de Broglie vs Bohm --authentic quotes from Louis de Broglie, forefather of a portion of the original quantum theory, on how his revised (nonlocal) pilot wave theory diverges from what is today called bohmian mechanics
If it is true that de Broglie helped Bohm, and that Bohm helped de Broglie, it's also true that we have here two, not just one, branches of nonlocal pilot wave versions of quantum physics, when it comes to pictures of eg the particle and the wave. Here's a quick walk-through of what de Broglie wanted to visualize of quantum phenomena, after his own words have been quoted. This is the first time this particular series of comments by Nobel laurate and one of the topmost physicists in the 20th century, Louis de Broglie, have been made easily available on the internet. For physicists who are groomed in a tradition that is sceptical to the importance of this interpretation: remember that when we look aside from which theory came first, then, for any set of theories predicting the same type of things (so far), we must apply other criterions than 'does it predict something new'. Among these: elegance; a sense of wholeness as regards other plausble theories; intuitiveness. And this is a question not of dogma, but of letting science, in the best spirit of both being sceptical and open-minded, look calmly at alternatives. Note: in the comments before and after the verbatim quotes from de Broglie's hugely interesting and well-written 1956 book (from the translated 1960 publication by Elsevier Co. Pub.), we use the phrase 'pilot wave theory' (or pilot-wave theory) to cover a broad range of theories. In de Broglie's own vocabulary, the pilot-wave theory was a watered-down version of a grander theory that he called the Double Solution. Our comments are in agreement with common word usage, in which we regard any theory that attributes such as both position and momentum to particles at all times together with some form of nonlocal guiding wave or field to account for quantum phenomena, as a pilot wave theory or interpretation. Quotes occupying a few pages of a book of some 300 pages are here given, and, to further honor the copyright to the Louis de Broglie foundation of all the texts of Louis de Broglie, neither complete footnotes nor complete proof- reading of this typed-in document is provided. The typing-in was completed in June 2016, and after this point, only the LINKS section, with link to the World Wide Web for further reading and to the catalogue numbers of the books and articles most referred to, will be updated, to accomodate changes on the web. USE THIS FOR PRIVATE EDUCATIONAL PURPOSES. This is put forth in a benefit-for-all spirit and not intended for commercial use nor for mass-reproduction in a different medium. Please retain this document as a whole if you make a private backup of it. --SRW Excerpts provided in June, 2016 by S.R. Weber. Link section at the completion of this document by intent updated yearly. SHORTEST POSSIBLE SUMMARY Across the world most physicists are now appreciating the consistency of an alternative form of quantum theory to the mainstream version due to, among others, N.Bohr and W.Heisenberg, which is called, for instance, bohmian mechanics, and also, the de Broglie/Bohm pilot wave theory or interpretation. However, de Broglie came with two pilot wave theories--one, in the 1920s, which David Bohm rediscovered in the early 1950s and improved upon, so that it became consistent. And a second, in the 1950s, which is due to the revision that Louis de Broglie himself undertook of his own theory after reading Bohm's work and responding very positive to parts of what Bohm had done. Louis de Broglie, Nobel laurate and one of the great forefathers of all quantum theory, profoundly disagreed with Bohm at one key point, at least. A few physicists have published articles on this point. Most have no inkling about this difference at all. In this page,, the source material is all available at the fingertips for anyone to study further on their own. This then, is to remedy what may be of importance for future physics studies of the pilot wave type of theories, esp. now that, in the past couple of years, this type of interpretation has begun to receive some empirical support, and renewed praised from mainstream science journals and magazines. BACKGROUND Most people who have studied quantum theory know that, among the major interpretations, bohmian mechanics is one of them. This is also called the de Broglie/Bohm theory, because of the ideas Louis de Broglie put forward in the 1920s, and which, in part, Bohm rediscovered and improved upon in his own theory in the early 1950s. While there is no doubt that Louis de Broglie read and enjoyed and found it beneficial the work that David Bohm had done, and built on it, and that, in turn, David Bohm and his colleges also read Louis de Broglie and benefitted from his work, including his use of metaphors, it is, at the time of writing this (2016), only a few voices in the physics community who suggest that de