Axions for amateurs

Abstract

Axions are an increasingly popular topic in theoretical physics, and are sparking a global experimental effort. In the following I review the motivations for the existence of axions, the theories underlying them, and the methods to search for them. The target audience is an interested amateur, physics undergraduate, or scientist in another field, and so I use no complicated mathematics or advanced theoretical topics, and instead use lots of analogies.

Comments: 28 pages, invited review for Contemporary Physics. v2: small corrections and minor additions