Bethe Ansatz for XXX chain with negative spin

Abstract

[Formula: see text] spin chain with spin [Formula: see text] appears as an effective theory of Quantum Chromodynamics. It is equivalent to lattice nonlinear Schroediger’s equation: interacting chain of harmonic oscillators [bosonic]. In thermodynamic limit each energy level is a scattering state of several elementary excitations [lipatons]. Lipaton is a fermion: it can be represented as a topological excitation [soliton] of original [bosonic] degrees of freedom, described by the group [Formula: see text]. We also provide the CFT description (including local quenches) and Yang–Yang thermodynamics of the model.