In the lambda-CDM model, the Universe is spatially flat, and will expand forever. Is possible that a spatially closed Universe expands forever?
1 Answer
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Yes, if the Universe is matter-dominated and spatially closed, then a cosmological constant:
$\Lambda > \frac{4\pi G \rho}{c^2}$
Where $\rho$ is the critical energy density (of matter) of the Universe, will cause it to expand forever.
NB Where $\Lambda$ is equal to this value you get the (unstable) Einstein static Universe.