Broglie's pilot wave theory is, in fact, a different theory than that of David Bohm causal or, as he later preferred, ontological interpretation. As I had the great joy of meeting David Bohm and his wife Sarel several times (before I adopted the pen name SRWeber; they knew me as Henning Braten), I could have asked him about these things when I had the chance. As it is, it was only by chance, many years after Bohm's death, that I came across the book by Louis de Broglie on the matter, where he refers in detail, and graciously, to Bohm's work, while at the same time spelling out how his view of reality is at several interesting points absolutely different. I recalled then that a physicist at the University of Bristol, years, earlier, had pointed it out to me, that these two theories are indeed distinct. As I indicated, but very few physicists have as yet worked on this distinction (a notable exception is the work of A.Valentini, who however has also worked on his own version of pilot wave theory along entirely different lines than that which de Broglie proposed). While in 2016 what I here set forth is not at all common knowledge, I should hope that within some years, the internet flourishes not only with descriptions of "de Broglie/Bohm" theory, but also with descriptions of the unique features of the de Broglie theory of the 1950s as compared to the theory due to David Bohm and the further developments by B.Hiley, C.Dewdney, A.Steinberg and the many others who have now, across the world, taken up the pilot wave theory in one form or another and begun seeing it as a serious alternative to the Bohr/Heisenberg interpretation of quantum phenomena. All these developments can be mutually fruitful when we give space to each one of them in a caring scientific philosophical light without the needless emotionality that sometimes characterises the socalled 'scientific discourse'. This is not about voting in favour or against Bohm, but rather trying to honor the role of the human mind in a first-hand sense doing informal visualisations of reality as whole, when we also engage in precise formalisations of parts of these visualisations and compare the predictions that may arise from some of these formalisations when bridged, by additional assumptions, to some empirical domains. Bohm has opened some doors, but as I see it, the work on rethinking physics has barely begun. Many people seem to regard Bohm's work as the fulfillment of that which de Broglie started. However, what is the case is that though the formalism at some levels are identical, the theory of reality is, indeed, a very different one. And in these days, when empirical studies, such as by A.Goldberg, are beginning to arise to as to compare the mainstream interpretation of Bohr and Heiseberg against bohmian mechanics, and where one might surmise that physicists might soon be able to formulate at least slightly different predictions in some realms involving nonlocality so as to check one interpretation against another (supposing, for instance, that a physicist undertood to reformulate a part of bohmian mechanics), it may be of value to actually consider what Louis de Broglie himself said on the matter. After extensively researching all available fully public internet sites referring to Louis de Broglie, I have found that essential points of de Broglie are neither presented in original form nor in a properly re-presented form by others and have undertaken to remedy this by creating this page. This document is, I hope, clear enough even though it is not proofread--neither my own comments nor the quotes or excerpts from the important 1956 book of Louis de Broglie, where he disassociates himself from an 'easy' pilot wave interpretation and goes in for a more 'heavy' pilot wave interpretation, in contradistinction to what I perceive is most of the works of David Bohm on this matter. Louis de Broglie being who he is, means that we should consider again whether he has all the time harbored a 'better' pilot wave theory hidden under his (rather private) heading of 'The Double Solution'. AS FOR COPYRIGHTS: The de Broglie quotes are here given in a purely educational spirit and you find in the links section also links to the copyright holders of all published material of Louis de Broglie, and these must be consulted for any further use of this material. While the quotes are somewhat longer than that which is typical of a book not yet fully released in the public domain, it is after all only a fraction of the book that is here, and only the text part, not the equations, and as it will help the cause of understanding the brilliant thinking of Louis de Broglie it will probably only help the cause of the copyright holders that these excerpts of the 1960 translation are given here. Before we go on, let me say that David Bohm read and referred to de Broglie's 1950s work. But Bohm emphasized the points of connection and agreement, and he also found it fruitful to bring further a metaphor over the particle that de Broglie proposed. This is