Gaussian fluctuations for the magnetization of Lee-Yang ferromagnets at zero external field

The authors consider the fluctuations of the block spin magnetization normalized by the square root for the considered number of spins in a block Λ for Lee-Yang ferromagnets. It is established that the fluctuations are Gaussian when Λ upwards arrow Z/sup d/ at zero external field whenever the susceptibility is finite (i.e., above the critical temperature) and converges to the second derivative of the pressure at zero field. The validity of this fluctuation-dissipation condition is known to hold for a large class of Lee-Yang models, including, for instance, classical Heisenberg ferromagnets