Pre-inflation from the multiverse: Can it solve the quadrupole problem in the cosmic microwave background?

TL;DR

This paper investigates whether a pre-inflationary phase from a multiverse model can explain the quadrupole anomaly in the CMB, using a quantum cosmological approach, but finds it does not in the specific model studied.

Contribution

It introduces a quantum-field-theoretical third quantization model of eternal inflation to analyze pre-inflationary effects on the CMB power spectrum.

Findings

Pre-inflationary phase does not resolve the quadrupole problem in the specific model.

The model provides a framework to connect multiverse dynamics with observable CMB features.

Potential resolutions of the quadrupole issue are discussed but not confirmed.

Abstract

We analyze a quantized toy model of a universe undergoing eternal inflation using a quantum-field-theoretical formulation of the Wheeler-DeWitt equation. This so-called third quantization method leads to the picture that the eternally inflating universe is converted to a multiverse in which sub-universes are created and exhibit a distinctive phase in their evolution before reaching an asymptotic de Sitter phase. From the perspective of one of these sub-universes, we can thus analyze the pre-inflationary phase that arises naturally. Assuming that our observable universe is represented by one of those sub-universes, we calculate how this pre-inflationary phase influences the power spectrum of the cosmic microwave background (CMB) anisotropies and analyze whether it can explain the observed discrepancy of the power spectrum on large scales, i.e. the quadrupole issue in the CMB. While the answer to this question is negative in the specific model analyzed here, we point out a possible resolution of this issue.