New families of flows between two-dimensional conformal field theories

We present evidence for the existence of infinitely-many new families of re normalisation group Rows between the nonunitary minimal models of conformal field theory. These are associated with perturbations by the phi(21) and p hi(15) operators, and generalise a family of flows discovered by Martins. I n all of the new hows, the finite-volume effective central charge is a nonm onotonic function of the system size. The evolution of this effective centr al charge is studied by means of a nonlinear integral equation, a massless variant of an equation recently found to describe certain massive perturbat ions of these same models. We also observe that a similar nonmonotonicity a rises in the more familiar phi(13) perturbations, when the flows induced ar e between nonunitary minimal models. (C) 2000 Elsevier Science B.V. All rig hts reserved.