  We extend the formalism of time-sliced perturbation theory (TSPT) for
cosmological large-scale structure to include non-Gaussian initial conditions.
We show that in such a case the TSPT interaction vertices acquire new
contributions whose time-dependence factorizes for the Einstein-de Sitter
cosmology. The new formulation is free from spurious infrared (IR) enhancements
and reveals a clear IR structure of non-Gaussian vertices. We use the new
technique to study the evolution of oscillating features in primordial
statistics and show that they are damped due to non-linear effects of large
bulk flows. We derive the damping factors for the oscillating primordial power
spectrum and bispectrum by means of a systematic IR resummation of relevant
Feynman diagrams.
