Cosmology lecture notes

Cosmology textbooks sit in one of two camps.
The introductory books do a good job of describing the expanding universe, but tend to be less detailed on the hot Big Bang and structure formation.
Meanwhile, advanced books which cover these topics assume prior exposure to both general relativity and statistical mechanics.

This is a course on cosmology, aimed at final year undergraduate students.
It assumes a background in neither general relativity nor statistical mechanics.
The full lecture notes come in around 170 pages.
Please do email me if you find any typos or mistakes. 1.
The Expanding Universe:

The Cosmological Principle:

The cosmological constant was first introduced by Einstein in 1917 in an attempt to construct a static cosmology.
This was over a decade before Hubble’s discovery of the expanding universe. ̈ a 4⇡G tells us that a static universe is only possible if ⇢ = 3P .