- Einstein–de Sitter model ():
- Open model with vanishing cosmological constant ():
- Spatially-flat model with cosmological constant ():

In the above, denotes the present age of the Universe,

and we adopt the initial condition that at . The expression clearly indicates that increases as decreases and/or increases. Figure 1 plots the scale factor as a function of , and Table 1 summarizes the age of the Universe.Open model | Spatially-flat model | |

() | () | |

1.0 | 9.3 | 9.3 |

0.5 | 10.5 | 11.6 |

0.3 | 11.3 | 13.5 |

0.1 | 12.5 | 17.8 |

0.01 | 13.9 | 28.0 |

http://www.livingreviews.org/lrr-2004-8 |
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