Sets

Abstract

Much of algebra can be done using only very little set theory; all that is needed is a means of comparing infinite sets, and the axiom of choice in the form of Zorn’s lemma. These topi cs occupy Sections 1.1 and 1.2. They are followed in Section 1.3 by an introduction to graph theory. This is an extensive theory with many applications in algebra and elsewhere; all we shall do here is to present a few basic results, some of which will be used later, which convey the flavour of the topic.