Integrable Quantum Field Theories with Unstable Particles

TL;DR

This paper reviews a new class of integrable quantum field theories with resonance poles, unstable particles, and multiple mass scales, supported by TBA and form factor calculations, linking them to Homogeneous sine-Gordon models.

Contribution

It introduces a new family of factorised S-matrix theories with resonance poles and unstable particles, connecting them to Homogeneous sine-Gordon theories for simply laced Lie groups.

Findings

Resonance poles correspond to unstable particles.

Theories involve several independent mass scales.

TBA and form factor calculations support the conjecture.

Abstract

The structure of a new family of factorised $S$-matrix theories with resonance poles is reviewed. They are conjectured to correspond to the Homogeneous sine-Gordon theories associated with simply laced compact Lie groups. Two of their more remarkable properties are, first, that some of the resonance poles can be traced to the presence of unstable particles in the spectrum, and, second, that they involve several independent mass scales. The conjectured relationship with the simply laced HSG theories has been checked by means of the Thermodynamic Bethe ansatz (TBA) and, more recently, through the explicit calculation of the Form Factors. The main results of the TBA analysis are summarized.