Patrick O. Bowman

Infinite Volume and Continuum Limits of the Landau-Gauge Gluon Propagator

We extend a previous improved action study of the Landau gauge gluon propagator, by using a variety of lattices with spacings from a = 0.17 to 0.41 fm, to more fully explore finite volume and discretization effects. We also extend a previously used technique for minimizing lattice artifacts, the appropriate choice of momentum variable or “kinematic correction”, by considering it more generally as a “tree-level correction”. We demonstrate that by using tree-level correction, determined by the tree-level behavior of the action being considered, it is possible to obtain scaling behavior over a very wide range of momenta and lattice spacings. This makes it possible to explore the infinite volume and continuum limits of the Landau-gauge gluon propagator.

Unquenched quark propagator in Landau gauge

[...] We present an unquenched calculation of the quark propagator in Landau gauge with 2� 1 flavors of dynamical quarks. We use configurations generated with an improved staggered (‘‘Asqtad’’) action by the MILC Collaboration. This quark action has been seen to have excellent rotational symmetry and scaling properties in the quenched quark propagator. Quenched and dynamical calculations are performed on a 20 3 � 64 lattice with a nominal lattice spacing of a � 0:125 fm. The matched quenched and dynamical lattices allow us to investigate the relatively subtle sea-quark effects, and even in the quenched case the physical volume of these lattices gives access to lower momenta than our previous study. We calculate the quark mass function and renormalization function for a variety of valence and sea-quark masses.

Unquenched gluon propagator in Landau gauge

[...] Using lattice quantum chromodynamics ~QCD! we perform an unquenched calculation of the gluon propagator in Landau gauge. We use configurations generated with the AsqTad quark action by the MILC collaboration for the dynamical quarks and compare the gluon propagator of quenched QCD ~i.e., the pure Yang-Mills gluon propagator! with that of 211 flavor QCD. The effects of the dynamical quarks are clearly visible and lead to a significant reduction of the nonperturbative infrared enhancement relative to the quenched case.

Scaling behavior and positivity violation of the gluon propagator in full QCD

The Landau-gauge gluon propagator is studied using the coarse and fine dynamical MILC configurations. The effects of dynamical quarks are clearly visible and lead to a reduction of the nonperturbative infrared enhancement relative to the quenched case. Lattice spacing effects are studied and found to be small. The gluon spectral function is shown to clearly violate positivity in both quenched and full QCD.

Infrared behavior of the gluon propagator on a large volume lattice

The first calculation of the gluon propagator using an

Scaling behavior of the quark propagator in full QCD

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

Overlap quark propagator in Landau gauge

improved action with the corresponding

Landau-gauge condensates from the quark propagator on the lattice

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

Quark propagator in Landau and Laplacian gauges with overlap fermions

improved Landau gauge fixing condition is presented. The gluon propagator obtained from the improved action and improved Landau gauge condition is compared with earlier unimproved results on similar physical lattice volumes of

Infrared and ultraviolet properties of the Landau gauge quark propagator

{3.2}^{3}\ifmmode\times\else\texttimes\fi{}6.4{\mathrm{fm}}^{4}.