<p>We study the existence of traveling waves for nonlocal KPP–Fisher equations with diffusive delay <Equation ID="Equ50"> <MediaObject> <ImageObject Color="BlackWhite" FileRef="28_2025_1064_Article_Equ50.gif" Format="GIF" Height="44" Rendition="HTML" Resolution="72" Type="Linedraw" Width="492" /> </MediaObject> <EquationSource Format="TEX">\(\begin{aligned} \frac{\partial u(x,t)}{\partial t}=\frac{\partial ^2u (x,t-\tau _1)}{\partial x^2}+u(x,t)\left( 1-\int \nolimits _{-\infty }^{\infty }\textrm{d}\mu (y)u(x-y,t-\tau _2)\right) , \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mrow> <mfrac> <mrow> <mi>∂</mi> <mi>u</mi> <mo stretchy="false">(</mo> <mi>x</mi> <mo>,</mo> <mi>t</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mi>∂</mi> <mi>t</mi> </mrow> </mfrac> <mo>=</mo> <mfrac> <mrow> <msup> <mi>∂</mi> <mn>2</mn> </msup> <mi>u</mi> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo>,</mo> <mi>t</mi> <mo>-</mo> <msub> <mi>τ</mi> <mn>1</mn> </msub> <mo stretchy="false">)</mo> </mrow> </mrow> <mrow> <mi>∂</mi> <msup> <mi>x</mi> <mn>2</mn> </msup> </mrow> </mfrac> <mo>+</mo> <mi>u</mi> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo>,</mo> <mi>t</mi> <mo stretchy="false">)</mo> </mrow> <mfenced close=")" open="("> <mn>1</mn> <mo>-</mo> <msubsup> <mo>∫</mo> <mrow> <mo>-</mo> <mi>∞</mi> </mrow> <mi>∞</mi> </msubsup> <mtext>d</mtext> <mi>μ</mi> <mrow> <mo stretchy="false">(</mo> <mi>y</mi> <mo stretchy="false">)</mo> </mrow> <mi>u</mi> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo>-</mo> <mi>y</mi> <mo>,</mo> <mi>t</mi> <mo>-</mo> <msub> <mi>τ</mi> <mn>2</mn> </msub> <mo stretchy="false">)</mo> </mrow> </mfenced> <mo>,</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>where <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="28_2025_1064_Article_IEq1.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mu \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>μ</mi> </math></EquationSource> </InlineEquation> is a nondecreasing function with bounded variation. The existence of traveling waves is proved using the method of monotone iteration developed recently for general reaction–diffusion equations with delays in both reaction and diffusion terms. We extend this iteration method to start with very rough upper and lower solutions that we call supper and subsolutions. We show that for small delays <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="28_2025_1064_Article_IEq2.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\tau _1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>τ</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="28_2025_1064_Article_IEq3.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\tau _2\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>τ</mi> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation> traveling waves connecting 0 and 1 exist. The obtained results appear to be new.</p>

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Traveling waves for nonlocal Fisher–KPP equations with diffusive delay

  • Nguyen Truong Thanh,
  • William Barker,
  • Nguyen Van Minh

摘要

We study the existence of traveling waves for nonlocal KPP–Fisher equations with diffusive delay \(\begin{aligned} \frac{\partial u(x,t)}{\partial t}=\frac{\partial ^2u (x,t-\tau _1)}{\partial x^2}+u(x,t)\left( 1-\int \nolimits _{-\infty }^{\infty }\textrm{d}\mu (y)u(x-y,t-\tau _2)\right) , \end{aligned}\) u ( x , t ) t = 2 u ( x , t - τ 1 ) x 2 + u ( x , t ) 1 - - d μ ( y ) u ( x - y , t - τ 2 ) , where \(\mu \) μ is a nondecreasing function with bounded variation. The existence of traveling waves is proved using the method of monotone iteration developed recently for general reaction–diffusion equations with delays in both reaction and diffusion terms. We extend this iteration method to start with very rough upper and lower solutions that we call supper and subsolutions. We show that for small delays \(\tau _1\) τ 1 and \(\tau _2\) τ 2 traveling waves connecting 0 and 1 exist. The obtained results appear to be new.