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-   -   Friedmann equation (http://www.physicsforums.com/showthread.php?t=129282)

blumfeld0 Aug20-06 01:29 PM

Friedmann equation
 
Hi does anyone know a website or paper where the friedmann equation is derived from the robertson walker metric?
it should have the calculation of atleast a few of the christoffel symbols etc

thanks

blumfeld

Parlyne Aug20-06 04:17 PM

The Friedmann equation can't be derived from the RW metric. It is a constraint on that metric, which is derived from the GR field equations. In other words, you can't derive it wityout the stress-energy tensor.

renerob Aug20-06 05:52 PM

You may be interested in reading Relativity Demystified by David McMahon. On page 161 the following problem is worked out: Consider the Robertson-Walker metric and suppose we take the Einstein equation with nonzero constant, find the Friedman equations.

blumfeld0 Aug21-06 08:16 AM

Hello Thank you for the reply
So the friedmann equation is a constraint on the metric derived from the stress energy tensor
what specific stress energy tensor is used? just the diagonal
{-rho, p, p ,p }?
also are theere any websites that have the derivation of this constraint equation from einsteins field equations>?
i will also try to check out the book you recommended
thanks!


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