Topology in Strong Coupling

The lattice CP^N-1 model at nonzero θ is analyzed by a strong-coupling expansion. At θ=π, CP is spontaneously broken and the theory ceases to confine. The θ dependence of several quantities is computed and the correlation length is shown to increase with θ. Most of the results apply not only to the CP^N-1 model (for all values of N) but to other two-dimensional nonlinear σ models as well.