Lectures on families of Dirac operators and applications

These are the notes for a minicourse taught at the 2022 ICTP summer school `Frontiers in Geometry and Topology’. The goal is to introduce families of Dirac operators and how they can be used to study interactions between geometry and topology. In particular, we discuss the index theorem for families of twisted Dirac operators, and its applications to metrics of positive scalar curvature and the three-dimensional Weinstein conjecture.