Hi there,(adsbygoogle = window.adsbygoogle || []).push({});

I really hope someone can help me with my stupid but urgent problem of understanding something crucial about the Friedman equations.

So; one of them looks like this (forget about the constants; it is about the principles):

change of the scale factor with time - density - cosmol. constant = -k (curvature term)

Then this is sometimes rewritten in terms of densities, which gives:

change of the scale factor with time - (density of matter + vacuum energy density) = -k (curvature term)

Now; here is what I do not get.

Generally the density of the vacuum (or equivalently the cosmol. constant) are treated just like the density of matter; so they have the same effect on the curvature, which somehow should be understandable as energy=matter and so both curve the spacetime.

But then, it is usually stated that the cosmol. constant, and so the vacuum energy density, are working against gravitation (repulsive).

However; I do not understand, how to see this in the equations above. I mean; both seem to have the same effect: energy=matter -> attraction (simplified).

Where is my error of thinking?

I really hope that someone here can enlighten me.

Thx

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# Help with Friedman equations and density of energy

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