Running coupling and mass anomalous dimension of SU(3) gauge theory with two flavors of symmetric-representation fermions

TL;DR

This study measures the running coupling and mass anomalous dimension of SU(3) gauge theory with two symmetric-representation fermions using improved lattice techniques, finding slow coupling evolution and a small anomalous dimension, with no evidence of an infrared fixed point.

Contribution

It provides the first lattice measurement of the running coupling and anomalous dimension for this theory using hypercubic smeared links, clarifying lattice artifacts and the nature of the fixed point.

Findings

Coupling runs more slowly than asymptotic freedom predicts.

No fixed point observed before a first order transition.

Mass anomalous dimension is small, gamma_m < 0.6.

Abstract

We have measured the running coupling constant of SU(3) gauge theory coupled to Nf=2 flavors of symmetric representation fermions, using the Schrodinger functional scheme. Our lattice action is defined with hypercubic smeared links which, along with the larger lattice sizes, bring us closer to the continuum limit than in our previous study. We observe that the coupling runs more slowly than predicted by asymptotic freedom, but we are unable to observe fixed point behavior before encountering a first order transition to a strong coupling phase. This indicates that the infrared fixed point found with the thin-link action is a lattice artifact. The slow running of the gauge coupling permits an accurate determination of the mass anomalous dimension for this theory, which we observe to be small, gamma_m < 0.6, over the range of couplings we can reach. We also study the bulk and finite-temperature phase transitions in the strong coupling region.