Standard cosmology on the Anti-de Sitter boundary

Abstract

The well-known brane world model of cosmology is an alternative to the standard model of cosmology, called Lambda Cold Dark Matter (ΛCDM) model. However, the quadratical energy density of the brane universe requires an undesirable fine tuning. The paper develops a new Anti-de Sitter (AdS) brane world model without the quadratical energy density by using a second Einstein equation, which arises canonically during a holographic renormalisation. On the AdS boundary it is demonstrated that this brane model equals an effective de Sitter ΛCDM model, whereas the brane model near the AdS boundary agrees to the ΛCDM model except the earliest times. Finally, it is shown that the coincidence problem is avoided and the cosmological constant problem, if not solved, is greatly reduced.