Harmonic Maps and Integrable Systems

Abstract

This article has two purposes. The first is to give an expository account of the integrable systems approach to harmonic maps from surfaces to Lie groups and symmetric spaces, focusing on spectral curves for harmonic 2-tori. The most unwieldy aspect of the spectral curve description is the periodicity conditions and the second aim is to present four different forms for these periodicity conditions and explain their equivalence.