I just wanted to make sure whether I've understood something correctly(adsbygoogle = window.adsbygoogle || []).push({});

In the FRW equation:

[itex](\frac{ \dot a}{a})^2 = \frac{8 \pi G}{3} \rho - \frac{k}{a^2}[/itex]

...there is this curvature term. I'm confused about the meaning of this k. Sometimes they say it can ONLY be -1 , 0 or +1. Sometimes they say it's smaller, bigger or equal zero. So can it or can it not be fractional? If it can - what does it mean?

My understanding so far is, that this whole term is the Gaussian curvature:

[itex] \pm \frac{1}{a^2} [/itex]

Where a is the radius of curvature - and it changes with time as the universe expands;

And so k is there just to provide an appropriate sign for the three cases: flat, spherical or hyperbolic geometry.

Am I right, or can it be fractional?

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# The meaning of the curvature term

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