Some Exact Results in QCD-like Theories

TL;DR

This paper uses a supersymmetric approximation with anomaly-mediated breaking to analyze QCD-like theories, revealing conditions for chiral symmetry breaking and infrared fixed points, and suggesting universality between different regimes.

Contribution

It introduces a controlled approximation method for QCD-like theories using supersymmetry and anomaly mediation, providing exact results in certain limits.

Findings

Chiral symmetry is broken for Nf ≤ 1.5 Nc.

Non-trivial infrared fixed points occur for larger Nf.

Qualitative agreement with QCD expectations suggests universality.

Abstract

I propose a controlled approximation to QCD-like theories with massless quarks by employing supersymmetric QCD perturbed by anomaly-mediated supersymmetry breaking. They have identical massless particle contents. Thanks to the ultraviolet-insensitivity of anomaly mediation, dynamics can be worked out exactly when $m \ll \Lambda$, where $m$ is the size of supersymmetry breaking and $\Lambda$ the dynamical scale of the gauge theory. I demonstrate that chiral symmetry is dynamically broken for $N_{f} \leq \frac{3}{2} N_{c}$ while the theories lead to non-trivial infrared fixed points for larger number of flavors. While there may be a phase transition as $m$ is increased beyond $\Lambda$, qualitative agreements with expectations in QCD are encouraging and suggest that two limits $m \ll \Lambda$ and $m \gg \Lambda$ may be in the same universality class.