On the emergence of a classical Isotropic Universe from a Quantum $f(R)$ Bianchi Cosmology in the Jordan Frame

TL;DR

The paper investigates how quantum wave packets in a modified $f(R)$ Bianchi cosmology tend to become classical, but this classicality is unstable without inflation, whereas a perturbative inflationary scenario can stabilize the classical behavior.

Contribution

It demonstrates a mechanism for stable classicalization of the Universe in a modified $f(R)$ cosmology, contrasting with standard relativistic cosmology.

Findings

Quantum wave packets tend to become quasi-classical initially.

Classicalization is unstable after a critical relational time without inflation.

Perturbative inflation stabilizes the classical behavior in the isotropic Universe.

Abstract

We demonstrate a spontaneous tendency of quantum wave packets to become quasi-classical, providing a classical limit for the Universe dynamics. However, this limit is not maintained in the future (after a critical value of the relational time) and a spreading process is turned on. We show that the onset of an inflationary scenario is not able to make this localization stable of the wave packets for the Bianchi I model. Instead, when we implement a perturbative inflationary scenario for the isotropic Universe a mechanism of stable classicalization of the Universe emerges. This result outlines a sharp difference between the standard relativistic cosmology and a modified $f(R)$ paradigm.