Abstract:
We study a Rock-Paper-Scissors model that describes the spatiotemporal evolution of three competing populations in ecology, or strategies in evolutionary game theory. The dynamics of the model is determined by a set of partial differential equations (PDEs) in a reaction-diffusion form; it exhibits travelling waves (TWs) in one spatial dimension and spiral waves in two spatial dimensions. In this paper, we focus on the stability of the TWs in a one-dimensional version of this model. A characteristic feature of the model is the presence of a robust heteroclinic cycle that involves three saddle equilibria. This heteroclinic cycle gives rise to a family of periodic TWs. The existence of heteroclinic cycles and associated periodic TWs can be established via the transformation of the PDE model into a system of ordinary differential equations (ODEs) under the assumption that the wave speed is constant. Determining the stability of periodic TWs is more challenging and requires analysis of the essential spectrum of the linear operator of the periodic TWs. We compute this spectrum and the curve of instability with the continuation scheme developed in [Rademacher, Sandstede, and Scheel, Physica D, Vol. 229, 2007]. We also build on this scheme and develop a method for computing what we call belts of instability, which are indicators of the growth rate of unstable TWs. We finally show that our results from the stability analysis are verified by direct simulation of the PDE model and how the computed growth rates accurately quantify the instabilities of the travelling waves.
