Gennady Voronov

The $SU\!\left(2\right)$ gauge theories with $N_{f}$ flavors of massless vector-like Dirac fermions transforming in the pseudo-real fundamental representation have an enhanced global chiral symmetry and a distinct symmetry breaking pattern. These theories are expected to be qualitatively different from quantum chromodynamics (QCD) in the infrared (IR), especially with respect to the properties of the Nambu-Goldstone bosons (NGB). Having the potential to elucidate many features of both known and conjectured strongly-coupled physics, these theories ought to be investigated. Here I study the six-flavor theory, which is expected to lie near the lower edge of the conformal window. A determination of whether this specific theory is inside the window holds the promise of revealing a great deal of the structure of this interesting class of theories. 

 

Toward this end, I compute the running gauge coupling in the non-perturbative Schroedinger functional (SF) scheme. This computation is performed numerically with lattice simulations of the $SU\!\left(2\right)$ lattice gauge theory with six flavors of stout-smeared Wilson fermions. I find no evidence for an infrared fixed point (IRFP) up through renormalized gauge couplings $\bar{g}^{2}$ of order $20$. This implies that the theory either is governed by an IRFP of considerable strength, unseen so far in non-supersymmetric gauge theories, or breaks its global chiral symmetries producing a large number of composite NGBs relative to the number of underlying degrees of freedom. Thus either of these phases exhibits novel behavior.