understandable in a context where Bohm's work had been rediculed instead of researched upon for years, until J.S.Bell began to clear up how Bohm had been able to do something that most physicists at the time regarded as 'proven impossible', due to deduction by J.v.Neumann in the 1920s. Bohm, finding a degree of support in de Broglie's work, naturally emphasized this support, seeing that it came from a very important character in the scientific community. However, what with a number of physicists now regarding bohmian mechanics as a viable alternative, in some respects, to the Copenhagen Interpretation, and philosophers such as H.Putnam has, in 2005 [in Brit.J.Phil.Sci., 56:615-634], called pilot wave theory quite 'elegant', we are in a situation where it would be interesting to refine variations of these various interpretations so as to suggest possible differences in empirical predictions. And in order to give full credit to the full range of possibilities in so doing, we should pay outmost attention to the fact that while Bohm's equations and de Broglie's equations are, on the surface, the same, de Broglie has a wholly different picture of reality. In this different picture, one is led to think differently about particles and waves than how it is done in bohmian mechanics. For a clear-headed empiricial physicist with a good grasp of the ideas involved, this may suggest entirely different ways of going about it to do such as to pinpoint the tracks of particles or the possible reality of the pilot wave. Indeed, one can surmise that within some decades, there may be different 'renditions' of pilot wave theory, some more in tune with Bohm, some more in tune with de Broglie, some bringing in new concepts altogether, all of which lends themselves to suggest slightly or possibly very different empirical predictions in exceptional quantum- physical experiments of a type not yet encountered. I have my own work, my own more informal theory of the whole, which I call "super-model theory", and naturally hope that this will also receive the attention it deserves in due course. This, by the way, leans more on de Broglie's pilot wave theory than on bohmian mechanics, but brings in several new concepts to relate to such as quantum biology (I'm working on a new presentation of this theory these months and will, when it is done, present a book in .pdf form at the following location: -- but by June 2016 this has not been finished yet). Be sure to look at the link section at the completion of this page. This link section will be checked about yearly and updated moderately. Louis de Broglie wrote an article in French on the same themes that he develops rather more deeply in the 1956 book, a couple of years before he wrote that book. This article has been translated and with the permission of the Louis de Broglie Foundation, been submitted to the public domain, and is the first of the links given underneath the quotes from the book. After the quotes, we will briefly summarize, in a slightly updated language, what Louis de Broglie actually stated as to the difference. Another point of interest: if you look at the developments in modern physics incl. quantum theory from about 1960 to now, in this half-century and more, most of the general thoughts about quantum theory and indeed also, most of the questions raised by Louis de Broglie, could more or less be written today, with the exception of many footnotes added as to variations of equations and efforts to do such as to get the dependency on measurements away from quantum theory, and additional mentioning of such as many-worlds interpretations and so on. And the status of Einstein's theories are, if anything, more confirmed than ever; and there are, of course, many new formal results where additional bridges between his type of theories and forms of quantum field theory, and such, have been erected, but these things are chiefly in the terreign of formalistic achievements. Also, the presence of lists of quarks and other assumedly fundamental particles alongside a set of equations do not postulate a new philosophical grip on the situation, as much as a systematization of a range of new empirical results largely within the worldview as chiselled out in those early days. As a result, the question of interpretation of quantum phenomena is, if anything, as hot as ever. PHOTOS OF THE 1956 BOOK AND THE 1960 ENGLISH TRANSLATION
