Chiral symmetry for positive and negative parity nucleons

We investigate the role of chiral symmetry in the properties of positive and negative parity nucleons (N and N^*). When we consider two kinds of nucleons, two distinctive types of chiral assignment for N^* can be introduced. There are interesting differences between the two assignments in the properties of nucleons, which are studied using linear sigma models based on the two assignments. Behavior of N and N^* in the nuclear medium is also investigated using these linear models.