Particle Content of the Nonlinear Sigma Model with Theta-Term: a Lattice Model Investigation

TL;DR

This paper investigates the low-energy spectrum of the O(3) Nonlinear Sigma Model with a theta-term using lattice models, revealing stable singlet bound states at strong coupling and proposing a new RG flow diagram.

Contribution

It introduces new lattice-based insights into the particle content of the nonlinear sigma model with a theta-term, especially regarding bound states and RG flows.

Findings

Stable singlet bound states exist at certain theta values.

A new renormalization group flow diagram is proposed.

Results are based on dimerized quantum spin chains with frustration.

Abstract

Using new as well as known results on dimerized quantum spin chains with frustration, we are able to infer some properties on the low-energy spectrum of the O(3) Nonlinear Sigma Model with a topological theta-term. In particular, for sufficiently strong coupling, we find a range of values of theta where a singlet bound state is stable under the triplet continuum. On the basis of these results, we propose a new renormalization group flow diagram for the Nonlinear Sigma Model with theta-term.