On the surfaces associated with $mathbb{C}P^{N-1}$ models

We study certain new properties of 2D surfaces associated with the $\mathbb{C}P^{N-1}$ models and the wave functions of the corresponding linear spectral problem. We show that $su(N)$-valued immersion functions expressed in terms of rank-1 orthogonal projectors are linearly dependent, but they span an $(N-1)$-dimensional subspace of the Lie algebra $su(N)$. Their minimal polynomials are cubic, except for the holomorphic and antiholomorphic solutions, for which they reduce to quadratic trinomials. We also derive the counterparts of these relations for the wave functions of the linear spectral problems. In particular, we provide a relation between the wave functions, which results from the partition of unity into the projectors. Finally, we show that the angle between any two position vectors of the immersion functions, corresponding to the same values of the independent variables, does not depend on those variables.

💡 Research Summary

The paper investigates geometric surfaces that arise from the two‑dimensional $\mathbb{C}P^{N-1}$ sigma model and the associated linear spectral problem. The authors start by introducing a set of rank‑one orthogonal projectors $P_k$ ($k=0,\dots ,N-1$) which satisfy the completeness relation $\sum_{k=0}^{N-1}P_k=\mathbf{1}$ and the orthogonality $P_iP_j=\delta_{ij}P_i$. Using these projectors they construct $su(N)$‑valued immersion functions (often called “Weierstrass‑type” representations) as
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