Relationships Between Exact RGs and some Comments on Asymptotic Safety

Abstract

The standard flow equation for the effective average action can be derived from a Legendre transform of Polchinski's exact renormalization group equation. However, the latter is not well adapted for finding fixed-points with non-zero anomalous dimension. Instead, it is more convenient to use a modified version which ensures that the redundant coupling associated with the normalization of the field never appears in the action. Taking this as the starting point, a Legendre transform is constructed allowing a direct derivation of the corresponding flow equation for the effective average action. This equation is then used to exactly construct some illuminating though essentially trivial) asymptotically safe trajectories emanating from various non-unitary fixed-points. Finally, in the context of asympotically safe quantum gravity, it is pointed out that the standard argument that the anomalous dimension of Newton's constant is necessarily 2-d at a non-trivial fixed-point is incomplete. The implications of this are discussed.