Some Applications of Number Theory to 3-Manifold Theory

These are the extended notes of a talk I gave at the Geometric Topology Seminar of the Max Planck Institute for Mathematics in Bonn on January 30th, 2012. My goal was to familiarize the topologists with the basics of arithmetic hyperbolic 3-manifolds and sketch some interesting results in the theory of 3-manifolds (such as Labesse-Schwermer, Calegari-Dunfield, Dunfield-Ramakrishnan) that are obtained by exploiting the connections with number theory and automorphic forms. The overall intention was to stimulate interaction between the number theorists and the topologists present at the Institute.