2014/11/18 by Híromichi Nishimura, Hiromichi Nishimura, Michael C. Ogilvie +1
Physics and Astronomy · #Deconfinement #Exponential decay #Geometry #High-Energy Particle Collisions Research #Lattice QCD #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #Quantum mechanics #Quark #Saddle #Saddle point #hep-lat #hep-ph #nucl-th
paper · pdf · doi:10.1103/physrevd.91.054004
published as Phys. Rev. D 91, 054004 (2015) · 33 pages, 20 figures
arxiv created 2014/11/18 · openalex publication_date 2015/03/03 · arxiv updated 2015/03/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The properties and consequences of complex saddle points are explored in phenomenological models of QCD at nonzero temperature and density. Such saddle points are a consequence of the sign problem and should be considered in both theoretical calculations and lattice simulations. Although saddle points in finite-density QCD are typically in the complex plane, they are constrained by a symmetry that simplifies analysis. We model the effective potential for Polyakov loops using two different potential terms for confinement effects and consider three different cases for quarks: very heavy quarks, massless quarks without modeling of chiral symmetry breaking effects, and light quarks with both deconfinement and chiral symmetry restoration effects included in a pair of Polyakov-Nambu-Jona Lasinio models. In all cases, we find that a single dominant complex saddle point is required for a consistent description of the model. This saddle point is generally not far from the real axis; the most easily noticed effect is a difference between the Polyakov loop expectation values ⟨TrFP⟩ and ⟨TrFP^\ifmmode†\else\textdagger\fi⟩, and that is confined to a small region in the \ensuremathμ\ensuremath-T plane. In all but one case, a disorder line is found in the region of critical and/or crossover behavior. The disorder line marks the boundary between exponential decay and sinusoidally modulated exponential decay of correlation functions. Disorder line effects are potentially observable in both simulation and experiment. Precision simulations of QCD in the \ensuremathμ\ensuremath-T plane have the potential to clearly discriminate between different models of confinement.