Mirage Cosmology

TL;DR

Mirage cosmology proposes that our four‑dimensional universe is a probe D3‑brane moving through a curved ten‑dimensional bulk. Using the DBI action, the authors show that brane motion induces a Friedmann‑like expansion on the brane, with a mirage energy density sourced by bulk fields, brane angular momentum, and world‑volume fields. They analyze several bulk backgrounds (AdS black holes, black branes, constant B‑fields, and electric fields) and reveal a spectrum of effective equations of state, including exotic w values and negative densities, and discuss how the initial singularity can be resolved in the higher‑dimensional setting. The work also sketches how to embed this picture into string theory via orientifold/orbifold vacua and highlights future directions for realizing inflation, dust‑like mirage matter, and curvature within this framework.

Abstract

A brane universe moving in a curved higher dimensional bulk space is considered. The motion induces a cosmological evolution on the universe brane that is indistiguishable from a similar one induced by matter density on the brane. The phenomenological implications of such an idea are discussed. Various mirage energy densities are found, corresponding to dilute matter driving the cosmological expansion, many having superluminal properties $|w|>1$ or violating the positive energy condition. It is shown that energy density due to the world-volume fields is nicely incorporated into the picture. It is also pointed out that the initial singularity problem is naturally resolved in this context.