Radiation: The Photon in the Classical Context
暫譯: 輻射：古典背景下的光子

This self-contained book covers all of fundamental classical electrodynamics in a much broader sense with a wide range of applications. The theory is developed from the concept of a photon using methods of field theory. In particular, the propagator, monitoring the photon, describes the entire process, in a time evolutionary manner, from the time a photon is emitted to the time it is detected in an experiment, avoiding the use of plane waves. While, the so-called derived vacuum-to-vacuum transition amplitude provides a way for carrying computations involving radiation and describes the interactions of the theory. One learns that what one calls electric and magnetic fields emerge simply from the formalism as a consequence of gauge invariance and, in passing, Maxwell's equations simply pop up. Does this mean that one has to forget concepts of electric and magnetic fields in such a formalism? - of course not !. The power of the vacuum-to-vacuum transition amplitude, and the propagator, together with these fields, give rise to a much rich language to study classical electrodynamics. The volume concludes with a fascinating chapter involving the cosmic background radiation originated when the Universe was about 380,000 years old and cooled down enough so that neutral atoms were formed and photons became mere spectators free to move and are right here around us as we observe them today. Electrodynamics, over the years, was invariably developed again and again beginning with Maxwell's equations, and a reader will find it refreshing to experience the present treatment emphasizing physical clarity, simplicity of derivations, and elegance of formalism. This book is intended for physicists, all those in the sciences and engineering, for graduate/advanced undergraduate students and professionals alike.