Traveling pulses with oscillatory tails, figure-eight-like stack of isolas, and dynamics in heterogeneous media

Abstract

The interplay between 1D traveling pulses with oscillatory tails (TPO) and heterogeneities of bump type is studied for a generalized three-component FitzHugh-Nagumo equation. First, we present that stationary pulses with oscillatory tails (SPO) form a ``snaky'' structure in homogeneous spaces, after which TPO branches form a ``figure-eight-like stack of isolas'' located adjacent to the snaky structure of SPO. Herein, we adopted input resources as a bifurcation parameter. A drift bifurcation from SPO to TPO was observed by introducing another parameter at which these two solution sheets merged. In contrast to the monotone tail case, a nonlocal interaction appeared in the heterogeneous problem between the TPO and heterogeneity, which created infinitely many saddle solutions and finitely many stable stationary solutions distributed across the entire line. TPO displayed a variety of dynamics including pinning and depinning processes along with penetration (PEN) and rebound (REB). The stable/unstable manifolds of these saddles interacted with the TPO in a complex manner, which created a subtle dependence on the initial condition, and a difficulty to predict the behavior after collision. A systematic global exploration of solution branches induced by heterogeneities enabled us to find all the asymptotic states after collision to predict the solution results without solving the PDEs. The reduction method of finite-dimensional ODE system allowed us to clarify the detailed mechanism of the transitions from PEN to pinning and pinning to REB based on a dynamical system perspective. Consequently, the basin boundary between two distinct outputs against the heterogeneities yielded an infinitely many successive reconnection of heteroclinic orbits among those saddles, because the strength of heterogeneity increased and caused the aforementioned subtle dependence of initial condition.