UNIVERSAL SURFACE-TENSION AND CRITICAL-ISOTHERM AMPLITUDE RATIOS IN 3DIMENSIONS

The universal surface-tension and critical-isotherm amplitude ratios a re studied numerically for three-dimensional Ising models. Modern esti mates of the critical temperature and exponents allow reliable evaluat ion of the critical surface-tension amplitude, K, using recent Monte C arlo data for the simple cubic lattice. Likewise, the amplitudes C-c, for the susceptibility and, f(1)(c), for the second-moment correlation length, on the critical isotherm have been re-estimated using existin g series expansions. The method of inhomogeneous differential approxim ants also yields a direct estimate of the correction-to-scaling expone nt, theta(c), on the critical isotherm which, via scaling, corresponds to the thermal correction exponent theta = 0.55 +/- 5; this supports previous estimates and the stronger conclusion theta = 0.54 +/- 3. For the universal ratios, we estimate K(f(1)(-))(2) = 0.096(5) +/- 2, C-c delta/((BC+)-C-delta-1)(1/delta) = 0.93 +/- 2(5), and (C+/C-c)(f(1)(c )/f(1)(+))(2-eta) = 1.17 +/- 2, where B, f(1)(-), and C+ are the ampli tudes of the spontaneous magnetization, and (second moment) correlatio n length, and of the susceptibility above T-c.