What can quantum cosmology say about the inflationary universe?

TL;DR

This paper develops a method using quantum cosmology to predict initial conditions for inflation, linking quantum predictions with observational data like primordial gravitational waves, and constrains inflation models.

Contribution

It introduces a novel approach to derive inflation initial conditions from quantum geometrodynamics and applies it to specific inflation models for observational consistency.

Findings

Identifies a peaked probability distribution for the inflaton field.

Provides constraints on inflation model parameters based on quantum cosmology.

Demonstrates the method with Higgs and natural inflation models.

Abstract

We propose a method to extract predictions from quantum cosmology for inflation that can be confronted with observations. Employing the tunneling boundary condition in quantum geometrodynamics, we derive a probability distribution for the inflaton field. A sharp peak in this distribution can be interpreted as setting the initial conditions for the subsequent phase of inflation. In this way, the peak sets the energy scale at which the inflationary phase has started. This energy scale must be consistent with the energy scale found from the inflationary potential and with the scale found from a potential observation of primordial gravitational waves. Demanding a consistent history of the universe from its quantum origin to its present state, which includes decoherence, we derive a condition that allows one to constrain the parameter space of the underlying model of inflation. We demonstrate our method by applying it to two models: Higgs inflation and natural inflation.