J. Cizek et P. Bracken, TRANSFORMATION OF THE BETHE EQUATIONS FOR FINITE CYCLES INTO SECULAR POLYNOMIALS IN ENERGY, Physical review letters, 77(2), 1996, pp. 211-214
The study of spin Hamiltonians is facilitated by the use of the Bethe
equations. Up to now, these equations were primarily used for the stud
y of the energy of the lowest state of a given symmetry. In this paper
, we would like to show that there is a technique by which these equat
ions for finite cycles can be transformed into an algebraic equation f
or the energy in which the coefficients are polynomials in the couplin
g constant, or just numbers.From this algebraic equation, we can get a
ll energies of a given symmetry in a straightforward way.