Abstract
Singularities in the d=2 Ashkin-Teller model are analyzed by writing down flow equations based upon the Gaussian model in the presence of suitable fields. A scaling function for the coherence length, ξ, is set up in terms of coordinates δ and t which describe deviations from the four-state Potts point. At that point, ξ depends on the reduced temperature as ξ1|t|23×|lnt|12.