This paper is a continuation of the authors' paper published in no. 3 of this journal in the previous year, where a detailed statement of the problem on the two-particle bound state spectrum of transfer matrices was given for a wide class of Gibbs fields on the lattice Z ν+1 in the high-temperature region (T 1). In the present paper, it is shown that for ν = 1 the so-called "adjacent" bound state levels (i.e., those lying at distances of the order of T −α , α > 2, from the continuous spectrum) can appear only for values of the total quasimomentum Λ of the system that satisfy the condition |Λ−Λ multare the quasimomentum values for which the symbol {ω Λ (k), k ∈ T 1 } has two coincident extrema. Conditions under which such levels actually appear are also presented.Key words: transfer matrices, bound state, Fredholm operator, total quasimomentum, adjacent level.In memory of A. N. Zemlyakov
Brief RemindersThis paper is a continuation of [1], where a detailed statement of the problem on the twoparticle bound state spectrum of transfer matrices was given for Gibbs fields (with compact spin space consisting of more than two elements and with arbitrary compactly supported interaction along the "spatial" directions) in the high-temperature region β = 1/T 1. Recall that, after several reductions, the original problem was reduced in [1] to the following problem. There is a family {H Λ , Λ ∈ T ν } of Hilbert spaces labeled by points of the ν -dimensional torus T ν (in [1], the symbol Λ denotes the total quasimomentum of two quasiparticles), dk). (Here dk is the normalized Haar measure on the torus T ν .) In each of the spaces H Λ , a self-adjoint operator T Λ acts according to the formulas