ABSTRACT
We have seen in the previous chapters that while chiral fields in the large N limit describe free particles, gauge theories describe, or are described by, noninteracting strings. The notion of “free string” is far from being trivial, and actually, we have used this term before rather loosely. It is the purpose of this chapter to present the theory of strings. Unfortunately this theory is not yet completed. So, we shall give a review of existing results and indicate the possible directions of future development.
