The antiferromagnetic critical point of the Potts model on the square lattice
was identified by Baxter as a staggered integrable six-vertex model. In this
work, we investigate the integrable structure of this model. It enables us to
derive some new properties, such as the Hamiltonian limit of the model, an
equivalent vertex model, and the structure resulting from the Z_2 symmetry.
Using this material, we discuss the low-energy spectrum, and relate it to
geometrical excitations. We also compute the critical exponents by solving the
Bethe equations for a large lattice width N. The results confirm that the
low-energy spectrum is a collection of continua with typical exponent gaps of
order 1/(log N)^2.Comment: 46 pages, 31 figure
