Speaker
Description
We examine the role of the $U(1)_A$ anomaly in a parity doublet model of nucleons which include the chiral variant and invariant masses.
Our model expresses the $U(1)_A$ anomaly by the Kobayashi-Maskawa-'t\,Hooft (KMT) interaction in the mesonic sector.
After examining the roles of the KMT term in vacuum, we discuss its impacts on nuclear equations of state (EOS).
The $U(1)_A$ anomaly increases the masses of the $\eta'$ and $\sigma$ mesons and enhances the chiral symmetry breaking.
Also, the $U(1)_A$ anomaly enlarges the energy difference between chiral symmetric and symmetry broken vacuum;
in turn, the chiral restoration at high density adds
a larger energy density (often referred as a bag constant) to EOSs than in the case without the anomaly, leading to softer EOSs.
