The effect of local non-Gaussianity on the matter bispectrum at small scales

We compute the matter bispectrum in the presence of primordial local non-Gaussianity over a wide range of scales, including the very small nonlinear ones. We use the Halo Model approach, considering non-Gaussian corrections to the halo proles, the halo mass function and the bias functions. We compare our results in the linear and mildly nonlinear scales to a large ensemble of Gaussian and non-Gaussian numerical simulations. We consider both squeezed and equilateral congurations, at redshift z = 0 and z = 1. For z = 0, the deviations between the Halo Model and the simulations are smaller than 10% in the squeezed limit, both in the Gaussian and non-Gaussian cases. The Halo Model allows to make predictions on scales much smaller than those reached by numerical simulations. For local non-Gaussian initial conditions with a parameter f_NL = 100, we find an enhancement of the bispectrum in the squeezed conguration k = k₃ = k₂ >> k₁ ~ 0.011 Mpc/h, of about 15% and about 25% on scales k ~ 1 Mpc/h, at z = 0 and z = 1 respectively. This is mainly due to the non-Gaussian corrections in the linear bias. Finally we provide a very simple expression valid for any scenario, i.e. for any choice of the halo prole, mass and bias functions, which allow for a fast evaluation of the bispectrum on squeezed congurations.