Quantum cosmological background superposition and perturbation predictions

TL;DR

This paper explores how allowing a highly non-classical quantum background in early universe cosmology can lead to significantly different predictions for primordial perturbations, challenging the classical assumptions typically made.

Contribution

It introduces a novel approach to quantum cosmology by defining quantum trajectories for a non-classical background while maintaining the Born-Oppenheimer factorization.

Findings

Background trajectories become nearly classical asymptotically.

Perturbation power spectrum predictions can differ substantially from classical models.

The approach provides new insights into quantum effects in early universe cosmology.

Abstract

Predictions from early universe cosmology typically concern primordial perturbations generated during epochs where effects arising from the quantum nature of gravity may be important; quantum vacuum fluctuations being stretched to cosmological scales during a phase of inflation. Quantizing the background is then done by assuming a single close-to-classical state over which perturbations grow, as well as a Born-Oppenheimer factorization throughout the relevant phase. We present a scenario in which although the latter factorization remains valid at all times, we allow the background state to be very non-classical by defining quantum trajectories through an eikonal approximation. We find that these trajectories asymptotically reproduce an almost classical behavior for the background, but the predictions for the power spectrum of perturbations can significantly differ.