Brane World Cosmology

TL;DR

This paper reviews the cosmological implications of brane world models, including the Randall--Sundrum scenario and two-brane systems, discussing their effective theories, perturbations, and observable consequences.

Contribution

It provides a comprehensive overview of brane world cosmology, comparing different methods to derive low-energy theories and exploring their physical implications.

Findings

Effective theories for two-brane systems are compared.

Cosmological perturbations in brane models are discussed.

Impacts on cosmic microwave background and constants variation are analyzed.

Abstract

Recent developments in the physics of extra dimensions have opened up new avenues to test such theories. We review cosmological aspects of brane world scenarios such as the Randall--Sundrum brane model and two--brane systems with a bulk scalar field. We start with the simplest brane world scenario leading to a consistent cosmology: a brane embedded in an Anti--de Sitter space--time. We generalise this setting to the case with a bulk scalar field and then to two--brane systems. We discuss different ways of obtaining a low--energy effective theory for two--brane systems, such as the moduli space approximation and the low--energy expansion. A comparison between the different methods is given. Cosmological perturbations are briefly discussed as well as early universe scenarios such as the cyclic model and the born--again brane world model. Finally we also present some physical consequences of brane world scenarios on the cosmic microwave background and the variation of constants.