Physical Review Letters
Order-Parameter Distribution Function of Finite O(n) Symmetric Systems
Chen Xs, V. Dohm, Norbert Schultka
Abstract
We present analytic and numerical studies of the order-parameter distribution function near the critical point of $O(n)$ symmetric three-dimensional (3D) systems in a finite geometry. The distribution function is calculated within the ${\ensuremath{\phi}}^{4}$ field theory for a 3D cube with periodic boundary conditions by means of a new approach that appropriately deals with the Goldstone modes below ${T}_{c}$. Good agreement is found with new Monte Carlo data for the distribution function of the magnetization of the 3D $\mathrm{XY}$ $(n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2)$ and Heisenberg $(n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3)$ models.