This tag is for questions which relates with the renormalization, an ensemble of techniques which serves to treat the infinities which appear in quantum field theory or statistical mechanics. Renormalization procedures are based on the requirement that certain physical quantities (such as the mass and charge of an electron) equal observed (experimental) values.
Renormalization, a collection of techniques in quantum field theory, the statistical mechanics of fields, and the theory of self-similar geometric structures, is the procedure in quantum field theory by which divergent parts of a calculation, leading to nonsensical infinite results, are absorbed by redefinition into a few measurable quantities, so yielding finite answers. The basic idea behind renormalization is that all effects of the very high-energy states in the Hilbert space on the low-energy behavior of the theory can be simulated by a set of new local interactions.
Also one can see the following :