Quantum field theory is the basic mathematical framework that is used to describe elementary particles. It is a cornerstone of modern physics.
　　This textbook provides a complete and essential introduction to this subject. Assuming only an undergraduate knowledge of quantum mechanics and special relativity， it is ideal for graduate students beginning the study of elementary particles， and will also be of value to those in related fields such as condensed-matter physics.
　　The step-by-step presentation begins with basic concepts illustrated by simple examples， and proceeds through historically important results to thorough treatments of modern topics such as the renormalization group， spinor-helicity methods for quark and gluon scattering， magnetic monopoles， instantons， supersymmetry， and the unification of forces.
　　The book is written in a modular format， with each chapter as self-contained as possible， and with the necessary prerequisite material clearly identified. This structure results in great flexibility， and allows readers to reach topics of specific interest easily. The book is based on a year-long course given by the author and contains extensive problems， with password-protected solutions available to lecturers at www.cambridge， org/9780521864497.
　　MARK SREDNICKI is Professor of Physics at the University of California， Santa Barbara. He gained his undergraduate degree from Cornell University in 1977， and received a Ph.D. from Stanford University in 1980. Professor Srednicki has held postdoctoral positions at Princeton University and the European Organization for Nuclear Research （CERN）.