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Quadrics on Complex Riemannian Spaces of Constant Curvature, Separation of Variables and the Gaudin Magnet

We consider integrable systems that are connected with orthogonal separation of variables in complex Riemannian spaces of constant curvature. An isomorphism with the hyperbolic Gaudin magnet, previously pointed out by one of us, extends to coordinates of this type. The complete classification of these separable coordinate systems is provided by means of the corresponding $L$-matrices for the Gaudin magnet. The limiting procedures (or $ε$ calculus) which relate various degenerate orthogonal coordinate systems play a crucial result in the classification of all such systems.