Effects and Detectability of Quasi-Single Field Inflation in the Large-Scale Structure and Cosmic Microwave Background

TL;DR

This paper investigates how quasi-single field inflation influences large-scale structure and CMB observations, focusing on the bispectrum's momentum dependence and its detectability with upcoming data.

Contribution

It analyzes the effects of quasi-single field inflation on observable non-Gaussian features and assesses the potential to distinguish it from other models using future large-scale structure and CMB data.

Findings

Galaxy power spectrum can differentiate QSF from local models for large non-Gaussianity.

Planck data may distinguish QSF models from local and equilateral shapes within certain parameter ranges.

Joint analysis of CMB and LSS reduces degeneracies and improves model constraints.

Abstract

Quasi-single field inflation predicts a peculiar momentum dependence in the squeezed limit of the primordial bispectrum which smoothly interpolates between the local and equilateral models. This dependence is directly related to the mass of the isocurvatons in the theory which is determined by the supersymmetry. Therefore, in the event of detection of a non-zero primordial bispectrum, additional constraints on the parameter controlling the momentum-dependence in the squeezed limit becomes an important question. We explore the effects of these non-Gaussian initial conditions on large-scale structure and the cosmic microwave background, with particular attention to the galaxy power spectrum at large scales and scale-dependence corrections to galaxy bias. We determine the simultaneous constraints on the two parameters describing the QSF bispectrum that we can expect from upcoming large-scale structure and cosmic microwave background observations. We find that for relatively large values of the non-Gaussian amplitude parameters, but still well within current uncertainties, galaxy power spectrum measurements will be able to distinguish the QSF scenario from the predictions of the local model. A CMB likelihood analysis, as well as Fisher matrix analysis, shows that there is also a range of parameter values for which Planck data may be able distinguish between QSF models and the related local and equilateral shapes. Given the different observational weightings of the CMB and LSS results, degeneracies can be significantly reduced in a joint analysis.