## Abstract

We analyze cosmological equations in the brane world scenario with one extra space-like dimension. We demonstrate that the cosmological equations can be reduced to the usual 4D Friedmann type if the bulk energy-momentum tensor is different from zero. We then generalize these equations to the case of a brane of finite thickness. We also demonstrate that when the bulk energy-momentum tensor is different from zero, the extra space-like dimension can be compactified with a single brane and show that the stability of the radius of compactification implies standard cosmology and vice versa. For a brane of finite thickness, we provide a solution such that the 4D Planck scale is related to the fundamental scale by the thickness of the brane. In this case, compactification of the extra dimension is unnecessary.

Original language | English (US) |
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Pages (from-to) | 31-39 |

Number of pages | 9 |

Journal | Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics |

Volume | 468 |

Issue number | 1-2 |

DOIs | |

State | Published - 1999 |

### Bibliographical note

Funding Information:This work was supported in part by the Department of Energy under Grant No. DE-FG-02-94-ER-40823 at the University of Minnesota, and PPARC grant GR/L56565 and INTAS 95-RFBR-567 at Oxford. One of us (I.K.) wants to thank TPI and Department of Physics, University of Minnesota for its hospitality during the summer of 1999 where this work began.