On the effective Lagrangian of CP^(N-1) models in the large N limit
  The effective low energy Lagrangian of $CP^{N-1}$ models in $d < 4$ dimensions can be constructed in the large $N$ limit by solving the saddle point equations in the presence of a constant field strength. The two dimensional case is explicitly worked out and possible applications are briefly discussed. 
Paolo Rossi
hep-th