Confinement from semiclassical gluon fields in SU(2) gauge theory

The infrared structure of SU(2) Yang-Mills theory is studied by means of lattice gauge simulations using a new constrained cooling technique. This method reduces the action while all Polyakov lines on the lattice remain unchanged. In contrast to unconstrained cooling, quark confinement remains intact. A study of the Hessian of the Yang-Mills action shows that low action (semi-)classical configurations can be achieved, with a characteristic splitting between collective modes and higher momentum modes. Besides confinement, the semiclassical configurations also support the topological susceptibility and generate spontaneous breakdown of chiral symmetry. We show that they possess a cluster structure of locally mainly (anti-)selfdual objects. By contrast to an instanton or a meron medium, the topological charge of individual clusters is smoothly distributed.