Dynamics of the collision of two nearly equal solitary waves for the Zakharov-Kuznetsov equation

TL;DR

This paper investigates the collision dynamics of two nearly equal solitary waves in the Zakharov-Kuznetsov equation across 2D and 3D, demonstrating their stability and describing their evolution over time.

Contribution

It extends the analysis of solitary wave collisions to higher dimensions for the Zakharov-Kuznetsov equation, introducing new methods for constructing approximate solutions and controlling their stability.

Findings

Solutions behave as sum of two modulated solitary waves over time

The collision solution remains stable for large times

Constructed an intrinsic approximate solution despite non-explicit solitary waves

Abstract

We study the dynamics of the collision of two solitary waves for the Zakharov-Kuznetsov equation in dimension $2$ and $3$. We describe the evolution of the solution behaving as a sum of $2$-solitary waves of nearly equal speeds at time $t=-\infty$ up to time $t=+\infty$. We show that this solution behaves as the sum of two modulated solitary waves and an error term which is small in $H^1$ for all time $t \in \mathbb R$. Finally, we also prove the stability of this solution for large times around the collision. The proofs are a non-trivial extension of the ones of Martel and Merle for the quartic generalized Korteweg-de Vries equation to higher dimensions. First, despite the non-explicit nature of the solitary wave, we construct an approximate solution in an intrinsic way by canceling the error to the equation only in the natural directions of scaling and translation. Then, to control the difference between a solution and the approximate solution, we use a modified energy functional and a refined modulation estimate in the transverse variable. Moreover, we rely on the hamiltonian structure of the ODE governing the distance between the waves, which cannot be approximated by explicit solutions, to close the bootstrap estimates on the parameters. We hope that the techniques introduced here are robust and will prove useful in studying the collision phenomena for other focusing non-linear dispersive equations with non-explicit solitary waves.