Nonperturbative beta function of eight-flavor SU(3) gauge theory

TL;DR

This study investigates the nonperturbative behavior of the eight-flavor SU(3) gauge theory using lattice methods, finding no infrared fixed point and observing slow running of the coupling, indicating strong IR dynamics.

Contribution

First lattice calculation of the discrete beta function for Nf=8 flavors at strong couplings, using gradient flow and multiple lattice actions, extending previous results.

Findings

No IR fixed point up to g^2~14

Coupling runs slower than two-loop perturbation theory

Evidence of nontrivial IR dynamics in the 8-flavor system

Abstract

We present a new lattice study of the discrete beta function for SU(3) gauge theory with Nf=8 massless flavors of fermions in the fundamental representation. Using the gradient flow running coupling, and comparing two different nHYP-smeared staggered lattice actions, we calculate the 8-flavor step-scaling function at significantly stronger couplings than were previously accessible. Our continuum-extrapolated results for the discrete beta function show no sign of an IR fixed point up to couplings of g^2~14. At the same time, we find that the gradient flow coupling runs much more slowly than predicted by two-loop perturbation theory, reinforcing previous indications that the 8-flavor system possesses nontrivial strongly coupled IR dynamics with relevance to BSM phenomenology.