What is exactly the drag epoch?
Posted: December 02 2011
Hi Guys,
I don't quite understand the meaning of drag epoch. In Komatsu 2009 paper, it says:
the drag epoch z_{d} and the decoupling epoch z_{*}:
They would be equal only when the energy density of photons and that of baryons were equal at the decoupling epoch – more precisely, they would be equal only when R=3\rho_{b}/4\rho_{\gamma}=1 at z=z_{*}?
What does this mean?
And why does the low density of baryon leads to later of drag epoch?
Thank you!
I don't quite understand the meaning of drag epoch. In Komatsu 2009 paper, it says:
the drag epoch z_{d} and the decoupling epoch z_{*}:
They would be equal only when the energy density of photons and that of baryons were equal at the decoupling epoch – more precisely, they would be equal only when R=3\rho_{b}/4\rho_{\gamma}=1 at z=z_{*}?
What does this mean?
And why does the low density of baryon leads to later of drag epoch?
Thank you!