Shock-fronted travelling waves in a reaction–diffusion model with nonlinear forward–backward–forward diffusion

Yifei Li, Peter van Heijster*, Matthew J. Simpson, Martin Wechselberger

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Reaction–diffusion equations (RDEs) are often derived as continuum limits of lattice-based discrete models. Recently, a discrete model which allows the rates of movement, proliferation and death to depend upon whether the agents are isolated has been proposed, and this approach gives various RDEs where the diffusion term is convex and can become negative (Johnston et al., 2017), i.e. forward–backward–forward diffusion. Numerical simulations suggest these RDEs support shock-fronted travelling waves when the reaction term includes an Allee effect. In this work we formalise these preliminary numerical observations by analysing the shock-fronted travelling waves through embedding the RDE into a larger class of higher order partial differential equations (PDEs). Subsequently, we use geometric singular perturbation theory to study this larger class of equations and prove the existence of these shock-fronted travelling waves. Most notable, we show that different embeddings yield shock-fronted travelling waves with different properties.

Original languageEnglish
Article number132916
JournalPhysica D: Nonlinear Phenomena
Publication statusE-pub ahead of print - 17 Apr 2021


  • Lattice-based discrete model
  • Perturbation theory
  • Phase plane
  • Regularisation


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