Computation of the response functions of spiral waves in active media

TL;DR

This paper introduces a new, general computational method for calculating the response functions of spiral waves in reaction-diffusion systems, with applications demonstrated on the FitzHugh-Nagumo model, showing localized sensitivity at the spiral core.

Contribution

The paper presents a regular, generic approach for computing spiral wave response functions, improving accuracy and convergence analysis in reaction-diffusion models.

Findings

RFs are localized at the spiral core

Method converges with respect to discretization and medium size

Applied successfully to FitzHugh-Nagumo system

Abstract

Rotating spiral waves are a form of self-organization observed in spatially extended systems of physical, chemical, and biological nature. A small perturbation causes gradual change in spatial location of spiral's rotation center and frequency, i.e. drift. The response functions (RFs) of a spiral wave are the eigenfunctions of the adjoint linearized operator corresponding to the critical eigenvalues $\lambda = 0, \pm i\omega$. The RFs describe the spiral's sensitivity to small perturbations in the way that a spiral is insensitive to small perturbations where its RFs are close to zero. The velocity of a spiral's drift is proportional to the convolution of RFs with the perturbation. Here we develop a regular and generic method of computing the RFs of stationary rotating spirals in reaction-diffusion equations. We demonstrate the method on the FitzHugh-Nagumo system and also show convergence of the method with respect to the computational parameters, i.e. discretization steps and size of the medium. The obtained RFs are localized at the spiral's core.