Foundations of Physics, VoI. 15, No. 2, 1985
Book Review The Wave-Particle Dualism. Edited by S. Diner, D. Fargue, G. Lochak, and F. Selleri. D. Reidel, Dordrecht, The Netherlands, 1984, vii + 566 pp., $76.00 (cloth).
The book, in the series Fundamental Theories of Physics, represents the Proceedings of an international symposium held in Perugia on April 22-30, 1982, organized by the Louis de Broglie Foundation and the University of Perugia and dedicated to Louis de Broglie on his 90th birthday. There are 31 papers devoted to various interpretations of quantum mechanics, hiddenvariable theories, probabilistic and axiomatic questions, and tentative crucial experiments. The wave-particle dualism, introduced for light by Einstein in 1905 and extended to matter by de Broglie in the early twenties, has been the subject of heated discussions all through the 20th century. The value of a recent collection of papers on the matter should be judged by its adequacy in fulfilling two conditions: to be representative of the present ideas and to have a high enough level of quality. In the opinion of this reviewer, both conditions are realized by the book. It is true that there is a bias towards heterodoxy in quantum mechanics, but this is unavoidable as long as orthodox people tend to believe that wave-particle dualism is a well established fact, perfectly integrated into quantum theory and, therefore, devoid of actual interest except for the historians of science. Of course, a lot of people do not accept this opinion. Papers in the book can be divided into three main groups. About onethird of the papers deal more directly with wave and particle behavior of light and matter. Another third is devoted to the related and fashionable subject of separability and locality. The remaining papers form a more heterogeneous group with an emphasis on tentative solutions to the interpretation problems of quantum mechanics. Historical aspects of the wave-particle dualism are reviewed in the papers by G. Lochak ("De Broglie's initial conception of de Broglie waves"), P. W. Milonni ("Wave-particle duality of light: a current perspective"), F. Selleri, and, to a lesser extent, others. 229 0022 9018/85/0200-0229S04.5o/o © 1985 Plenum Publishing Corporation
230
Book Review
A number of papers review experimental results that show clearly the wave-particle dualism of light (the long paper by Milonni is remarkable) or matter (H. Rauch reports on recent results with thermal neutron interferometry and A. Steyerl on those with ultracold neutrons). Tentative crucial experiments are proposed for testing standard quantum mechanics against forms of dualism more along the lines of thought of de Broglie. F. Selleri ("Gespensterfelder") and G. Tarozzi ("From ghost to real waves: a proposed solution to the wave-particle dilemma") suggest experiments in order to test the existence of void or virtual waves. A. Gozzini's paper deals with similar experiments. Two kinds of semiclassical phenomena are reviewed by M. V. Berry ("Structures in semiclassieal spectra: a question of scale") and V. Aquilanti ("Atomic collision experiments at the borderline between classical and quantum mechanics"), while a novel approach to pure wave propagation is presented by L. S. Schulman ("Ray optics for diffraction: a useful paradox in a path integral context"). The mathematical development of de Broglie's ideas on the simultaneous existence of waves and particles is presented in a clear form by D. Fargue ("Permanence of the corpuscular apperance and nonlinearity of the wave equation"). A related paper is the second one by P. Lochak ("Could solitons be adiabatic invariants attached to certain nonlinear equations?"). More philosophical is the paper by S. Diner ("The waveparticle duality as an interplay between chaos and order"). The orthodox solution to the problems posed by the wave-particle dualism is the quantal measurement theory. A nice criticism of that theory is the paper by F. Fer ("A critical analysis of the quantum theory of measurement"). On the other hand, a model for the reduction of the state vector by means of a nonlinear Schr6dinger equation is presented by P. Pearle. The interplay between particles (i.e., localized objects) and waves (nonlocalized entities) is certainly related to the problem of nonseparability and nonlocality, a subject of active research in the last 20 years, after the discovery of Bell's theorem. In the reviewer's opinion, some confusion has been created by some authors (frequently mathematicians) who insist that the meaning of Bell's theorem is to show an incompatibility between quantum and classical (i.e., Kolmogorovian) probabilities, the problem of locality being irrelevant. The point is that there is some hope for a classical alternative to quantum mechanics as long as locality is not violated. Therefore, the contrast between local realism and quantum mechanics is the crux of Bell's theorem, a point not stressed enough in the papers of the book. The proofs of a contradiction between classical and quantum probabilities (in particular, the nonexistence of joint probabilities for incom-
Book Review
231
patible quantum observables) are reviewed in two formal papers by L. Accardi ("The probabilistic roots of the quantum mechanical paradoxes") and P. Suppes and M. Zanotti ("Causality and symmetry"). Related papers are those of M. D. Srinivas ("Quantum interference of probabilities and hidden-variable theories"), S. Bergia ("On the possibility of extending the tests of quantum mechanical correlations") and D. Aerts ("How do we have to change quantum mechanics in order to describe separated systems?"). A drastic solution to the nonseparability problem is considered by C. W. Rietdijk with the assumption of a "superdeterminism" leading to a wholeness of all processes in the Universe. The experimental side of separability is dealt with by A. Aspact who reviews his now widely known experiments. F. Falciglia, L. Fornari, A. Garuccio, G. Iaci, and L. Pappalardo describe the experiment proposed by Rapisarda, delayed by his untimely death. J. Six proposes a test of nonseparability of the K0K 0 system. Finally, the book contains a number of papers of more difficult classification: P. Caldirola ("Introduction of the cronon in the theory of the electron and the wave-particle duality"), M. Roos ("On the superposition principle and its physical content"), O. Costa de Beauregard ("CPT revisited: a manifestly covariant presentation"), S. P. Gudder ("Waveparticle duality in the quark model"), W. H. Zurek ("Destruction of coherence in nondemolition monitoring: quantum watchdog effect in gravity wave detectors"), M. Boiteux ("Nonlocal hidden variables and nonlocal gauge theories"), and H. P. Noyes ("A finite particle number approach to physics"). Emilio Santos Departamento de Fisica Te6rica Universidad de Santander Santander, Spain
