Physics of Scale Activities

1961
Padé approximants
Exact series expansions were most useful for high temperatures, where the coefficients were uniformly positive and the convergence behavior could be demonstrated fairly directly. For low temperature expansions it was more difficult to identify convergence patterns, since the sign of the coefficients was inconsistent. Baker revived Padé's method of approximating the ratio [L,M] of two polynomials of degree L and M so that a given expansion F(x) which contained many singularities (poles) could be represented as F(x) = [L,M] + terms of order (L+M+1) and higher. Baker showed that the Padé approximants could be used in many instances to continue a series expansion analytically to the critical point, thus yielding more accurate critical exponents. In particular, Baker analyzed spontaneous magnetization and found a value for ß roughly equal to 0.30.

Primary:

George A. Baker, Jr., "Application of the Padé approximant method to the investigation of some magnetic properties of the Ising model," Phys. Rev. 124 (1961): 768- 774.

Secondary:

Brush 1983, 253.

Domb 1996, 165.

Fisher 1967, 687.
--Karl Hall