Perturbative construction of the two-dimensional O(N) non-linear sigma model with ERG

We use the exact renormalization group (ERG) perturbatively to construct the Wilson action for the two-dimensional O(N) non-linear sigma model. The construction amounts to regularization of a non-linear symmetry with a momentum cutoff. A quadratically divergent potential is generated by the momentum cutoff, but its non-invariance is compensated by the jacobian of the non-linear symmetry transformation.Comment: 16 pages, 4 figure