Strong scale dependent bispectrum in the Starobinsky model of inflation
  We compute analytically the dominant contribution to the tree-level
bispectrum in the Starobinsky model of inflation. In this model, the potential
is vacuum energy dominated but contains a subdominant linear term which changes
the slope abruptly at a point. We show that on large scales compared with the
transition scale $k_0$ and in the equilateral limit the analogue of the
non-linearity parameter scales as $(k/k_0)^2$, that is its amplitude decays for
larger and larger scales until it becomes subdominant with respect to the usual
slow-roll suppressed corrections. On small scales we show that the
non-linearity parameter oscillates with angular frequency given by $3/k_0$ and
its amplitude grows linearly towards smaller scales and can be large depending
on the model parameters. We also compare our results with previous results in
the literature.
