Grassmannian Sigma Models and Topological-Antitopological Fusion

We study the topological-antitopological fusion equations for supersymmetric sigma models on Grassmannian manifolds G(k,N). We find a basis in which the metric becomes diagonal and the $tt^*$ equations become tractable. The solution for the metric of G(k,N) can then be described in terms of the metric for the $CP^{N-1}$ models. The IR expansion helps clarify the picture of the vacua and gives the soliton numbers and masses. We also show that the $tt^*$ equation for G(k,N) in the large N limit is solvable, for any k.