# Homework Help: In a radiation dominated era, how do I show this?

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1. Oct 17, 2015

### Phil1093

As above. In a radiation dominated how do I show this equation?
http://i.imgur.com/nMwxvD5.png (It's easier for me to post the image to imgur than use latex.

I know g is the relativistic degrees of freedom.
I think that the scale factor a(t) is proportional to 1/t
and that a(T) is proportional to 1/T

I think it might have something to do with,

s= s/v = (E+P)/KbT
and s=(1+w) Pc^2/KbT

but other than that, I don't know where to start :/ Any help would be appreciated :)

2. Oct 22, 2015