Phase structure of CPN-1 model with topological term

The CPN-1 model with the topological term is numerically studied. The topol ogical charge distribution P(Q) is calculated and then transformed to the p artition function Z(theta) as a function of a parameter. In the strong coup ling region, P(Q) shows a gaussian behavior, which indicates a first order phase transition at a = pi. In the weak coupling region, P(Q) deviates from gaussian. A bending behavior of resulting F(theta) at theta not equal pi, which might be a signal of a first order phase transition, could be misled by large errors coming from the Fourier-transform of P(Q). Results are show n mainly for the CP3 case.