Renormalization-group theoretical reduction

It has been known for some time that singular perturbation and reductive perturbation can be unified from the renormalization-group (RG) theoretical point of view. However, renormalization-group approaches to singularly perturbed problems require explicit perturbation results, so they could be complicated practically. The approach proposed in this paper has considerably eliminated the need for explicit perturbation results, making the RG approach simpler than many conventional singular perturbation approaches. Consequently, we may assert that reductive extraction of global features of the problem is the essence of singular perturbation methods.