Simple Modules: Schur's Lemma

This lecture covers the concept of simple modules over a unital ring or a unital associative algebra. It explains torsion elements, torsion-free modules, free modules, simple rings, and simple associative algebras. The lecture also delves into endomorphisms of modules, Schur's lemma for modules, and Rieffel's lemma on the bicommutant of a simple algebra.