The higher grading structure of the WKI hierarchy and the two-component short pulse equation

TL;DR

This paper develops a higher grading algebraic framework for integrable hierarchies, introduces a two-component short pulse equation, and explores their connections to other models like sine-Gordon and Lund-Regge.

Contribution

It presents a novel algebraic construction of integrable hierarchies, derives a two-component short pulse equation, and links these models to well-known integrable systems.

Findings

Derived a two-component short pulse equation from the WKI hierarchy

Constructed loop-soliton solutions systematically

Established connections to sine-Gordon and Lund-Regge models

Abstract

A higher grading affine algebraic construction of integrable hierarchies, containing the Wadati-Konno-Ichikawa (WKI) hierarchy as a particular case, is proposed. We show that a two-component generalization of the Sch\" afer-Wayne short pulse equation arises quite naturally from the first negative flow of the WKI hierarchy. Some novel integrable nonautonomous models are also proposed. The conserved charges, both local and nonlocal, are obtained from the Riccati form of the spectral problem. The loop-soliton solutions of the WKI hierarchy are systematically constructed through gauge followed by reciprocal B\" acklund transformation, establishing the precise connection between the whole WKI and AKNS hierarchies. The connection between the short pulse equation with the sine-Gordon model is extended to a correspondence between the two-component short pulse equation and the Lund-Regge model.