Three-$\alpha$ configurations in the $0^{+}$ states of $^{12}\mathrm{C}$

Geometric configurations of three-$\alpha$ particles in the ground- and first-excited $J^\pi=0^+$ states of $^{12}$C are discussed within two types of $\alpha$-cluster models which treat the Pauli principle differently. Though there are some quantitative differences especially in the internal region of the wave functions, equilateral triangle configurations are dominant in the ground state, while in the first excited $0^+$ state isosceles triangle configurations dominate, originating from $^8{\rm Be}+\alpha$ configurations.