By fixing the imaginary isospin chemical potential of three mass-degenerate quark flavors to mu_I = i4piT/3, where the dynamical-fermion theory acquires an exact Z(3) center symmetry like pure gauge theory, a finite-size scaling analysis of the rotated Polyakov loop shows the finite-temperature deconfinement transition is genuinely first order. Learners see how an exact center symmetry can be engineered in a theory with light quarks, how the moments of the order-parameter distribution (a susceptibility that scales with the volume, a skewness that crosses zero at criticality) diagnose the order of a transition, and how the deconfinement discontinuity imprints itself on the quark condensate.
This lattice QCD study examines three mass-degenerate quark flavors at an imaginary isospin chemical potential fixed to mu_I = i4piT/3, a special point where the theory acquires an exact Z(3) center …