Answer Happy

2) Consider the following (not to scale) diagram: dhe 7 7 Comoving scale 2 2 6 3 3 5 5 ay INR tdec., DM te tdec time Figure 1: Evolution diagram (i) Explain briefly (no need for calculations - just give a physical expla- nation) the meanings of Ay and Aj. (4/20) (ii) What are the physical meanings of toq and dec? (4/20) (iii) Consider a universe without dark matter. For each of the regions numbered (1) - (8), describe the evolution of a small perturbation in the baryon density in this region. (6/20) (iv) Consider a universe with cold dark matter (ACDM). For each of the regions numbered (1) - (8), describe the evolution of a small perturbation in the dark matter density in this region. (6/20) Note: in parts (iii) and (iv), there is no need to calculate the scaling laws of the evolution of the perturbations. Just provide brief descriptions.