Some Exact Results in QCD-like Theories
Hitoshi Murayama
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 $m\ensuremath{\ll}\mathrm{\ensuremath{\Lambda}}$, where $m$ is the size of supersymmetry breaking and $\mathrm{\ensuremath{\Lambda}}$ the dynamical scale of the gauge theory. I demonstrate that chiral symmetry is dynamically broken for ${N}_{f}\ensuremath{\le}\frac{3}{2}{N}_{c}$ while the theories lead to nontrivial infrared fixed points for larger number of flavors. While there may be a phase transition as $m$ is increased beyond $\mathrm{\ensuremath{\Lambda}}$, qualitative agreements with expectations in QCD are encouraging and suggest that two limits $m\ensuremath{\ll}\mathrm{\ensuremath{\Lambda}}$ and $m\ensuremath{\gg}\mathrm{\ensuremath{\Lambda}}$ may be in the same universality class.