The isotropic Heisenberg chain of arbitrary spin by direct solution of the Baxter equation

The method of separation of variables (SoV) is applied to the spectral problem of the isotropic Heisenberg model. The Baxter difference equation is resolved by means of a special quasiclassical asymptotic expansion. States are identified using of multiplicities of limiting values of the Bethe parameters. application, the string limit of the three-particle sector is investigated. String solutions are singled out and classified. There is a set of solutions. Some of these solutions demonstrate string behavior. The number of solution demonstrating string behavior is small with respect to the total number of solutions.