Foundations of Physics, VoL 16, No. 8, 1986
Book Review
Fourth Workshop on Grand Unification (Proceedings). Edited by H.A. Weldon, P. Langacker, and P.J. Steinhardt. Birkh/iuser, Boston, 1983, ix + 415 pp., $29.95 (cloth). The remarkable successes of QCD and of the Glashow-Weinberg-Salam SU(2)× U(1) model as gauge theories of the strong and electroweak interactions has encouraged theorists to seek a grand unified theory incorporating these interactions and other, much weaker ones which in general lead to proton instability (the as-yet unsuccessful search for which is still being pursued with vigor on three continents) and can have important cosmological implications as regards the formation of matter and structure in the very early universe. Since 1980, a yearly series of workshops has been convened in the United States to take stock and discuss the various theoretical and experimental issues relevant to the true unification of elementary particle interactions. The Proceedings of the Fourth Workshop on Grand Unification, held in 1983 at the University of Pennsylvania in Philadelphia, still serve as a useful reference for many important aspects of the field. Traditionally, the workshops lay equal emphasis on theory and on experiment. While some of the talks describe the negative results of unsuccessful searches for such exotic phenomena as proton decay, neutrino and neutron-antineutron oscillations, and neutrinoless double beta decay, many others still stand as valuable concise reviews of a number of important aspects of unified theories. W. Marciano provides a careful review of the predictions of various specific grand unified theories as regards the expected proton lifetime. Data accumulated since this workshop serve to almost rule out the simplest, minimal SU(5) model, but do not yet invalidate nonminimal versions of the theory. A. Grant gives an overview of the general experimental effort devoted to the search for proton decay, including some possible future techniques. Also very important are the two papers of T. Gaisser and 851 0015-9018/86/0900-0851505.00/0© 1986 Plenum Publishing Corporation
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Book Review
A. Dar discussing the angular distribution and flux of atmospheric neutrinos which can initiate reactions in the detectors which can mask a proton decay signal. The separation of signal and background is not easy, and the effects of atmospheric neutrinos an important issue. Magnetic monopoles, expected in grand unified theories, were discussed by three speakers. A. Goldhaber provides an illuminating discussion of the connection between monopoles, gauge fields, and anomalies, as relevant in the so-called Rubakov effect, the catalysis of proton decay by GUT monopoles. C. Tesche, of IBM, describes her group's effort at detecting a cosmic magnetic monopole flux by means of superconducting magnetometers, and P. C. Bosetti reviews the status of the unsuccessful searches for monopoles using a number of different, more conventional methods, while providing much useful background material on the interactions of monopoles with matter. F. Boehm contributes an authoritative review of the, as yet also unsuccessful, searches for neutrino masses and oscillations. P. Sikivie, in his talk, gives a compact description of invisible axions and how they arise in one solution of the strong CP problem, with special emphasis on bounds on their properties obtained from cosmological considerations. Cosmological issues to which grand unified theories bear were reviewed in three very useful talks. M. Turner gives a completely self-contained review of the inflationary big bang cosmology and how it helps solve a number of old and well-known conundrums of the standard Big Bang model. J. Primack provides an easily accessible introduction to the dark matter and galaxy formation problems, showing what types of new particles expected in grand unified theories can help with a combined resolution of the puzzle of what comprises most of the (unseen) matter in the universe, and how the irregularities that led to galaxies arose in the first place within the framework of homogeneous, isotropic cosmologies. This last subject is also addressed in a more technical review paper of A. Szalay. Finally, five talks covered the rapidly expanding field of research provided by supergravity, superstrings, and theories of the Kaluza-Klein type with extra, compactified space-time dimensions. G. Kane provides a still useful capsule review of the phenomenology of supersymmetric theories, while J. Polchinski describes how spontaneously broken supergravity can lead to plausible models of the electroweak unification scale, now of the more hopeful frameworks in which to do this. M. J. Duff and S. Weinberg describe the properties of higher-dimensional theories and how gauge interactions can arise from a generalization of general relativity to more than four dimensions, ~ la Kaluza-Klein. Finally, there is the ringing endorsement of D = 10 superstring theories (which are currently much in vogue) given by E. Witten.
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All in all, this book covers much material that is still of great use to practitioners of grand unified theories, and should find a place in the wellstocked research library. Serge R u d a z
School of Physics and Astronomy University of Minnesota Minneapolis, Minnesota 55455
