# Kinks and Particles in Non-integrable Quantum Field Theories

## TL;DR

This paper derives the semi-classical spectrum of neutral particles in non-integrable quantum field theories with kink excitations, revealing limitations on stable particles per vacuum and the nature of other excitations as resonances.

## Contribution

It provides an elementary derivation of the semi-classical spectrum and clarifies the stability constraints of particles in non-integrable models.

## Key findings

- Each vacuum supports at most two stable particles.
- All other neutral excitations are resonances that decay.
- The derivation applies to theories with kink excitations.

## Abstract

In this talk we discuss an elementary derivation of the semi-classical spectrum of neutral particles in two field theories with kink excitations. We also show that, in the non-integrable cases, each vacuum state cannot generically support more than two stable particles, since all other neutral exitations are resonances, which will eventually decay.