Chuan-Xin Cui, Jin-Yang Li, Shinya Matsuzaki, Mamiya Kawaguchi, Akio Tomiya
2021年6月10日
We find that the chiral phase transition (chiral crossover) in QCD at
physical point is triggered by big imbalance among three fundamental quantities
essential for the QCD vacuum structure: susceptibility functions for the chiral
symmetry, axial symmetry, and the topological charge. The balance, dobbed the
QCD trilemma, is unavoidably violated when one of the magnitudes among them is
highly dominated, or suppressed. Based on a three-flavor Nambu-Jona-Lasinio
model, we explicitly evaluate the amount of violation of the QCD trilemma at
physical point, and show that the violation takes place not only at vacuum, but
even in a whole temperature regime including the chiral crossover epoch. This
work confirms and extends the suggestion recently reported from lattice QCD
with 2 flavors on dominance of the axial and topological susceptibilities left
in the chiral susceptibility at high temperatures. It turns out that the
imbalance is essentially due to the flavor symmetry violation of the lightest
three flavors. The violation of QCD trilemma and its flavor dependence can be
tested by lattice simulations with 2 + 1 flavors in the future, and would also
give a new guiding principle to deeper understand the QCD phase structure, such
as the Columbia plot, including possible extension with external fields.