EXCERPTS FROM THE ENGLISH TRANSLATION OF THE 1956 BOOK Note: the link to the worldcatalogue id of the 1960 translation copyright Elsevier Publishing Company is given in the link section at the completion. The copyright holders for Louis de Broglie material in general is the de Broglie Foundation where contact info is given in link 3. The following excerpts are for private educational purposes. For any mass or commercial distribution, please contact copyright holders as given in the link section first. All following quotes are from Non-Linear Wave Mechanics, A Causal Interpretation by Louis de Broglie, transl. by Arthur J. Knodel and Jack C. Miller, Amsterdam, 1960, Elsevier Publishing Company, Library of Congress Catalog Card Number 59-12588. The page numbers refer to the hardcover (1st) edition. This is a translation from Une Tentative D'interpretation Causale et Non Linaire de La Mecanique Ondulatoire (La Theorie de la Double Solution) by Louis de Broglie, Gauthier-Villars, Paris, 1956. Confer, as said, the link section for the page for this book. There are, in de Broglie's book, a few reference to numbered bibliographical references and to footnotes underneath some of the pages; for simplicity, these are here not included; please consider getting the whole book (292 pages plus appendix etc) to study also these. Textual translation points: Only text, not equations, are included. The greek letter named Psi, when mentioned inside the prose text of de Broglie, is here written as "Psi", rather than by the greek character, so that what follows is an ascii-text-friendly set of excerpts; italics are shown _as this_, which is typical also in eg. texts. [Indeed, it would be fruitful if the de Broglie Foundation contacts and submits to them the book in full, both in its French original form and in the form of the English translation, in agreement with Elsevier, for there is material here of vital importance for the education of the scientists and thinkers of the future.] A couple of places de Broglie utilises, in the midst of prose text, something that requires such as an elevated small font, and then we have improvised a notation like [RAISED TO] to indicate this textual phenomenon, but it is fairly obvious the few places it arises. The book itself is dense with equations, but we regard the chief points to come forth in the text. [Any grammatical and spelling errors are due to the typing-in process, and probably not at all in the original 1960 book.] ORIGINAL QUOTES FROM LOUIS DE BROGLIE'S 1956 BOOK IN THE 1960 TRANSLATION From PREFACE: [..] As early as 1923 I had clearly seen that the propagation of a wave must be associated with the movement of every particle, but the continous wave--of the type familiar in Classical Optics--which I had been led to consider and which became the Psi wave of ordinary Wave Mechanics, did not seem to me to describe the physical reality accurately; only its _phase_, related direclty to the motion of the particle, seemed to me of fundamental significance, and that is why I had named the wave which I associated with the particle "the phase- wave"--a designation that is completely forgotten today, but which at that time I believed entirely justified. However, as the work of other scientists led to further progress in Wave Mechanics, it became daily more evident that the Psi wave with its continous amplitude could be used only in statistical predictions. And so, little by little, there was an increasing trend towards the "purely probabilistic" interpretation, of which Born, Bohr and Heisenberg were the chief advocates. I was surprised at this development, which did not seem to me to fulfill the "explanatory" aim of theoretical physics; and that is what led me, around 1925-1927, to believe that all problems of Wave Mechanics required a set of two coupled solutions of the wave equation: one, the Psi wave, definite in phase, but, because of the continous character of its amplitude, having only a statistical and subjective meaning; the other, the u wave of the same phase as the Psi wave but with an amplitude having very large values around a point in space and which, precisely on account of its spatial singularity (a singularity, moreover, which may not be one in the strict mathe- matical sense of the term) can be used to describe the particle ob- jectively. In this way I obtained, in agreement with Einstein's concepts, what I had always believed must be sought: a picture of the particle in which it appears as the center of an extended wave phenomenon involving the particle in an intimate way. And, thanks to the theo- retically postulated parallelism between u and Psi waves, the Psi wave, it seemed to me, preserved all the statistical properties that had quite rightly been attributed to it. [..] [..] I should like this line of thought, abandoned for some twenty-five years now and believed to lead to an impasse, to be carefully re-examined to see whether, on the contrary, it may not be the pathway that might lead to the true Microphysics of the Future. Chapter I. The basic ideas of wave mechanics From page 3: 1. Point of departure The idea which, in my 1923-1924 works, served as the point of departure for Wave Mechanics was the following: Since for light there exists a corpuscular aspect and a wave aspect united by the relation- ship Energy = h times frequency, where h, Planck's constant, enters in, it is natural to suppose that, the matter as well, there exists a cor- poscular _and_ a wave aspect, the latter having been hitherto unrecog- nised. Chapter III. First principles relative to the probabilistic interpretations of Psi waves From page 29: 1. The central problem in