Quark confinement in C-periodic cylinders at temperatures above Tc

Due to the Gauss law, a single quark cannot exist in a periodic volume, while it can exist with C-periodic boundary conditions. In a C-periodic cylinder of cross section A = LxLy and length Lz ⪢ Lx,Ly containing deconfined gluons, regions of different high temperature Z(3) phases are aligned along the z-direction, separated by deconfined-deconfined interfaces. In this geometry, the free energy of a single static quark diverges in proportion to Lz. Hence, paradoxically, the quark is confined, although the temperature T is larger than Tc. At T ≈ Tc, the confined phase coexists with the three deconfined phases. The deconfined-deconfined interfaces can be completely or incompletely wet by the confined phase. The free energy of a quark behaves differently in these two cases. Our results imply that deconfined-deconfined interfaces are not just Euclidean artifacts, but have observable consequences in a system of hot gluons.