ADJOINT "QUARK" COLOR FIELDS IN FOUR-DIMENSIONAL LATTICE GAUGE THEORY: VACUUM SCREENING AND PENETRATION

Abstract

The fields generated by ``quarks'' in the adjoint representation of SU(2) color are analyzed in the scaling region of the four-dimensional lattice theory. Evidence of vacuum screening of adjoint quarks is obtained from a comparison of quark-antiquark ($Q\bar{Q}$) flux-tubes for quarks in the adjoint (``isospin'' $j=1$) and fundamental ($j=1/2$) representations. The component ${\mathcal{E}}_j$ of the color-electric field strength in the direction parallel to the $Q\bar{Q}$ axis is calculated. Near the quarks the ratio of fields ${\mathcal{E}}_{j=1}/{\mathcal{E}}_{j=1/2}$ approaches the value 8/3, which is equal to the ratio of SU(2) Casimirs. In between the quarks, the ratio falls well below 8/3 at large $R$. ${\mathcal{E}}_j$ also falls off rapidly as a function of distance $x_{\perp }$ perpendicular to the $Q\bar{Q}$ axis. However, the ratio ${\mathcal{E}}_{j=1}/{\mathcal{E}}_{j=1/2}$ depends very weakly on $x_{\perp }$. The flux-tubes in the two representations thus appear to have very similar cross-sections. This result could imply that the QCD vacuum is dual to a type I superconductor.

Comments: 7 pages plus 8 figures in 2 postscript files (uuencoded)