"Irreversibility" of the flux of the renormalization group in a 2D field theory
Zomolodchikov A. B.
There exists a function Ó (g) of the coupling constant g in a 2D renorrnalizable field theory which decreases monotonically under the influence of a renormalization-group transformation. This function has constant values only at fixed points, where Ó is the same as the central charge of a Virasoro algebra of the corresponding conformal field theory.