Large and strong scale dependent bispectrum in single field inflation
  from a sharp feature in the mass
  We study an inflationary model driven by a single minimally coupled standard
kinetic term scalar field with a step in its mass modeled by an Heaviside step
function. We present an analytical approximation for the mode function of the
curvature perturbation, obtain the power spectrum analytically and compare it
with the numerical result. We show that, after the scale set by the step, the
spectrum contains damped oscillations that are well described by our analytical
approximation. We also compute the dominant contribution to the bispectrum in
the equilateral and the squeezed limits and find new shapes. In the equilateral
and squeezed limits the bispectrum oscillates and it has a linear growth
envelope towards smaller scales. The bispectrum size can be large depending on
the model parameters.
