Editing Cutoff (physics) (section)

==Effect on calculation==
A typical use of cutoffs is to prevent [[mathematical singularity|singularities]] from appearing during calculation. If some quantities are computed as [[integral]]s over energy or another physical quantity, these cutoffs determine the limits of integration. The exact physics is reproduced when the appropriate cutoffs are sent to zero or infinity. However, these integrals are often divergent – see [[IR divergence]] and [[UV divergence]] – and a cutoff is needed. The dependence of physical quantities on the chosen cutoffs (especially the ultraviolet cutoffs) is the main focus of the theory of the [[renormalization group]].