Scale dependence of local f_NL
  We consider possible scale-dependence of the non-linearity parameter f_NL in
local and quasi-local models of non-Gaussian primordial density perturbations.
In the simplest model where the primordial perturbations are a quadratic local
function of a single Gaussian field then f_NL is scale-independent by
construction. However scale-dependence can arise due to either a local function
of more than one Gaussian field, or due to non-linear evolution of modes after
horizon-exit during inflation. We show that the scale dependence of f_NL is
typically first order in slow-roll. For some models this may be observable with
experiments such as Planck provided that f_NL is close to the current
observational bounds.
