Renormalization group  From Wikipedia, the free encyclopedia
Jump to: navigation, search  In theoretical physics, the
renormalization group (RG) refers to a mathematical apparatus
that allows systematic investigation of the changes of a
physical system as viewed at different distance scales. In
particle physics, it reflects the changes in the underlying
force laws (codified in a quantum field theory) as the energy
scale at which physical processes occur varies, energy/momentum
and resolution distance scales being effectively conjugate under
the uncertainty principle (cf. Compton wavelength).  A change in
scale is called a "scale transformation". The renormalization
group is intimately related to "scale invariance" and "conformal
invariance", symmetries in which a system appears the same at
all scales (so-called self-similarity). (However, note that
scale transformations are included in conformal transformations,
in general: the latter including additional symmetry generators
associated with special conformal