Curves of Marginal Stability in Two-Dimensional CP(N-1) Models with Z_N-Symmetric Twisted Masses

We consider curves of marginal stability (CMS) in CP(N-1) models in two dimensions with N = (2, 2) supersymmetry. In these theories, one can introduce twisted mass terms. The BPS spectrum has different number of states in the weak and strong coupling regimes. This spectral restructuring can be explained by the fact that two regimes are separated by CMS on which some BPS states decay. We focus on a special case of Z_N-symmetric twisted masses. In this case, the general solution due to Dorey greatly simplifies, and CMS can be found explicitly. For small-$N$ values numerical results are presented. In the large-N limit, we find CMS analytically up to ln N /N corrections.