Reaching the chiral limit in many flavor systems

Abstract

We present a brief overview of our recent lattice studies of SU(3) gauge theory with N_f = 8 and 12 fundamental fermions, including some new and yet-unpublished results. To explore relatively unfamiliar systems beyond lattice QCD, we carry out a wide variety of investigations with the goal of synthesizing the results to better understand the non-perturbative dynamics of these systems. All our findings are consistent with conformal infrared dynamics in the 12-flavor system, but with 8 flavors we observe puzzling behavior that requires further investigation. Our new Monte Carlo renormalization group technique exploits the Wilson flow to obtain more direct predictions of a 12-flavor IR fixed point. Studies of N_f = 12 bulk and finite-temperature transitions also indicate IR conformality, while our current results for the 8-flavor phase diagram do not yet provide clear signs of spontaneous chiral symmetry breaking. From the Dirac eigenvalue spectrum we extract the mass anomalous dimension gamma_m, and predict gamma*_m = 0.32(3) at the 12-flavor fixed point. The N_f = 8 system again shows interesting behavior, with a large anomalous dimension across a wide range of energy scales. We use the eigenvalue density to predict the chiral condensate, and compare this approach with direct and partially-quenched measurements.

7 pages, 5 figures; Contribution to SCGT12 "KMI-GCOE Workshop on Strong Coupling Gauge Theories in the LHC Perspective", 4-7 Dec. 2012, Nagoya University

References in corpus (9)

• Observation of a new boson with mass near 125 GeV in pp collisions at sqrt(s) = 7 and 8 TeV
• Walking signals in Nf=8 QCD on the lattice
• Lattice study of infrared behaviour in SU(3) gauge theory with twelve massless flavours
• The bulk transition of QCD with twelve flavors and the role of improvement
• Confining force and running coupling with twelve fundamental and two sextet fermions
• The scalar spectrum of many-flavour QCD
• Conformal finite size scaling of twelve fermion flavors
• Lattice QCD with 12 Degenerate Quark Flavors
• MCRG study of 8 and 12 fundamental flavors

Cited by in corpus (8)

• Nonperturbative beta function of twelve-flavor SU(3) gauge theory
• Nonperturbative beta function of eight-flavor SU(3) gauge theory
• Improving the continuum limit of gradient flow step scaling
• Explorations beyond dilaton chiral perturbation theory in the eight-flavor SU(3) gauge theory
• Emergent strongly coupled ultraviolet fixed point in four dimensions with 8 Kähler-Dirac fermions
• Stealth dark matter confinement transition and gravitational waves
• Walking in the 3-dimensional large $N$ scalar model
• Taming lattice artifacts with Pauli--Villars fields