QCD on a small circle

TL;DR

This paper investigates the spectrum of hadronic states in small-circle QCD-like theories, revealing a Hagedorn density of states and non-perturbative energy scales, advancing understanding of confinement and spectrum in controlled settings.

Contribution

It provides a detailed analysis of the hadronic spectrum, including glueballs, mesons, and baryons, in small-circle QCD-like theories, highlighting exponential growth and non-perturbative scales.

Findings

Exponential Hagedorn density of states observed.

Non-perturbative energy scales are iterated exponentials of inverse coupling.

Spectrum includes glueball, meson, and baryon resonances.

Abstract

QCD-like theories can be engineered to remain in a confined phase when compactified on an arbitrarily small circle, where their features may be studied quantitatively in a controlled fashion. Previous work has elucidated the generation of a non-perturbative mass gap and the spontaneous breaking of chiral symmetry in this regime. Here, we study the rich spectrum of hadronic states, including glueball, meson, and baryon resonances. We find an exponentially growing Hagedorn density of states, as well as the emergence of non-perturbative energy scales given by iterated exponentials of the inverse Yang-Mills coupling $g^2$.