Mirage effects on the brane

TL;DR

This paper explores how matter in the bulk influences brane cosmology, leading to observable mirage effects such as apparent dark matter and curvature, without actual matter on the brane.

Contribution

It introduces a detailed analysis of mirage effects caused by bulk matter, including anisotropic fluids and monopole configurations, affecting brane universe expansion.

Findings

Mirage non-relativistic matter can mimic dark matter effects.

Bulk anisotropic fluids induce deviations in brane expansion.

Bulk monopole configurations can cause a positively curved brane universe to expand forever.

Abstract

We discuss features of the brane cosmological evolution that arise through the presence of matter in the bulk. As these deviations from the conventional evolution are not associated with some observable matter component on the brane, we characterize them as mirage effects. We review an example of expansion that can be attributed to mirage non-relativistic matter (mirage cold dark matter) on the brane. The real source of the evolution is an anisotropic bulk fluid with negative pressure along the extra dimension. We also study the general problem of exchange of real non-relativistic matter between the brane and the bulk, and discuss the related mirage effects. Finally, we derive the brane cosmological evolution within a bulk that contains a global monopole (hedgehog) configuration. This background induces a mirage curvature term in the effective Friedmann equation, which can cause a brane Universe with positive spatial curvature to expand forever.