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*From*: David Bowman <David_Bowman@GEORGETOWNCOLLEGE.EDU>*Date*: Wed, 14 Feb 2001 17:26:45 -0500

Regarding Bob Zannelli's comments:

... Let me postulate a Universe empty of any

mass that is spatially flat. I believe this is a formulation known as the De

Sitter Universe. General Relativity implies the following equation.

((da/dt)^2)*(1/((a^2)*(c^2))+k/(a^2)-A=8*pi*G*p/(3*(c^4))

Where a is the scale factor, k is curvature, A is the cosmological constant

and p is mass-energy density. In a Universe that is spatially flat (K=0) and

has zero energy density (p=0) by solving the above equation we get the

following result:

a=ki*exp((A^.5)*c*t Where Ki is an arbitrary constant.

which suggest under the condition of a spatially flat Universe with zero mass

energy density we end up with an expodential expansion of the scale factor.

This looks a lot like inflation though this approach is really an

oversimplified example.

This is completely correct. I alluded to it in my last post (in a part

that you didn't quote) where I discussed what happens to an expanding

universe that is spatially flat (& homogeneous & isotropic) in the

asymptotic future with a positive CC. In that limit the matter becomes

so diluted that for all practical purposes the expansion is determined

entirely by the CC, and the limiting behavior is that of an exponential

expansion of the scale factor. Such a universe inevitably *becomes* a

DeSitter universe in its future limit. (And, apparently, it seems that

our universe *is* such an example).

David Bowman

David_Bowman@georgetowncollege.edu

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