Pohlmeyer reduction of Newton-Cartan strings

Abstract

We develop a Pohlmeyer-type reduction for classical non-relativistic strings on string Newton-Cartan backgrounds. For strings on a two-sphere, we identify the invariant reduced field, show that its dynamics is integrable, and construct a Lax representation. We relate this intrinsic formulation to the non-relativistic expansion of relativistic strings and obtain a dictionary between non-relativistic string solutions and their reduced counterparts. The construction explicitly determines which relativistic solitonic configurations survive the non-relativistic limit and which decouple. Moreover, it provides a framework for applying integrability methods to Newton-Cartan string dynamics.