Towards the physical vacuum of cosmic inflation

TL;DR

This paper demonstrates how interactions during cosmic inflation cause the decay of excited initial states, with implications for understanding the early universe and probing trans-Planckian physics through non-Gaussianity.

Contribution

It explicitly shows the decay of non-Bunch-Davies initial states during inflation via one-loop interactions, linking non-Gaussianity to initial condition decay.

Findings

Decay of excited states during inflation confirmed

Folded shape non-Gaussianity interpreted as decay signature

Small observed non-Gaussianity allows probing initial conditions

Abstract

There have been long debates about the initial condition of inflationary perturbations. In this work we explicitly show the decay of excited states during inflation via interactions. For this purpose, we note that the folded shape non-Gaussianity can be interpreted as the decay of the non-Bunch-Davies initial condition. The one loop diagrams with non-Bunch-Davies propagators are calculated to uncover the decay of such excited states. The observed smallness of non-Gaussianity keeps the window open for probing inflationary initial conditions and trans-Planckian physics.