Particles And Fields

Particles and Fields Devro Lunrf Technion, Israel Institute of Technology, Haifa, Israel 1968 INTERSCIENCE PUBLISHERS a division of John Wiley & Sons New York London Sydney Coovrieht @ 1968 by John Wiley & Sons' Inc'- be Ali;i:nil;";;;".d- No part of this book mavnor nor transmitted' ;;;;il;;A-tv urv meins, language..without hachine. t i;;;il;;J-i"t; "^*--^of the publisher' *.itten the permission Library of Congress catalog card number 68-22312 sBN 470 556420 and?rinted by Set "-1.on Monophoto Filmsetter Ltd., Bristol, England w.'Aiio'*rr"itt ,'' l r l.t! l;,, t:,r2, 3Ll t r'-I .-r ! I il t:l I l-l;l Foreword --.i, 't The quantum theory of fields was invented about forty years ago to give expression to the relativistic quantum mechanics of the radiation field. Within a decade it had established itself as the theoretical framework for the description not only of electromagnetic interaction, but also of nuclear interactions. Within another two decades it was extended to cover the weak interactions as well. There have been several occasions in the past when it appeared that the quantum theory of fields was inconsistent and had to be abandoned. The difficulties with quantum electrodynamics were circumvented by the development of renormalization theory towards the middle of this century and it was shown that meaningful and accurate predictions about the properties of electrons in electromagnetic fields could be made. The basic difficulties themselves were not resolved; instead one succeeded in reformulating the theory in such a fashion that the embarrassing infinities of the quantum field theory did not appear explicitly. The successful exploitation of analytic properties to develop physically satisfactory approximation methods for strong interactions and the population explosion among hadrons diverted attention from the basic problems of the quantum field theory of interacting systems. Grouptheoretic and dispersion-theoretic methods of calculation had a moderate amount of success. On the basis of this, the possibility was seriously entertained that the quantum theory of fields was irrelevant for the dynamical description of subnuclear phenomena. Recent years have seen a resurgence of interest in the quantum field theory. Dynamical calculations based on suitableLagrangians for interacting fields have had a certain amount of success. Considerable attention is now being devoted to an examination of basic field theory; and some of the older problems are being analyzed anew. Field variables like currents and fields are being allotted their rightful place as fundamental dynamical variables. vi Foreword is appropriate that this elegant presentation of orthodox quantum field theory by my friend Dr. David Luri6 is appearing at this juncture. It It contains an account of the elements of field quantization and covariant perturbation theory in the first half of the book. One cannot fail to note the graceful simplicity of the treatment of this traditional domain. The expert would also note the explicit discussion of the spin 312 and spin 1 fields. The treatment of the renormalization theory, reduction formulae and spectral representations brings out the essential ideas without getting lost in mathematical details. The discussion of coupling constants and sum rules is quite attractive. But it is most pleasing to see the excellent treatment of the BetheSalpeter equation, of bound states and of the functional method; in most existing books on field theory these topics are dismissed without any ceremony. On the whole the book does a very creditable job of presenting the quantum theory of fiel