Localized Features in Non-Gaussianity from Heavy Physics

TL;DR

This paper explores how localized features in the primordial bispectrum caused by heavy physics during inflation can reveal signatures of heavy fields, with potential large amplitude signals in specific configurations.

Contribution

It demonstrates that resonance effects from heavy fields produce localized, amplified features in the bispectrum, providing a new way to probe heavy physics during inflation.

Findings

Resonance can amplify the bispectrum by factors up to 10^5.

Features are localized in momentum space and prominent in finitely squeezed configurations.

The bispectrum features can be much larger than those in the power spectrum, indicating heavy physics presence.

Abstract

We discuss the possibility that we could obtain some hints of the heavy physics during inflation by analyzing local features of the primordial bispectrum. A heavy scalar field could leave large signatures in the primordial spectra through the parametric resonance between its background oscillation and the fluctuations. Since the duration of the heavy-mode oscillations is finite, the effect of the resonance is localized in momentum space. In this paper, we show that the bispectrum is amplified when such a resonance occurs, and that the peak amplitude of the feature can be O(10^{1-2}), or as large as O(10^5) depending on the type of interactions. In particular, the resonance can give large contributions in finitely squeezed configurations, while the bispectrum cannot be large in the exact squeezed limit. We also find that there is a relation between the scales at which the features appear in the bispectrum and the power spectrum, and that the feature in the bispectrum can be much larger than that in the power spectrum. If correlated features are observed at characteristic scales in the primordial spectra, it will indicate the presence of heavy degrees of freedom. By analyzing these features, we may be able to obtain some information on the physics behind inflation.