ABSTRACT
We have mentioned in §1.6 that a relativistic quantum theory naturally leads us to field theory. It was also commented there that the structure of classical field theory has some problems, and we should use quantum field theory. Since such theories describe all three fundamental interactions that we are going to discuss, it is imperative that we have an idea of the basic tenets and the main working tools of quantum field theory. In this chapter, we present the important concepts and tools in capsule form. If the reader is already familiar with the methods of quantum field theory, this chapter may easily be skipped. Other readers will feel unhappy at many places in this chapter, where results will appear without proofs. Unfortunately, there is no alternative: if we have to do justice to the discussion of quantum field theory, we would require so many pages that the reader would feel even more unhappy. So, a reader unfamiliar with quantum field theory will have either to accept some results and understand how a result can be applied without understanding how it is derived, or consult a quantum field theory book to obtain more details.
