| The present universe has Ωm0 = 0.23 and Ωr0 = 8.4 × 10-5. Calculate the redshift z at which Ωm = Ωr (the epoch of matter-radiation equality). | [2] |
| The differential equation for structure growth shows that density perturbations should grow ∝ a in a matter-dominated universe. Explain why, despite this, one might expect that structures would not start to grow until the epoch of recombination at z ∼ 1100. | [2] |
| How does the recognition that most of the matter in the universe is non-baryonic cold dark matter affect the growth of structure? | [3] |
(2006 Resit Q7(b).)