Anqi Cheng

Novel phase in SU(3) lattice gauge theory with 12 light fermions

We study the phase structure of SU(3) lattice gauge theory with

Scale-dependent mass anomalous dimension from Dirac eigenmodes

{N}_{f}=12

Improving the continuum limit of gradient flow step scaling

staggered fermions in the fundamental representation, for both zero and finite temperature at strong gauge couplings. For small fermion masses we find two transitions at finite temperature that converge to two well-separated bulk phase transitions. The phase between the two transitions appears to be a novel phase. We identify order parameters showing that the single-site shift symmetry of staggered fermions is spontaneously broken in this phase. We investigate the eigenvalue spectrum of the Dirac operator, the static potential and the meson spectrum, which collectively establish that this novel phase is confining but chirally symmetric. The phase is bordered by first-order phase transitions, and since we find the same phase structure with

Finite size scaling of conformal theories in the presence of a near-marginal operator

{N}_{f}=8

Determining the mass anomalous dimension through the eigenmodes of Dirac operator

fermions, we argue that the novel phase is most likely a strong-coupling lattice artifact, the existence of which does not imply IR conformality.

Mass anomalous dimension from Dirac eigenmode scaling in conformal and confining systems

A bstractWe investigate the eigenmodes of the massless Dirac operator to extract the scale-dependent fermion mass anomalous dimension γm(μ). By combining simulations on multiple lattice volumes, and when possible several gauge couplings, we are able to measure the anomalous dimension across a wide range of energy scales. The method that we present is universal and can be applied to any lattice model of interest, including both conformal or chirally broken systems. We consider SU(3) lattice gauge theories with Nf = 4, 8 and 12 light or massless fermions. The 4-flavor model behaves as expected for a QCD-like system and demonstrates that systematic effects are manageable in practical lattice calculations. Our 12-flavor results are consistent with the existence of an infrared fixed point, at which we predict the scheme-independent mass anomalous dimension

Bulk and finite-temperature transitions in SU(3) gauge theories with many light fermions

\gamma_m^{*}=0.32(3)

Reaching the chiral limit in many flavor systems

. For the 8-flavor model we observe a large anomalous dimension across a wide range of energy scales. Further investigation is required to determine whether Nf = 8 is chirally broken and walking, or if it possesses a strongly-coupled conformal fixed point.

Finite size scaling and the effect of the gauge coupling in 12 flavor systems

A bstractWe introduce a non-perturbative improvement for the renormalization group step scaling function based on the gradient flow running coupling, which may be applied to any lattice gauge theory of interest. Considering first SU(3) gauge theory with Nf = 4 massless staggered fermions, we demonstrate that this improvement can remove

Improved Lattice Renormalization Group Techniques

\mathcal{O}\left( {{a^2}} \right)