Chiral asymmetry in propagation of soliton defects in crystalline backgrounds

TL;DR

This paper constructs new multi-soliton solutions for KdV and mKdV equations using Darboux-Crum transformations, revealing a chiral asymmetry in defect propagation over crystalline backgrounds and uncovering an underlying N=4 supersymmetric structure.

Contribution

It introduces a novel method to generate multi-soliton solutions exhibiting chiral asymmetry and links them to a supersymmetric algebraic framework.

Findings

KdV solitons propagate oppositely in crystalline backgrounds.

Multi-kink-antikink mKdV solitons have privileged directions depending on spectral gaps.

An N=4 supersymmetric structure underpins the solution construction.

Abstract

By applying Darboux-Crum transformations to a Lax pair formulation of the Korteweg-de Vries (KdV) equation, we construct new sets of multi-soliton solutions to it as well as to the modified Korteweg-de Vries (mKdV) equation. The obtained solutions exhibit a chiral asymmetry in propagation of different types of defects in crystalline backgrounds. We show that the KdV solitons of pulse and compression modulation types, which support bound states in semi-infinite and finite forbidden bands in the spectrum of the perturbed quantum one-gap Lame system, propagate in opposite directions with respect to the asymptotically periodic background. A similar but more complicated picture also appears for the multi-kink-antikink mKdV solitons that propagate with a privileged direction over topologically trivial or topologically nontrivial crystalline background in dependence on position of energy levels of the trapped bound states in the spectral gaps of the associated Dirac system. An exotic N=4 nonlinear supersymmetric structure incorporating Lax-Novikov integrals of a pair of perturbed Lame systems is shown to underlie the Miura-Darboux-Crum construction. It unifies the KdV and mKdV solutions, detects the defects and distinguishes their types, and identifies the types of crystalline backgrounds.