Structure of ground and excited states of ¹²C

We studied the ground and excited states of $^{12}$C based on variational calculations after spin-parity projection in a framework of antisymmetrized molecular dynamics(AMD). The calculations systematically reproduce various experimental data. It was found that the sub-shell closure and SU(3)-limit $3\alpha$ cluster components are contained in the ground state, while various $3\alpha$ cluster structures develop in the excited states. We discussed effects of $\alpha$ breaking and show the importance of coexistence of the cluster and shell-model-like aspects.