Semiclassical structure of (lattice) QCD at non-zero temperature: caloron solutions with nontrivial holonomy

At present, different models of the vacuum state are used to explain non-perturbative features of Quantum Chromodynamics. Instantons as carriers of topological charge are believed to be responsible for axial and chiral symmetry breaking, Abelian monopoles and/or centre vortices for quark confinement. The present project has the aim to verify, in lattice gauge theory simulations, a generalization of the semiclassical approach which promises to unify the carriers of topological charge with monopoles or dyons in finite temperature Yang-Mills theory. Such a synthesis seems to be viable since the discovery of caloron solutions with non-trivial asymptotic holonomy. The complete moduli space contains solutions which are dissociated into `instanton constituents' with variable action and topological charge. The possible relevance of such solutions has been overlooked in the past in ab-initio lattice investigations of topological structure. Lattice investigations of our own have given evidence for the existence of dyonic instanton constituents in SU(2) gluodynamics just below the deconfinement temperature. With the present project we want to strengthen joint efforts of groups at HU Berlin and ITEP Moscow, (1) to explore the dynamical relevance of these solutions at lower temperatures for SU(2) and to exclude it in the deconfined phase, (2) to find corresponding signatures for SU(3) gluodynamics and (3) to figure out the modifications in the presence of dynamical quarks.