Where Strings Came From and What They Are

Abstract

It is not possible to cover all the developments of string theories in four lectures. Moreover, not everyone in this audience is working on strings, which makes it difficult to select a level of presentation that might be interesting to the experts, and at the same time be pedagogically helpful to those who would like to learn some of the basics of string theory. Thus, it is necessary to restrict severely the topics, and I have done so with the nonexperts in mind. To indicate the level, I am told that I should not assume knowledge of the Nambu action [1], although many of you certainly know it in detail. So, in discussing general string formalism, I will omit technical details and many important topics and, instead, attempt no more than a qualitative description. When discussing compactification, I will describe the simplest toroidal schemes, including some of the Lie algebraic background. Nothing will be said about Calabi-Vau manifolds, which have been so interesting in the context of the heterotic string.