Appearance of classical Mixmaster Universe from the No-Boundary Quantum State

TL;DR

This paper explores how classical anisotropic universes can emerge from the no-boundary quantum state, showing that anisotropic histories are less probable but can lead to inflation, with some histories becoming singular when extended backward.

Contribution

It demonstrates the emergence of classical anisotropic universes from the no-boundary quantum state within a specific cosmological model, highlighting the probability distribution of anisotropies.

Findings

An ensemble of anisotropic histories experience late-time inflation.

Histories with anisotropies are less probable than isotropic ones.

Some histories become singular when extended back in time.

Abstract

We investigate the appearance of the classical anisotropic universe from the no-boundary quantum state according to the prescription proposed by Hartle, Hawking and Hertog. Our model is homogeneous, anisotropic, closed universes with a minimally coupled scalar field and cosmological constant. We found that there are an ensemble of classical Lorentzian histories with anisotropies and experience inflationary expansion at late time, and the probability of histories with anisotropies are lower than isotropic histories. Thus the no-boundary condition may be able to explain the emergence of our universe. If the classical late time histories are extended back, some become singular by the existence of initial anisotropies with large accelerations. However we do not find any chaotic behavior of anisotropies near the initial singularity.