Nonmicroscopic and microscopic descriptions of condensate states in the 12C and 16O nuclei

C-12 and O-16 nuclei are investigated within nonmicroscopic and microscopic theoretical frameworks, respectively. For the C-12 nucleus viewed as a 3 alpha system, 3-body Faddeev equations are solved in configuration space. Positions of the resonant states are obtained through the complex scaling method. We show that the nonlocal potential developed by Z. Papp and S. Moszkowski appears to be well-adapted to study 3 alpha system. In particular, we show evidence for C-12 states of positive-parity which share common features with the well-known 0(2)(+) Hoyle state, currently interpreted as a condensate state. For the O-16 nucleus, a C-12+alpha multicluster generator coordinate method is used to solve the 16-nucleon problem. The O-16 nucleus is described by four alpha cluster. We comment the difficulty to interpret broad resonant states. The phase-shift analysis of the C-12(0(2)(+)) + alpha channel reveals the existence of two 0(+) states located above the 4 alpha threshold which can be interpreted as condensate states.