## Sunday, 24 July 2011

### Big Bang for Dummies (Including Me)

Those who have been following this blog right from the start will be aware that one of my many long term goals is to understand the Big bang properly almost line by line This has been an on off project and quite often I get bogged down or TMA's and other bits of maths distract me. I last looked at this back in December 2010 when I got bogged down in trying to calculate the Riemann Tensor for the Robertson Walker Metric. I attempted to do this directly from the basic equations as this involves calculating 64 connection coefficients this is an exercise in tedium usually just quoted in many textbooks. The method whilst guaranteed to work is soul destroying to say the least and not much insight to the physics is given. There are more efficient methods based on Coordinate Free differential geometry but this takes a while to master.

Fortunately I remembered a method which I read about when I first got into General Relativity based on comparing the Equations of motion derivable from a Lagrangian and the equations for the Geodesics. I'll expand on this later I hope to work it out over August in the mean time for those new followers of mine I enclose a link to a summary of the main features of the big bang I worked out about 4 years ago. This amazingly shows that to capture the essential features of the Big Bang you do not need General relativity or sophisticated particle physics. It is somewhat surprising that an estimate of the hydrogen helium abundance can be got on the basis of Newtonian Physics and the Boltzmann distribution. Ok the interpretation of the Newtonian approach is a bit dubious but it still ends up with the Friedmann equations. Anyway I offer it to my fellow bloggers in the hope that they will find it instructive  it shouldn't require to much background in either physics or maths

http://dl.dropbox.com/u/16049029/Bigbang_simp.pdf

Enjoy

Chris.

(PS Apologies for my Grasshopper mind I'll probably put Galois theory on the back burner for now as I've now got another obsession )