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HK: Fachverband Physik der Hadronen und Kerne

HK 57: Heavy-Ion Collisions and QCD Phases XIII

HK 57.2: Vortrag

Freitag, 3. April 2020, 11:30–11:45, J-HS G

Quark Number and Electric Flux in QCD — •Milad Ghanbarpour and Lorenz von Smekal — Institut für Theoretische Physik, Justus-Liebig-Universität Gießen, Deutschland

In pure SU(3)-gauge theory the free energy of a static quark in a finite volume can be rigorously defined to account for its electric flux, via suitable combinations of twisted boundary conditions relative to an enlarged ensemble with all temporal twists. In the infinite volume limit, it diverges in the confined phase and vanishes above the deconfinement phase transition. In full QCD with dynamical quarks, the situation is less clear. A straightforward definition via pseudo-canonical ensembles with quark numbers N_q that are not multiples of three fails, the corresponding partition functions vanish due to the Roberge-Weiss symmetry already in a finite volume. Such quark numbers are inconsistent with periodic boundary conditions. Therefore we first need to understand the correct boundary conditions to account for the elecrtic flux and the entanglement entropy of subsystems with N_q 3 ≠ 0. Here, we approach this problem from the heavy-dense limit of QCD at fixed quark number. The analogue system is a 3-states Potts model in three dimensions. In its naive formulation, the system suffers from a sign problem which can be solved in this case, however (see Alexandru et al., Phys. Rev. D 97 (2018) 114503). The solution consists of utilizing a cluster algorithm and improved estimators. Our first goal therefore is to adapt this scheme for non-periodic boundary conditions so that we can describe ensembles with arbitrary quark numbers in a finite volume. In this talk we review the current status of the project.