arXiv:cond-mat/9705086 · Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics
Two-point correlation function of three-dimensional O(N) models: The critical limit and anisotropy
Massimo Campostrini B, Andrea Pelissetto C, Paolo Rossi, Ettore Vicari
Abstract
In three-dimensional $O(N)$ models, we investigate the low-momentum behavior of the two-point Green's function $G(x)$ in the critical region of the symmetric phase. We consider physical systems whose criticality is characterized by a rotationally invariant fixed point. Several approaches are exploited, such as strong-coupling expansion of lattice $N$-vector model, and $1/N$ expansion, field-theoretical methods within the ${\ensuremath{\varphi}}^{4}$ continuum formulation. Non-Gaussian corrections to the universal low-momentum behavior of $G(x)$ are evaluated, and found to be very small. In nonrotationally invariant physical systems with $O(N)$-invariant interactions, the vanishing of the spatial anisotropy approaching the rotationally invariant fixed point is described by a critical exponent $\ensuremath{\rho}$, which is universal and is related to the leading irrelevant operator breaking rotational invariance. At $N=\ensuremath{\infty}$ one finds $\ensuremath{\rho}=2$. We show that, for all values of $N>~0$, $\ensuremath{\rho}\ensuremath{\simeq}2$.