BKL maps and Poincar\'e sections

TL;DR

This paper explores cosmological billiards near singularities, analyzing BKL maps and Poincaré sections in 4D gravity, and investigates the quantum behavior, revealing the likelihood of certain BKL eras and wavefunction characteristics.

Contribution

It introduces a 3D phase space framework for BKL maps in pure gravity and examines the quantum regime, linking statistical properties with semiclassical wavefunctions.

Findings

1-epoch BKL eras are most probable for wavefunctions.

BKL eras with many epochs are less probable.

Wavefunction 'scars' are observed in semiclassical analysis.

Abstract

Cosmological billiards arise as a map of the solution to the Einstein equations, when the most general symmetry of the metric tensor is implemented, under the BKL (named after Belinskii, Khalatnikov and Lifshitz) paradigm, for which points are spatially decoupled in the asymptotical limit close to the cosmological singularity. Cosmological billiards in $4=3+1$ dimensions for the case of pure gravity are analyzed for those features, for which the content of Weyl reflections in the BKL maps requires definition of a 3-dimensional restricted phase space. The role of Poincar\'e sections in these processes is outlined. The quantum regime is investigated within this framework: as a result, 1-epoch BKL eras are found to be the most probable configuration at which the wavefunctions have to be evaluated; furthermore, BKL eras containing $n>>1$ epochs are shown to be a less probable configuration for the wavefunctions. This description of the dynamics allows one to gain information about the connections between the statistical characterization of the maps which imply the different symmetry-quotienting mechanisms and the characterization of the semiclassical limit of the wavefunctions for the classical trajectories, for which the phenomenon of 'scars' on the wavefunction is found for other kinds of billiards.