Is it true that for an isotropic, homogeneous flat universe with dust(adsbygoogle = window.adsbygoogle || []).push({});

and a positive cosmological constant, the universe necessarily expands

forever? The argument may be,

(a_t/a)^2 = (8*pi*G/3)*rho + lambda/3 (Friedmann equation)

where a_t refers to the first derivative of a with respect to t. Now

the right hand side is strictly positive (as rho is positive and

proportional to a^3 for dust), so a_t is always positive.

If this is true, why is it said that in a universe with a positive

cosmological constant, the fate of the universe has no direct relation

with the curvature (k) but depends on the exact proportion of

[(matter+radiation) density] / vacuum energy density?

**Physics Forums - The Fusion of Science and Community**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Cosmology Question - Please Help

Loading...

Similar Threads - Cosmology Question Please | Date |
---|---|

B What do I need to become an Astrophysicist? | Feb 25, 2018 |

I Black Holes and Dark Energy | Feb 21, 2018 |

I Question about the cosmological constant | Apr 11, 2016 |

3 questions on Physical Cosmology | Sep 3, 2008 |

An ignorant question about cosmology | Mar 12, 2004 |

**Physics Forums - The Fusion of Science and Community**