A13w 2 0 2a3 3 2 h012t 0 for radia8on

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: egrated backwards w.r.t. 8me to find t(a). 5/28/13 UW, ASTR 323, SP13, Eric Agol ©2013 4 Expansion rate •  In a flat Universe where one component dominates, da 1/2 − (1+3w )/2 dt = H0Ω0 a •  Integra8ng this (for w≠- 1) gives: a da!a!(1+3w )/2 = ∫ 0 2a3( 3( )/2 ) = H0Ω1/2t 0 •  For radia8on, w=1/3, so a∝ •  For cold maRer, w=0, so a∝ 5/28/13 UW, ASTR 323, SP13, Eric Agol ©2013 5 Expansion History 102 ΩΛ=0.685 101 a∝eHt 100 Ωm,0=0.315 a(t) 10-1 a(t)= 10 (1+z)- 1 10 a∝t2/3 -2 -3 a∝t1/2 10-4 Ωr,0=4.6e-5 10-5 10-8 10-6 10-4 10-2 100 102 H 0t 5/28/13 UW, ASTR 323, SP13, Eric Agol ©2013 6 Proper distance •  r(t)=a(t)r0 - instantaneous separa8on – _________ to measure! •  What we can measure is the trajectory of light for which dl =___ (‘null geodesic’). In a flat Unive...
View Full Document

This document was uploaded on 04/05/2014.

Ask a homework question - tutors are online