Billiard Representation for Multidimensional Cosmology with Multicomponent Perfect Fluid near the Singularity

TL;DR

This paper models the near-singularity behavior of multidimensional cosmology with multicomponent fluids as a billiard problem in hyperbolic space, providing criteria for the billiard's volume and exploring generalizations including scalar fields and quantum effects.

Contribution

It introduces a geometrical billiard representation for multidimensional cosmology near singularities, linking the dynamics to illumination problems on spheres and extending to scalar and quantum cases.

Findings

Billiard dynamics describe the approach to singularity in the model.

A criterion for billiard volume finiteness and compactness is proposed.

Generalizations include scalar fields and quantum effects.

Abstract

The multidimensional cosmological model describing the evolution of $n$ Einstein spaces in the presence of multicomponent perfect fluid is considered. When certain restrictions on the parameters of the model are imposed, the dynamics of the model near the singularity is reduced to a billiard on the $(n-1)$-dimensional Lobachevsky space $H^{n-1}$. The geometrical criterion for the finiteness of the billiard volume and its compactness is suggested. This criterion reduces the problem to the problem of illumination of $(n-2)$-dimensional sphere $S^{n-2}$ by point-like sources. Some generalization of the considered scheme (including scalar field and quantum generalizations) are considered.