Phase transition in the three-dimensional $O(N)\otimes O(M)$ model: a Monte Carlo study

Using Monte Carlo simulations, we consider the lattice version of the $O(N)\otimes O(M)$ sigma model for $2\leq M\leq4$ and $M\leq N \leq8$. We find a continuous transition for $N\geq M+4$. Estimates of the critical exponents for cases of second-order and weak first-order transitions are found. For $M=2$ our estimates of the exponents and marginal dimensionality $N_c^+(M)$ are in good agreement with the results of the non-perturbative renormalization group approach. For $M\geq2$ we find estimates of the exponents and marginal dimensionality between the values obtained in the first and second orders of the large-N expansion. To complete the picture, we also consider the usual $O(N)$ model ($M=1$).

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