Critical behavior of anisotropic cubic systems

The critical behavior in zero field above Tc of ferromagnets or ferroelectrics with a Hamiltonian of cubic symmetry is studied, to order ε2, by exact renormalization-group techniques in d=4-ε dimensions with n-component spins. For ε=1, nY3, a crossover from isotropic (Heisenberg) to characteristic cubic behavior occurs, with the new value 2vC=1+[(n-1)3n]ε+[(n-1)324n3](17n2+290n-424)ε2+O(ε3), and cubic symmetry appearing in the four-spin correlation function. Experiments on structural phase transitions are considered briefly.