Inflation with General Initial Conditions for Scalar Perturbations

TL;DR

This paper investigates how general initial conditions for scalar perturbations in inflation affect observable spectra, finding many states consistent with current data but constrained by renormalizability.

Contribution

It computes the power spectrum and bispectrum for a broad class of initial states, showing many are observationally indistinguishable from the standard vacuum.

Findings

Many initial states are consistent with current observations.

Constraints from renormalizability further restrict initial states.

Large class of initial states produce spectra similar to Bunch-Davies vacuum.

Abstract

We explore the possibility of a single field quasi-de Sitter inflationary model with general initial state for primordial fluctuations. In this paper, first we compute the power spectrum and the bispectrum of scalar perturbations with coherent state as the initial state. We find that a large class of coherent states are indistinguishable from the Bunch-Davies vacuum state and hence consistent with the current observations. In case of a more general initial state built over Bunch-Davies vacuum state, we show that the constraints on the initial state from observed power spectrum and local bispectrum are relatively weak and for quasi-de Sitter inflation a large number of initial states are consistent with the current observations. However, renormalizability of the energy-momentum tensor of the fluctuations constraints the initial state further.