We have studied spin-spin correlation functions in the ordered phase of the
two-dimensional q-state Potts model with q=10, 15, and 20 at the
first-order transition point βt​. Through extensive Monte Carlo
simulations we obtain strong numerical evidence that the correlation length in
the ordered phase agrees with the exactly known and recently numerically
confirmed correlation length in the disordered phase: ξo​(βt​)=ξd​(βt​). As a byproduct we find the energy moments in the ordered phase
at βt​ in very good agreement with a recent large q-expansion.Comment: 11 pages, PostScript. To appear in Europhys. Lett. (September 1995).
See also http://www.cond-mat.physik.uni-mainz.de/~janke/doc/home_janke.htm