A relation between the temperature exponents of the eight-vertex and q-state Potts model

The mapping of the critical points in the q-state model for q<or=4 onto the Baxter line in the eight-vertex model makes it possible, by a comparison of the exactly known critical exponent yT8v with the approximately known values for yTP, to conjecture the relation (yT8v-2)(yTP-3)=3. This relation confirms weak universality.