$G$-Strands on symmetric spaces

Abstract

We study the $G$-strand equations that are extensions of the classical chiral model of particle physics in the particular setting of broken symmetries described by symmetric spaces. These equations are simple field theory models whose configuration space is a Lie group, or in this case a symmetric space. In this class of systems, we derive several models that are completely integrable on finite dimensional Lie group $G$ and we treat in more details examples with symmetric space $SU(2)/S^1$ and $SO(4)/SO(3)$. The later model simplifies to an apparently new integrable $9$ dimensional system. We also study the $G$-strands on the infinite dimensional group of diffeomorphisms, which gives, together with the Sobolev norm, systems of $1+2$ Camassa-Holm equations. The solutions of these equations on the complementary space related to the Witt algebra decomposition are the odd function solutions.