An image KvBLL caloron gas model and confinement Original Research Article

A semi-classical model is developed to describe pure image Yang–Mills gluodynamics at finite temperature as a dilute, non-interacting gas of Kraan–van Baal–Lee–Lu calorons including the case of non-trivial holonomy. Temperature-dependent parameters of the model (asymptotic caloron holonomy, caloron density and caloron size distribution) are discussed from the point of view of lattice observations and of in-medium modifications of the one-loop caloron amplitude. Space-like string tensions running into plateaux at distances image are obtained and compared to lattice results in order to find more precisely the average caloron size. Then, the quark–antiquark free energy as predicted by the model is considered. In the confined phase a linear rise with the separation can be observed up to image, whereas it runs into plateaux above image. Screening effects in the adjoint potentials are observed together with an approximate Casimir scaling of the caloron contribution to the fundamental and adjoint forces. In Abelian projection, space-like percolation of monopoles is found in the confined phase only. Thus, taking the non-trivial holonomy into account, confinement properties of pure image Yang–Mills gluodynamics can be described by a semi-classical approach up to distances one order of magnitude larger than the caloron size.