Adjoint “quarks” on coarse anisotropic lattices: Implications for string breaking in full QCD

A detailed study is made of four dimensional SU(2) gauge theory with static adjoint “quarks” in the context of string breaking. A tadpole-improved action is used to do simulations on lattices with coarse spatial spacings as, allowing the static potential to be probed at large separations at a dramatically reduced computational cost. Highly anisotropic lattices are used, with fine temporal spacings at, in order to assess the behavior of the time-dependent effective potentials. The lattice spacings are determined from the potentials for quarks in the fundamental representation. Simulations of the Wilson loop in the adjoint representation are done, and the energies of magnetic and electric “gluelumps” (adjoint quark-gluon bound states) are calculated, which set the energy scale for string breaking. Correlators of gauge-fixed static quark propagators, without a connecting string of spatial links, are analyzed. Correlation functions of gluelump pairs are also considered; similar correlators have recently been proposed for observing string breaking in full QCD and other models. A thorough discussion of the relevance of Wilson loops over other operators for studies of string breaking is presented, using the simulation results presented here to support a number of new arguments.