Prospects for constraining the shape of non-Gaussianity with the scale-dependent bias

TL;DR

This paper investigates whether the scale-dependent halo bias can differentiate among various shapes of primordial non-Gaussianity, especially in the squeezed limit, to shed light on inflationary dynamics.

Contribution

It demonstrates that large-scale structure surveys can potentially distinguish between different bispectrum shapes in the squeezed limit, aiding in constraining inflation models.

Findings

Surveys can differentiate bispectrum shapes in the squeezed limit.

Halo bias can discriminate between inflationary models.

Model-independent parametrization is effective for analysis.

Abstract

We consider whether the non-Gaussian scale-dependent halo bias can be used not only to constrain the local form of non-Gaussianity but also to distinguish among different shapes. In particular, we ask whether it can constrain the behavior of the primordial three-point function in the squeezed limit where one of the momenta is much smaller than the other two. This is potentially interesting since the observation of a three-point function with a squeezed limit that does not go like the local nor equilateral templates would be a signal of non-trivial dynamics during inflation. To this end we use the quasi-single field inflation model of Chen and Wang as a representative two-parameter model, where one parameter governs the amplitude of non-Gaussianity and the other the shape. We also perform a model-independent analysis by parametrizing the scale-dependent bias as a power-law on large scales, where the power is to be constrained from observations. We find that proposed large-scale structure surveys (with characteristics similar to the dark energy task force stage IV surveys) have the potential to distinguish among the squeezed limit behavior of different bispectrum shapes for a wide range of fiducial model parameters. Thus the halo bias can help discriminate between different models of inflation.