This text aims to provide an introduction to the subject of quantum field theory without the complication of introducing its application areas such as elementary particle physics or statistical physics at the same time.
It explains those features of quantum and statistical field systems that result from their field-theoretic nature and are therefore common to different physical contexts. The reader is supplied with practical tools for carrying out calculations as well as a discussion of the meaning of the results.
An approach emphasizing the simplest models is used, progressing to discussion of real systems before mentioning more general and rigorous conclusions. The book is structured around carefully selected problems, which are solved in detail. The central concept is that of effective action (or free energy in statistical physics), and the main technical tool is the path integral, although other formalisms are also mentioned. A knowledge of particle physics phenomenology is not required. T