Speaker
Description
The presence of multiple massive scalar fields during inflation is often a generic prediction of UV complete theories of gravity. In addition to the top down motivation, multifield models of inflation also solve the “$\eta$-problem” by incorporating non-geodesic trajectories in the field space. Deviations of the inflaton’s trajectory from the geodesic, quantified by bending parameters, generate sizable non-Gaussianities beyond just the single-field slow roll scenario. While two field models with “turning” have been well studied, models with more than two active fields remain unexplored. In this work we take a phenomenological approach to study the non-Gaussianities that are generated by having more than two active fields during inflation. In particular we obtain the squeezed limit bispectrum of the adiabatic modes, which in presence of coupling to multiple massive fields, produces the so called “cosmological collider signal”. While our results hold for the general $N>2$ field case, for pedagogy we highlight these results in the special case of $N=3$ fields that has two bending parameters - “torsion” and “turning”. Upon carefully considering all the cubic vertices we find that the squeezed limit bispectrum has mixed oscillations for multiple heavy fields that depend on the mass gap. We also find that for some vertices that are unique to having $N>2$ fields, there’s a novel shape that generates a large local contribution in the squeezed limit. These findings could help discern different multifield models via specific template searches in cosmological data.
| Other topic / keywords: | cosmological collider, non-Gaussianities |
|---|