Abstract:In honor of Onsager's ninetieth birthday, we like to review some exact results obtained so far in the chiral Potts models and to translate these results into language more transparent to physicists, so that experts in Monte Carlo calculations, high and low temperature expansions, and various other methods, can use them.We shall pay special attention to the interfacial tension ǫ r between the k state and the k − r state. By examining the ground states, it is seen that the integrable line ends at a superwetting point, on which the relation ǫ r = r ǫ 1 is satisfied, so that it is energetically neutral to have one interface or more. We present also some partial results on the meaning of the integrable line for low temperatures where it lives in the non-wet regime. We make Baxter's exact results more explicit for the symmetric case. By performing a Bethe Ansatz calculation with open boundary conditions we confirm a dilogarithm identity for the low-temperature expansion which may be new.We propose a new model for numerical studies. This model has only two variables and exhibits commensurate and incommensurate phase transitions and wetting transitions near zero temperature. It appears to be not integrable, except at one point, and at each temperature there is a point, where it is almost identical with the integrable chiral Potts model.
KEY WORDS:Chiral Potts model; chiral clock model; star-triangle equations; Yang-Baxter equations; interfacial tension; wetting; superwetting; scaling; corrections to scaling; low-temperature expansions; dilogarithms; Bethe Ansatz.
INTRODUCTIONWhen Onsager published his solution of the two-dimensional Ising model in 1944, (1) this was almost instantly recognized as a milestone in the development of statistical mechanics. Many new developments were inspired by his results. On the other hand, Onsager's techniques were far ahead of his time and, when he announced his incredibly simple result for the spontaneous magnetization as a comment to a conference talk, (2,3) his paper Onsager's (only partly published) work on two-point functions in the Ising model got extended in 1966, (18−20) but it was only in 1973, when Wu, McCoy, Tracy, announced the Painlevé equation for the scaled two-point correlation, that the theory of the two-dimensional Ising model went beyond Onsager's level. Also, the first two-dimensional models solved that were more complicated than the Ising model were Lieb's ice model (24,25) of 1967 and Baxter's eight-vertex model (9) of 1973.Onsager's loop-algebra solution method was generalized only in 1985 when Von Gehlen and Rittenberg (26) solved the Dolan-Grady (27) criterium within a one-dimensional generalization of the quantum Potts model. The connection with Onsager's 1944 paper was noticed by Perk, (28,29) showing that the chiral Potts model (30,31,10) is the first genuine generalization of the Ising model, with its "superintegrable" case (32) solvable for two reasons: startriangle integrability (30,31,10) and loop-algebra integrability. (28,26) The chiral Potts...