Signatures of very high energy physics in the squeezed limit of the bispectrum

Abstract

We investigate the signatures in the squeezedlimit of the primordial scalar bispectrum due tomodifications of the standard theory at high energy. In particular, weconsider the cases of modified dispersion relations and/or modified initialquantum state (both in the Boundary Effective Field Theory and in theNew Physics Hyper-Surface formulations). Using the in-in formalism we study in detailsthe squeezed limit of the contributions to the bispectrum from allpossible cubic couplings in the effective theory of single-field inflation.We find general features such as enhancements and/or non-local shape of the non-Gaussianities, which are relevant, for example, formeasurements of the halo bias and which distinguish these scenarios from thestandard one (with Bunch-Davies vacuum as initial state and standardkinetic terms). We find that the signatures change according to the magnitude of the scale of new physics, and therefore severalpieces of information regarding high energy physics could be obtainedin case of detection of these signals, especially bounds on the scales of new physics.