An Introduction to Expander Graphs

I will present basic results in the topic of expander graphs, such as the
relationship between expanders and the mixing time of the random walk, the
eigenvalue characterization of expanders, the conductance and the canonical
paths argument, and the expander mixing lemma. I will go over the proofs of two
of them while stating the rest and doing some examples. The things need to
understand the proofs are some theorems in linear algebra (like
Perron-Frobenius Theorem, Minimax theorem of the eigenvalues) and combinatorial
arguments.