The structure of singularities in inhomogeneous cosmological models

TL;DR

This paper reviews recent advances in understanding the structure of cosmological singularities, focusing on the BKL picture, its validity, and cases with simpler singularities that are more accessible to mathematical analysis.

Contribution

It summarizes current analytical and numerical results on cosmological singularities and discusses the validity of the BKL description in inhomogeneous models.

Findings

Most singularities are complex according to BKL

Some cases exhibit simple singularities

Progress has been made in mathematical investigations of these cases

Abstract

Recent progress in understanding the structure of cosmological singularities is reviewed. The well-known picture due to Belinskii, Khalatnikov and Lifschitz (BKL) is summarized briefly and it is discussed what existing analytical and numerical results have to tell us about the validity of this picture. If the BKL description is correct then most cosmological singularities are complicated. However there are some cases where it predicts simple singularities. These cases should be particularly amenable to mathematical investigation and the results in this direction which have been achieved so far are described.