A novel pre-inflationary model in view of the lack of angular correlation of CMB

TL;DR

This paper introduces a unified cosmological model linking pre-inflationary and inflationary epochs, explaining large-scale CMB anomalies through a modified early universe dynamics that naturally suppresses large-angle correlations.

Contribution

It presents a novel scalar-field based model that connects pre-inflationary decelerated expansion with inflation, accounting for CMB large-scale anomalies within a consistent framework.

Findings

The model predicts a suppressed primordial power spectrum at large scales.

The vacuum state is well-defined only for sub-horizon modes at inflation onset.

The resulting spectrum aligns with observational constraints and standard inflation in certain limits.

Abstract

In this paper we propose a novel unified cosmological model that connects a pre-inflationary epoch, starting at the Planckian time, with the onset of inflation within a single scalar-field framework. The pre-inflationary phase is characterized by a decelerated expansion with an increasing comoving Hubble horizon, followed by a gradually transition to an accelerated inflationary regime. This early dynamics leads to a modified causal structure that naturally accounts for the suppression of large-angle $(\theta \gtrsim 60^\circ)$ correlations in the cosmic microwave background (CMB) reported by the satellite PLANCK. We study the quantum fluctuations of the scalar field using the Mukhanov-Sasaki formalism and a canonical quantization procedure based on energy minimization. We find that the vacuum state is well-defined only for sub-horizon modes at the onset of inflation, which induces a natural cutoff in the primordial power spectrum. The resulting spectrum exhibits a suppression at large scales while remaining nearly scale-invariant at small scales. In the appropriate limit, the model recovers the standard de Sitter result, in agreement with current observational constraints. These results highlight the relevance of pre-inflationary dynamics for addressing large-scale anomalies within a consistent inflationary framework.