Zero of the discrete beta function in SU(3) lattice gauge theory with color sextet fermions

TL;DR

This study investigates the running coupling in SU(3) lattice gauge theory with sextet fermions, finding evidence of an infrared fixed point through the sign change of the discrete beta function near g^2=2.0.

Contribution

First lattice calculation of the discrete beta function in SU(3) with sextet fermions indicating a possible infrared fixed point.

Findings

Discrete beta function changes sign near g^2=2.0

Evidence suggests an infrared-attractive fixed point

Results are consistent across different rescaling factors

Abstract

We have carried out a Schrodinger functional (SF) calculation for the SU(3) lattice gauge theory with two flavors of Wilson fermions in the sextet representation of the gauge group. We find that the discrete beta function, which governs the change in the running coupling under a discrete change of spatial scale, changes sign when the SF renormalized coupling is in the neighborhood of g^2=2.0. The simplest explanation is that the theory has an infrared-attractive fixed point, but more complicated possibilities are allowed by the data. While we compare rescalings by factors of 2 and 4/3, we work at a single lattice spacing.