Critical behavior of the antiferromagnetic Heisenberg model on a stacked triangular lattice

We estimate, using a large-scale Monte Carlo simulation, the critical exponents of the antiferromagnetic Heisenberg model on a stacked triangular lattice. We obtain the following estimates: γ/ν= 2.011 ±0.014, ν= 0.585 ±0.009. These results contradict a perturbative 2 + ϵ Renormalization Group calculation that points to Wilson-Fisher O(4) behaviour. While these results may be coherent with 4 - ϵ results from Landau-Ginzburg analysis, they show the existence of an unexpectedly rich structure of the Renormalization Group flow as a function of the dimensionality and the number of components of the order parameter.