the interpretation of Wave Mechanics From the very beginnings of the study of Wave Mechanics, the problem of the exact significance to be attributed to the Psi wave was seen to be fraught with great difficulties. It was immediately apparent that it was not possible to consider the Psi function as a physical quan- tity in the old sense--for example, as representing the vibration of some medium. [..] For [..] particle systems, the Psi wave is propagated in a configura- tion space, which is an abstract and fictitious space. The more the formalism of employing the Psi wave became apparent, the more it appeared as a kind of formal and subjective representation making possible the evaluation of the probabilities of certain results of measurement. We will have occasion to show in the course of studying this probabilistic interpretation of the Psi function that this wave-func- tion, defined in the usual fashion as a solution of the linear equations of propagation mentioned in the preceeding chapter, can by no means be considered an objective reality, but only as an element having the same subjective qualities as the probabilities it represents, an element suspectible to variations dependent upon the knowledge of the person employing it. The overriding question, then, is to find out whether the probabil- istic interpretation of the Psi wave, which unquestionably leads to exact predictions, constitutes a "complete" representation beyond which there is no point in seeking an objective description of reality, or whether, on the contrary, the description of phenomena by the ex- clusive use of the Psi wave is "incomplete" and must make room for a more profound and detailed description of physical reality. We will have occasion to return more than once to this problem. From page 48: 5. Remarks on the Wave Mechanics of systems of particles [..] Schroedinger's idea of identifying the Psi wave of a system in con- figuration space at first shocked me very greatly, because, configura- tion space being a pure fiction, this conception deprives the Psi wave of all physical reality. For me the wave of Wave Mechanics should have evolved in three-dimensional physical space. [..] The [..] Psi wave in configuration space [..] is a purely imaginary way of representing wave phenomena which, in point of fact, take place in physical space. Chapter VI. Various aspects of the probabalistic interpretation of wave mechanics From page 63: 4. The notion of complementarity (Bohr) [..] The idea of complementary, although a bit elusive, is an interesting one. Attempts have been made to apply it in various fields--a pro- cedure that is not always entirely safe. But, from the fact that measur- ing processes do not permit us to assign a position and a state of motion simultaneously to a particle, are we necessarily obliged to conclude that, in reality, the particle has _neither position nor velocity_? From page 70: 7. Von Neumann's theorem [..] The examination of this question led me--and on this point I am in agreement with David Bohm--to think that von Neumann's dem- onstration implies a hypothesis that is not absolutely unavoidable [..]. Chapter VII. Objections to the purely probabalistic interpretation of wave mechanics From pages 74-79: 2. Einstein's objection at the 1927 Solvay Congress At the Solvay Congress of October 1927, Einstein raised a very striking objection to the purely probabalistic interpretation of Wave Mechanics. [..] In Einstein's example, the particle would in a sense be spread out in a virtual state in the space beyond the screen. At the moment an effect localized at A takes place, the particle would, so to speak, condense at that point in order to produce an observable phenomenon. [..] It is thus legitimate to consider Einstein's example as a very serious objection to the present interpretation of Wave Mechanics--one that has never been clearly answered. 3. The example of Einstein, Podolsky and Rosen There have been lively and interesting discussions, in which very eminent scientists have participated, on the subject of "correlated" systems, that is, of systems which, once having been in interaction find themselves subsequently separated from each other, but in states with probabilities that are no longer independent. [..] Bohr's reasoning, on occasion rather nebulous, contains a number of questionable assertions. [..] Chapter VIII. Introduction and program From pages 89-91: 1. History of the theory of the Double Solution [..] So I boldly laid down a hypothesis--that of the Double Solution-- according to which the linear equations of Wave Mechanics admitted two kinds of solution: the continuous Psi solutions one normally thinks of--the statistical nature of which was beginning to come clearly apparent at that time, thanks to the work of Born, and "singularity" solutions that would have a concrete meaning and be the true physical representation of the wave-particle dualism. Particles would then be _incorporated_ in an extended wave phenomenon. For this reason, the motion of a particle