The bispectrum in the Effective Field Theory of Large Scale Structure

Abstract

We study the bispectrum in the Effective Field Theory of Large Scale\nStructure, consistently accounting for the effects of short-scale dynamics. We\nbegin by proving that, as long as the theory is perturbative, it can be\nformulated to arbitrary order using only operators that are local in time. We\nthen derive all the new operators required to cancel the UV-divergences and\nobtain a physically meaningful prediction for the one-loop bispectrum. In\naddition to new, subleading stochastic noises and the viscosity term needed for\nthe one-loop power spectrum, we find three new effective operators. The three\nnew parameters can be constrained by comparing with N-body simulations. The\nbest fit is precisely what is suggested by the structure of UV-divergences,\nhence justifying a formula for the EFTofLSS bispectrum whose only fitting\nparameter is already fixed by the power spectrum. This result predicts the\nbispectrum of N-body simulations up to $k \\approx 0.22\\, h\\, \\text{Mpc}^{-1}$\nat $z=0$, an improvement by nearly a factor of two as compared to one-loop\nstandard perturbation theory.\n