$\mathbb{C}P^N$ sigma models via the $SU(2)$ coherent states approach

TL;DR

This paper unifies $SU(2)$ coherent states with $ ext{CP}^N$ sigma models on the Riemann sphere, providing explicit parametrizations of solutions and relating their properties to representation weights, including the Veronese immersion.

Contribution

It introduces an explicit parametrization of $ ext{CP}^N$ sigma model solutions using $SU(2)$ coherent states and Jacobi polynomials, linking analytical properties to representation weights.

Findings

Explicit solutions parametrized by Jacobi polynomials

Connection between solution types and representation weights

Veronese immersion as a special case

Abstract

In this paper we present results obtained from the unification of $SU(2)$ coherent states with $\mathbb{C}P^N$ sigma models defined on the Riemann sphere having finite actions. The set of coherent states generated by a vector belonging to a carrier space of an irreducible representation of the group gives rise to a map from the sphere into the set of rank-1 Hermitian projectors in that space. The map can be identified with a particular solution of the $\mathbb{C}P^N$ sigma model, where $N+1$ is equal to the dimension of the representation space. In particular a choice of the generating vector as the highest weight vector of the representation gives rise to the map known as a Veronese immersion. Using a description of the matrix elements of these representations in terms of Jacobi polynomials, we obtain an explicit parametrization of the solutions of the $\mathbb{C}P^N$ models, which has not been previously found. We relate the analytical properties of the solutions, which are known to belong to separate classes --- holomorphic, anti-holomorphic and various types of mixed ones --- to the weight corresponding to the chosen weight vector. Some examples of the described constructions are elaborated in detail in this paper.