Key points are not available for this paper at this time.
The critical exponents, and the "crossover index" are computed for generalized classical Heisenberg models with n internal degrees of freedom as an exact expansion in =4-d (d is the number of space dimensions). Results are obtained to order ^2 for and to order ^3 for. The results to this order for the three-dimensional Ising case (n==1) are =1. 244 and =0. 037.
Kenneth G. Wilson (1972) studied this question.