I am studying general relativity from Hobson and came across the term 'lifetime' of a closed (k>0) universe, ##t_{lifetime}##.(adsbygoogle = window.adsbygoogle || []).push({});

I suppose at late times the curvature dominates and universe starts contracting? Are they simply referring to ##\int_0^{\infty} dt##? If so, would the bottom expression be right?

[tex]\int_0^{\infty}dt = \int_1^{0} \frac{1}{a(t) H(t)} dt[/tex]

Do you think this makes sense since ##a(t)## is decreasing and will eventually reach ##0##?

Then for an open universe (k<0), wont the universe simply keep expanding? If I read right, our universe is mostly flat, right? Then what is driving the expansion? Dust?

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# Lifetime of the universe - what are the limits?

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