Alternatively, the critical O ( N ) model can be constructed as the ε ε → → 1 limit of Wilson-Fisher fixed point in d = 4 − − ε ε dimensions. At ε ε = 0 , the Wilson-Fisher fixed point becomes the tensor product of N free scalars with dimension Δ Δ = 1 . For 0 < ε ε < 1 the model in question is non-unitary.