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Unformatted text preview: arXiv:hepth/0404011v1 2 Apr 2004 Brane World Cosmology Philippe Brax , Carsten van de Bruck and AnneChristine Davis Service de Physique Th eorique, CEASaclay F91191, Gif/Yvette cedex, France Department of Applied Mathematics, AstroParticle and Cosmology Group University of Sheffield, Hounsfield Road, Hicks Building Sheffield S3 7RH, United Kingdom * Department of Applied Mathematics and Theoretical Physics, Center for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, U.K. Email: brax@spht.saclay.cea.fr, C.vandeBruck@sheffield.ac.uk, acd@damtp.cam.ac.uk 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 RandallSundrum brane model and twobrane systems with a bulk scalar field. We start with the simplest brane world scenario leading to a consistent cosmology: a brane embedded in an Antide Sitter spacetime. We generalise this setting to the case with a bulk scalar field and then to twobrane systems. We discuss different ways of obtaining a lowenergy effective theory for twobrane systems, such as the moduli space approximation and the lowenergy 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 bornagain brane world model. Finally we also present some physical consequences of brane world scenarios on the cosmic microwave background and the variation of constants. Brane World Cosmology 2 1. Introduction Whilst theories formulated in extra dimensions have been around since the early twentieth century, recent developments have opened up new avenues which have enabled the cosmological consequences of such theories to be extracted. This, together with advances in high precision cosmological data, opens up the exciting possibility of testing and constraining extradimensional theories for the first time. In this review we explore these developments. In the early twentieth century Kaluza and Klein [1], following Nordstrom, attempted to unify electromagnetism and gravity by proposing a theory in five spacetime dimensions, with the extra spatial dimension compactified on a circle. More recently, attempts to construct a consistent theory incorporating both quantum mechanics and gravity have been constructed in more than four dimensions, with the extra, spatial dimensions compactified. In particular superstring theories, which include both quantum theory and gravity, are only consistent in ten dimensions [2], with the extra dimensions being spatial. The usual four dimensional physics is retrieved by compactifying on a compact manifold with dimensions typically of the order of the Planck scale. This is essentially a generalisation of KaluzaKlein theory....
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This note was uploaded on 04/16/2008 for the course PHYS 101 taught by Professor Ballz during the Spring '08 term at IUP.
 Spring '08
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