Speaker
Christof Gattringer
(Univ. of Graz, Austria)
Description
We explore the role of center symmetry and its explicit and spontaneous breaking in different parts of the QCD phase diagram. In particular the following issues are addressed: 1) In a fugacity expansion the grand canonical fermion determinant can be decomposed into canonical determinants with a fixed quark number. The canonical determinants have simple transformation properties under center transformations and we explore how different center sectors contribute to observables. 2) We study the behavior of local Polyakov loops in pure gluodynamics and full QCD. It is shown that spatial clusters may be identified where the phases of the local Polyakov loops have coherent values near the center elements. The transition to the deconfining phase is signaled by the onset of percolation. 3) An effective theory for the Polyakov loop with center symmetry breaking terms and a chemical potential is studied. The theory can be exactly mapped onto a dimer-monomer system where the sign problem is solved. We simulate the system with a worm algorithm and discuss its phase diagram and the consequences for the QCD phase diagram.
