The saga of the Ising susceptibility

B. M. McCoy, M. Assis, S. Boukraa, S. Hassani, J-M Maillard, W. P. Orrick, N. Zenine

Published 2010-03-03, updated 2010-03-11Version 2

We review developments made since 1959 in the search for a closed form for the susceptibility of the Ising model. The expressions for the form factors in terms of the nome $q$ and the modulus $k$ are compared and contrasted. The $\lambda$ generalized correlations $C(M,N;\lambda)$ are defined and explicitly computed in terms of theta functions for $M=N=0,1$.