Interpretation of the triad orientations in loop quantum cosmology

TL;DR

This paper demonstrates how fermion interactions cause decoherence in loop quantum cosmology, leading to classical triad orientations from quantum superpositions, thus explaining the emergence of definite universe orientations.

Contribution

It shows how fermion-induced decoherence makes quantum superpositions of triad orientations appear as classical mixtures in loop quantum cosmology.

Findings

Decoherence reduces the purity of triad superpositions.

Fermion interactions cause the universe to assume a definite orientation.

Reduced density matrix analysis confirms classical behavior emergence.

Abstract

Loop quantum cosmology allows for arbitrary superpositions of the triad variable. We show here how these superpositions can become indistinguishable from a classical mixture by the interaction with fermions. We calculate the reduced density matrix for a locally rotationally symmetric Bianchi I model and show that the purity factor for the triads decreases by decoherence. In this way, the universe assumes a definite orientation.