<p>We study travelling-wave solutions of the generalized Heimburg–Jackson equation for electromechanical pulses in lipid membranes. The model includes both fourth-order spatial dispersion (coefficient <i>m</i>) and mixed space–time dispersion (coefficient <i>h</i>), which combine into an effective dispersion parameter <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(m_{\textrm{eff}} = m + h c^{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>m</mi> <mtext>eff</mtext> </msub> <mo>=</mo> <mi>m</mi> <mo>+</mo> <mi>h</mi> <msup> <mi>c</mi> <mn>2</mn> </msup> </mrow> </math></EquationSource> </InlineEquation> that depends on wave speed <i>c</i>. The travelling-wave reduction yields a Duffing-type equation with linear coefficient <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\alpha \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>α</mi> </math></EquationSource> </InlineEquation>, quadratic nonlinearity <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\beta \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>β</mi> </math></EquationSource> </InlineEquation>, and cubic nonlinearity <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\gamma \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>γ</mi> </math></EquationSource> </InlineEquation>. We derive exact solutions including kink fronts, Jacobi elliptic waves of sn, cn, and dn type, solitary <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\({{\,\textrm{sech}\,}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mspace width="0.166667em" /> <mtext>sech</mtext> <mspace width="0.166667em" /> </mrow> </math></EquationSource> </InlineEquation> pulses, and rational blow-up profiles. Within this ansatz class, algebraic compatibility forces <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\beta = 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>β</mi> <mo>=</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> for the Jacobi elliptic and <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\({{\,\textrm{sech}\,}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mspace width="0.166667em" /> <mtext>sech</mtext> <mspace width="0.166667em" /> </mrow> </math></EquationSource> </InlineEquation> families, corresponding to purely cubic elastic response near the membrane phase transition; periodic orbits of the reduced Duffing equation for <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\beta \ne 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>β</mi> <mo>≠</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> lie outside this ansatz class and are constructed explicitly in Weierstrass elliptic form. Within the unshifted tanh-ansatz, kink waves require the equal-well condition <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(9\alpha \gamma = 2\beta ^{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>9</mn> <mi>α</mi> <mi>γ</mi> <mo>=</mo> <mn>2</mn> <msup> <mi>β</mi> <mn>2</mn> </msup> </mrow> </math></EquationSource> </InlineEquation>; the sign of <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(m_{\textrm{eff}}\gamma \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>m</mi> <mtext>eff</mtext> </msub> <mi>γ</mi> </mrow> </math></EquationSource> </InlineEquation> controls admissibility for the derived solution families. Using phase-plane analysis, we classify trajectories by parameter regions. We relate kink solutions to structural phase transitions in membranes, periodic waves to trains of electromechanical pulses, and solitary waves to nerve-like solitons. The results make explicit the ansatz scope under which these exact solutions are admissible, and unify the classical and improved Heimburg–Jackson formulations within a single dispersive framework.</p>

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Solutions of the generalized Heimburg–Jackson model for membrane pulses

  • Yousef AbuHour,
  • Mohammed Banikhalid,
  • Amirah Azmi

摘要

We study travelling-wave solutions of the generalized Heimburg–Jackson equation for electromechanical pulses in lipid membranes. The model includes both fourth-order spatial dispersion (coefficient m) and mixed space–time dispersion (coefficient h), which combine into an effective dispersion parameter \(m_{\textrm{eff}} = m + h c^{2}\) m eff = m + h c 2 that depends on wave speed c. The travelling-wave reduction yields a Duffing-type equation with linear coefficient \(\alpha \) α , quadratic nonlinearity \(\beta \) β , and cubic nonlinearity \(\gamma \) γ . We derive exact solutions including kink fronts, Jacobi elliptic waves of sn, cn, and dn type, solitary \({{\,\textrm{sech}\,}}\) sech pulses, and rational blow-up profiles. Within this ansatz class, algebraic compatibility forces \(\beta = 0\) β = 0 for the Jacobi elliptic and \({{\,\textrm{sech}\,}}\) sech families, corresponding to purely cubic elastic response near the membrane phase transition; periodic orbits of the reduced Duffing equation for \(\beta \ne 0\) β 0 lie outside this ansatz class and are constructed explicitly in Weierstrass elliptic form. Within the unshifted tanh-ansatz, kink waves require the equal-well condition \(9\alpha \gamma = 2\beta ^{2}\) 9 α γ = 2 β 2 ; the sign of \(m_{\textrm{eff}}\gamma \) m eff γ controls admissibility for the derived solution families. Using phase-plane analysis, we classify trajectories by parameter regions. We relate kink solutions to structural phase transitions in membranes, periodic waves to trains of electromechanical pulses, and solitary waves to nerve-like solitons. The results make explicit the ansatz scope under which these exact solutions are admissible, and unify the classical and improved Heimburg–Jackson formulations within a single dispersive framework.