Exploring lattice quantum chromodynamics by cooling

Abstract

The effect of cooling on a number of observables is calculated in SU(2) lattice gauge theory. The static quark-antiquark potential and spin-dependent interactions are studied, and the topological charge is monitored. The chiral symmetry breaking order parameter χχ and meson correlators are calculated using staggered fermions. Interactions on the distance scale of a few lattice spacings are found to be essentially eliminated by cooling, including the spin-dependent potentials. χχ and meson correlators up to time separations of several lattice spacings relax very quickly to their free-field values. At larger times, there is evidence of a difference between the pseudoscalar and vector channels. A fit to the pseudoscalar correlation function yields "mass" values about 2/3 (in lattice units) of the uncooled masses. These results raise the question of how to reconcile the large-time behavior of the hadron correlators with the fact that the spin-dependent potentials and χχ essentially disappear (in lattice units) after only a small amount of cooling.

Recombination of dyons into calorons inSU(2)lattice fields at low temperatures

“…It cannot be used for revealing the full topological structure of the QCD vacuum even if the latter is semi-classical to a certain extent. In particular, it considerably weakens the chiral condensate compared with its value for equilibrium fields [10]. Moreover, it is well-known that the Wilson action depends on the instanton (or caloron) scale-size.…”

Chiral symmetry breaking and cooling in lattice QCD

“…At present we have no explanation for the different behavior observed in the SU (2) and SU(3) calculations. One possibility is that the SU(2) calculation, which was done at β = 2.4, is just deeper in the weak coupling region than the SU(3) calculations done here at β = 5.7 and 5.9.…”

“…In Ref. [2] it was found that the spin-dependent potential and the chiral symmetry breaking order parameter disappear very quickly upon cooling. In a subsequent nonquenched SU(3) calculation by Edwards et al [3], it was found that cooling has a large effect on the hadron spectrum, tending, for example, to diminish spin-slittings.…”

“…Motivated by this work, a calculation was done in quenched SU(2) lattice gauge theory exploring the effect of cooling [2]. In Ref.…”

“…A calculation was done in quenched SU(3) lattice gauge theory to see if the different chiral symmetry breaking pattern observed in Ref. [2] and in Edwards et al [3] is due to the use of SU(2) versus SU (3) color or due to the quenched versus nonquenched nature of the simulation.…”