Long-time asymptotics in the modified Landau-Lifshitz equation with nonzero boundary conditions

Abstract

In this work, we consider the long-time asymptotics of the modified Landau-Lifshitz equation with nonzero boundary conditions (NZBCs) at infinity. The critical technique is the deformations of the corresponding matrix Riemann-Hilbert problem via the nonlinear steepest descent method, as well as we employ the $g$-function mechanism to eliminate the exponential growths of the jump matrices. The results indicate that the solution of the modified Landau-Lifshitz equation with nonzero boundary conditions admits two different asymptotic behavior corresponding to two types of regions in the $xt$-plane. They are called the plane wave region with $x<(\beta-4\sqrt{2}q_{0})t, x>(\beta+4\sqrt{2}q_{0})t$, and the modulated elliptic wave region with $(\beta-4\sqrt{2}q_{0})t<x< (\beta+4\sqrt{2}q_{0})t$, respectively.