Lecture IV

Having considered the Friedmann equations, let’s now turn to the expansion history of the Universe. In this lecture, we’ll study phenomenologically how the expansion of the universe relates to the matter content. We will then study how distances in cosmology are measured. In an expanding universe, even the concept of “distance” needs to be treated carefully. We’ll focus on the “pure theory” here, and then in the next lecture look at the observations that have been used to measure H0, Ωm, and ΩΛ. Our objective will be to compute, for a given cosmological model, D(z), i.e. the relationship between the distance to an object and the redshift.