Inflation in Non-de Sitter Background with Coherent States

TL;DR

This paper investigates how excited coherent states over non-de Sitter modes modify primordial scalar fluctuation spectra, revealing tiny initial non-Gaussianities that grow over time and are consistent with observations.

Contribution

It introduces a novel approach using excited coherent states over non-de Sitter modes to analyze primordial fluctuations, extending previous models to non-de Sitter backgrounds.

Findings

Non-zero one-point function in non-interacting Lagrangian.

Primordial non-Gaussianity is tiny initially but grows over time.

Results align with standard models in the de Sitter limit.

Abstract

We use the excited coherent states built over the initial non-de Sitter modes, to study the modification of spectra of primordial scalar fluctuation. Non-de Sitter modes are actually the asymptotic solution of the inflaton field equation[JHEP 09(2014) 020]. We build excited coherent states over the non-de Sitter modes and despite the lack of interactions in the Lagrangian, we find a non-zero one-point function. It is shown that the primordial non-Gaussianity resulting from excited-de Sitter modes depend both of time and background space-time. It is very tiny of order $(\leq{10}^{-24})$, at the Planck initial fixed time that confirmed by resent observations for single field inflation but it grows in the present epoch. Moreover, our results at the leading order are similar to what obtained with general initial states and in the dS limit leads to standard results [JCAP 1202(2012) 005]. We will show that the non-dS modes and its resulting spectrum are more usable for far past time limit.