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Invariant recurrence relations for CP^(N-1) models

In this paper, we present invariant recurrence relations for the completely integrable CP^(N-1) Euclidean sigma model in two dimensions defined on the Riemann sphere S^2 when its action functional is finite. We determine the links between successive projection operators, wave functions of the linear spectral problem, and immersion functions of surfaces in the su(N) algebra together with outlines of the proofs. Our formulation preserves the conformal and scaling invariance of these quantities. Certain geometrical aspects of these relations are described. We also discuss the singularities of meromorphic solutions of the CP^(N-1) model and show that they do not affect the invariant quantities. We illustrate the construction procedure through the examples of the CP^2 and CP^3 models.