Re: cosmological constant

From: alistair (alistair_at_goforit64.fsnet.co.uk)
Date: 06/27/04 

Date: Sun, 27 Jun 2004 23:02:34 +0000 (UTC)

rwmw@telus.net (Rob Woodside) wrote in message news:<4d06b9d7.0406231715.dd9750b@posting.google.com>...
 
> The most general symmetric, divergence free, second rank geometric
> tensor is then G + Lg. This should then couple to T with the constant
> k to give Einstein's equations: G + Lg = kT
>
> Notice that the Cosmological constant L is giving the relative
> weighting of metric to curvature that is required by T. Curvature and
> metric are apples and oranges, but this Blunder with positive L
> allowed Einstein a non collapsing universe. Hubble's dynamic universe
> had no need for the constraining L
>
> Now we are forced to accept a universe with accelerating expansion. A
> quick fix is to postulate a new type of matter called dark energy with
> a stress-energy tensor Td, satisfying kTd = -Lg. The total stress
> energy tensor is now T'=T+Td and Einstein's equations become G=kT'.
> Dark energy is very bizarre with a negative energy density that is
> minus the isotropic pressure. It is divergence free so nothing can
> push on it. I doubt that this will be the ultimate explanation of the
> accelerating expansion, but it is a place to start and may stimulate
> some experiments that will get us thinking on the right track.

ALISTAIR writes:

T changes slowly with time as the space dimensions of the universe
expand (for example the energy density of a large mass reduces).
Td does not change with time because more dark energy is created as
the space dimensions expand.Over a short period of time it is
correct to write T'= T + Td but is it okay to do this in the long run?

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