Conservation Laws and Geometry of Perturbed Coset Models

TL;DR

This paper develops a Lagrangian framework for a perturbed coset model, revealing its integrability, conservation laws, and geometric interpretation, with applications to related quantum field theories.

Contribution

It introduces a Lagrangian description of the perturbed $SU(2)/U(1)$ coset model, deriving conservation laws and connecting to geometric and algebraic structures.

Findings

Classical equivalence to the $O(4)$ sigma model for negative coupling

Relativistic vortex motion description for positive coupling

Construction of higher spin currents using $W_{}$ generators

Abstract

We present a Lagrangian description of the $SU(2)/U(1)$ coset model perturbed by its first thermal operator. This is the simplest perturbation that changes sign under Krammers--Wannier duality. The resulting theory, which is a 2--component generalization of the sine--Gordon model, is then taken in Minkowski space. For negative values of the coupling constant $g$, it is classically equivalent to the $O(4)$ non--linear $\s$--model reduced in a certain frame. For $g > 0$, it describes the relativistic motion of vortices in a constant external field. Viewing the classical equations of motion as a zero curvature condition, we obtain recursive relations for the infinitely many conservation laws by the abelianization method of gauge connections. The higher spin currents are constructed entirely using an off--critical generalization of the $W_{\infty}$ generators. We give a geometric interpretation to the corresponding charges in terms of embeddings. Applications to the chirally invariant $U(2)$ Gross--Neveu model are also discussed.