-</mo> <msup> <mi>u</mi> <mn>3</mn> </msup> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq6.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="77" /> </InlineMediaObject> <EquationSource Format="TEX">\(0&lt;a_0&lt;\frac{1}{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <mo>&lt;</mo> <msub> <mi>a</mi> <mn>0</mn> </msub> <mo>&lt;</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq7.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="99" /> </InlineMediaObject> <EquationSource Format="TEX">\(a(|x|)\in (0,\frac{1}{2})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>a</mi> <mrow> <mo stretchy="false">(</mo> <mo stretchy="false">|</mo> <mi>x</mi> <mo stretchy="false">|</mo> <mo stretchy="false">)</mo> </mrow> <mo>∈</mo> <mrow> <mo stretchy="false">(</mo> <mn>0</mn> <mo>,</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> satisfies some decay conditions at the infinity. More precisely, for any positive integer <i>k</i> large, there is a <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq8.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="47" /> </InlineMediaObject> <EquationSource Format="TEX">\(\delta _k&gt;0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>δ</mi> <mi>k</mi> </msub> <mo>&gt;</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> such that for <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq9.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="79" /> </InlineMediaObject> <EquationSource Format="TEX">\(0&lt;\delta &lt;\delta _k\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <mo>&lt;</mo> <mi>δ</mi> <mo>&lt;</mo> <msub> <mi>δ</mi> <mi>k</mi> </msub> </mrow> </math></EquationSource> </InlineEquation>, there exists positive solutions with 2<i>k</i> peaks, which are respectively concentrated at the vertices of a regular <i>k</i>-polygon on two circles in 3-dimensional space with the radium <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq10.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="73" /> </InlineMediaObject> <EquationSource Format="TEX">\(r\sim k \ln k\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>r</mi> <mo>∼</mo> <mi>k</mi> <mo>ln</mo> <mi>k</mi> </mrow> </math></EquationSource> </InlineEquation> and the height <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq11.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="44" /> </InlineMediaObject> <EquationSource Format="TEX">\(h\sim \frac{1}{k}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>h</mi> <mo>∼</mo> <mfrac> <mn>1</mn> <mi>k</mi> </mfrac> </mrow> </math></EquationSource> </InlineEquation>. In addition, the sign-changing solutions with 2<i>k</i> peaks are evenly distributed on the equatorial <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq12.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="205" /> </InlineMediaObject> <EquationSource Format="TEX">\(\textrm{T}=\{x\in \mathbb {R}^2:x_1^2+x_2^2=r^2\}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mtext>T</mtext> <mo>=</mo> <mo stretchy="false">{</mo> <mi>x</mi> <mo>∈</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mn>2</mn> </msup> <mo>:</mo> <msubsup> <mi>x</mi> <mn>1</mn> <mn>2</mn> </msubsup> <mo>+</mo> <msubsup> <mi>x</mi> <mn>2</mn> <mn>2</mn> </msubsup> <mo>=</mo> <msup> <mi>r</mi> <mn>2</mn> </msup> <mo stretchy="false">}</mo> </mrow> </math></EquationSource> </InlineEquation> in the <InlineEquation ID="IEq13"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq13.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="53" /> </InlineMediaObject> <EquationSource Format="TEX">\((x_1, x_2)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <msub> <mi>x</mi> <mn>1</mn> </msub> <mo>,</mo> <msub> <mi>x</mi> <mn>2</mn> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>-plane. As a by-product, we give the similar results of Schödinger-Poisson in <InlineEquation ID="IEq14"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq1.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <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="IEq15"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10231_2025_1548_Article_IEq15.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">\(N\ge 3\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>N</mi> <mo>≥</mo> <mn>3</mn> </mrow> </math></EquationSource> </InlineEquation>.</p>

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Non-radial positive and sign-changing solutions for the FitzHugh–Nagumo system in \(\mathbb {R}^N\)

  • Weihong Xie,
  • Mingzhu Yu

摘要

In this article we present the existence of infinitely many non-radial positive or sign-changing solutions for the following FitzHugh–Nagumosystem: \(\begin{aligned} \left\{ \begin{array}{ll} \Delta u-a(|x|)u+g(u)-\delta v=0, \quad & x\in \mathbb {R}^N,\\ \Delta v+u=0, & x\in \mathbb {R}^N,\\ u(x), ~v(x)\rightarrow 0, & \text{ as }~ |x|\rightarrow +\infty ,\\ \end{array}\right. \end{aligned}\) Δ u - a ( | x | ) u + g ( u ) - δ v = 0 , x R N , Δ v + u = 0 , x R N , u ( x ) , v ( x ) 0 , as | x | + , where \(N\ge 5\) N 5 , \(\delta >0\) δ > 0 , \(g(u)=(a_0+1)u^2-u^3\) g ( u ) = ( a 0 + 1 ) u 2 - u 3 , \(0<a_0<\frac{1}{2}\) 0 < a 0 < 1 2 and \(a(|x|)\in (0,\frac{1}{2})\) a ( | x | ) ( 0 , 1 2 ) satisfies some decay conditions at the infinity. More precisely, for any positive integer k large, there is a \(\delta _k>0\) δ k > 0 such that for \(0<\delta <\delta _k\) 0 < δ < δ k , there exists positive solutions with 2k peaks, which are respectively concentrated at the vertices of a regular k-polygon on two circles in 3-dimensional space with the radium \(r\sim k \ln k\) r k ln k and the height \(h\sim \frac{1}{k}\) h 1 k . In addition, the sign-changing solutions with 2k peaks are evenly distributed on the equatorial \(\textrm{T}=\{x\in \mathbb {R}^2:x_1^2+x_2^2=r^2\}\) T = { x R 2 : x 1 2 + x 2 2 = r 2 } in the \((x_1, x_2)\) ( x 1 , x 2 ) -plane. As a by-product, we give the similar results of Schödinger-Poisson in \(\mathbb {R}^N\) R N for \(N\ge 3\) N 3 .