Complex-temperature singularities of the susceptibility in the d = 2 Ising model: I. Square lattice
V. Matveev, Robert E. Shrock
Abstract
king model on a square lattice. From an analysis of low-temperature series expansions. we find evidence that, as one approaches the point U = us =- I (where U = e-") from within the complex extensions of the FM or AFM phases. the susceptibility has 3. divergent singularity of the farm,y- A:(l + u)-y: with exponent r: = i. The critical amplitude A: is calculated. Other critical exponents are found to be ci = cs = 0 and ps = $, so thY the scaling relation U: + 26, + y: = 2 is satisfied. However, using exact results for ps on the square, triangular, and honeycomb lattices, we show that universality is violated at this singularity: ps is lattice-dependent. Finally, from an analysis of spin-spin correlation functions, we demonstrate that the correlation length nnd hence susceptibility are finite GS one approaches the point I ( =-1 from within the symmetric phase. This is m n h e d by an explicit study of high-tempemture series expansions. We investigate the complex-temperature singularities of the susceptibility of the 1.