Null Geodesics in Brane World Universe

TL;DR

This paper investigates null geodesic motion in brane world cosmology and static bulk universes, revealing additional forces affecting geodesics depending on symmetry conditions and bulk configurations.

Contribution

It derives equations for null geodesics in brane world scenarios and identifies conditions under which extra forces influence geodesic motion.

Findings

Null geodesics are affected by extra non-gravitational forces in brane cosmology.

Extra forces are present even with Z_2 symmetry in static AdS black hole bulk.

The study provides equations describing geodesic motion in these higher-dimensional models.

Abstract

We study null bulk geodesic motion in the brane world cosmology in the RS2 scenario and in the static universe in the bulk of the charged topological AdS black hole. We obtain equations describing the null bulk geodesic motion as observed in one lower dimensions. We find that the null geodesic motion in the bulk of the brane world cosmology in the RS2 scenario is observed to be under the additional influence of extra non-gravitational force by the observer on the three-brane, if the brane universe does not possess the Z_2 symmetry. As for the null geodesic motion in the static universe in the bulk of the charged AdS black hole, the extra force is realized even when the brane universe has the Z_2 symmetry.