Approximate Chiral Symmetry, in Medium Pion Mass, and the PI-Abnormal Nuclear State

Abstract

In an approximately chiral symmetric nuclear model consistent with the empirical nuclear data, we find that the medium pion mass approaches zero when the nuclear density approaches a critical value. At this critical density a chiral rotation occurs. The binding energy pernucleon jumps from about 16 MeV to 85 MeV. Since the chiral angle is not zero, we call this new state the pi-abnormal nuclear state. In this new state the pion mass becomes about 140 MeV again. Then it decreases with further increase of the nuclear density until it reaches another critical point. At this second point, the chiral angle reaches π. The pion mass starts rising. We identify this phase with the Lee–Wick's abnormal nuclear state.