Chiral Potts Rapidity Curve Descended from Six-vertex Model and Symmetry   Group of Rapidities
  In this paper, we present a systematical account of the descending procedure from six-vertex model to the $N$-state chiral Potts model through fusion relations of $\tau^{(j)}$-operators, following the works of Bazhanov-Stroganov and Baxter-Bazhanov-Perk. A careful analysis of the descending process leads to appearance of the high genus curve as rapidities' constraint for the chiral Potts models. Full symmetries of the rapidity curve are identified, so is its symmetry group structure. By normalized transfer matrices of the chiral Potts model, the $\tau^{(2)}T$ relation can be reduced to functional equations over a hyperelliptic curves associated to rapidities, by which the degeneracy of $\tau^{(2)}$-eigenvalues is revealed in the case of superintegrable chiral Potts model. 
Shi-shyr Roan