Running coupling in the conformal window of large-Nf QCD

TL;DR

This paper investigates the behavior of QCD with many quark flavors, revealing a phase transition where the running coupling stabilizes and propagators follow power laws, influenced by the quark-gluon vertex structure.

Contribution

It provides a self-consistent Dyson-Schwinger equation analysis showing how the number of quark flavors affects the non-perturbative running coupling and propagator behavior in large-Nf QCD.

Findings

Identification of a phase transition at a critical number of flavors.

Development of a plateau in the non-perturbative running coupling.

Power law behavior of propagators in the conformal window.

Abstract

Quantum Chromodynamics with a relatively large number of fundamentally charged quark flavours in the chiral limit is considered. A self-consistent solution of the quark, gluon and ghost propagator Dyson-Schwinger equations in Landau gauge exhibits a phase transition. Above the critical number of fermion flavours the non-perturbative running coupling develops a plateau over a wide momentum range, and the propagators follow a power law behaviour for these momenta. Hereby, the critical number of quark flavours depends crucially on the beyond-tree-level tensor structures of the quark-gluon vertex.