# I Entropy production equation

Tags:
1. Nov 28, 2016

### shinobi20

From the paper, https://arxiv.org/abs/astro-ph/0305015, on page 3,
How did the author arrived with equation (10)? By using the radiation density and (8) defined in the previous paragraph,

$ρ_r = \frac{3}{4}Ts ~$ (radiation density) I think the author got it wrong ($ρ_r = \frac{4}{3}Ts ~$)
$T\dot s + 3HTs = Γ \dot φ ^2~$ (8)

We have, $~T \dot s = \frac{4}{3} \dot ρ_r ~$ and $~ \frac{4}{3} \dot ρ_r + 4Hρ_r = Γ \dot φ ^2~$

But why is that in the paper it is written as $~ \dot ρ_r + 4Hρ_r = Γ \dot φ ^2~$?

Also, how did the author get the radiation density $ρ_r = \frac{3}{4}Ts ~$ by saying that we set $~δm_T = 0~$ in (2)?

2. Dec 3, 2016