We have measured the running coupling constant of SU(3) gauge theory coupled to $N_f=2$ flavors of symmetric representation fermions, using the Schrödinger 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, ${\gamma }_m\lesssim 0.6$, over the range of couplings we can reach. We also study the bulk and finite-temperature phase transitions in the strong coupling region.

• Received 9 June 2010

DOI:https://doi.org/10.1103/PhysRevD.82.054503