would not obey the laws of Classical Mechanics according to which the particle is subject only to the actions of forces exerted on it in the course of its trajectory, without experiencing any effect from the existence of obstacles that may be situated at some distance outside the trajectory. In my conception, on the contrary, the motion of the singularity was to be dependent on all the obstacles that hindred the free propagation of the wave phenomenon surrounding it, and there would result from this a reaction of the wave phenomenon on the particle--a reaction expressed in my theory by the appearance of a "quantum potential" entirely different from the potential of ordinary foces. And in this way the appearance of interference and diffraction phenomena would be explained. Unfortunately the development of this theory of the Double Solution presented great mathematical difficulties. For that reason, when I was requested to present a paper on Wave Mechanics at the Solvay Physi- cal Congress held in Brussels in October 1927, I contented myself with a presentation of my ideas in an incomplete and dilluted form which I called the "pilot-wave theory". [..] And I used the term "pilot-wave theory" for the theory limited to the postulation of the existence of the particle and the Psi wave, with no further reference to a wave containing a singularity. This watered- down version of my original conception happened to coincide exactly with the one put forward at the same date by Madelung in his hydro- dynamical interpretation of Wave Mechanics, but this simplified ver- sion had far less interest and profundity than my initial ideas on the Double Solution. My presentation at the Solvey Congress was received unfavorably, and the purely probabalistic interpretation of Bohr, Born and Heisenberg supported by Pauli, Dirac and others, was very clearly the one preferred by most of the scientists present. [..] On the other hand, my original theory of the Double Solution, by distinguishing the Psi wave, with its probabalistic and subjective char- acter, from the singularity-wave (u wave), which was to be a de- scription of objective reality, might possibly supply the more classical type of interpretation I was after. But I knew only too well that the theory of the double solution likewise involved numerous difficulties, especially when it came to the existence and form of singularity-waves and to their relation to the Psi waves, or when one had to interpret in terms of singularity-waves interference experiments of the Young-slit type, etc. Confronted with all these difficulties, I gave up these attempts, for their outcome struck me as far too problematical. From 1928 on I embraced Bohr's probabalistic interpretation as the basis of my per- sonal research, my teaching and my books. During the summer of 1951, there came to my attention, much to my surprise, a paper by David Bohm which appeared subsequently in The Physical Review. In this paper Bohm went back to my theory of the pilot-wave, considering the Psi wave as a physical reality. He made a certain number of interesting remarks on the subject, and in particular, he indicated the broad outline of a theory of measurement that seemed to answer the objections Pauli had made to my approach in 1927. My first reaction on reading Bohm's work was to reiterate [..] the objections [..] [..]. Takabayasi, moreover, subsequently took up these objections in papers where he developed aspects of Bohm's theory in an interesting way. Chapter IX. Principles on the theory of the double solution From page 111: 8. The guidance formula and the theory of the pilot-wave [..] If there exists--as the theory of the Double Solution assumes--an ob- jective wave phenomenon represented by a wave u, having a singular region, whose propagation is modified by the action of external fields and by the presence of obstacles (interference and diffraction), one can then conceive that everything takes place as if the trajectory of the particle, which is really imposed upon it by the propagation of the u wave, were determined by the phase of the Psi wave. But it is impossible to assume that it is the Psi wave that regulates the motion of the par- icle because this Psi wave is only a probability representation with a fictious and subjective character. We will be obliged to return repeatedly to this important question. We will see especially that, in his paper of January 1952, David Bohm has again taken up the theory of the pilot-wave, assuming that the Psi wave is a "physical reality". This point of view seems inadmissable to me, even when we are concerned with the noramlized Psi wave of Wave Mechanics for a single particle, and then, all the more so when it is a matter of the Psi wave of a system of particles in configuration space. From page 172-173: 4. Supplementary observations The principle of Bohm's demonstration consists of pointing out that the Psi wave of a particle or of a system is always slightly perturbed by the existence of very small external actions (weak collisions, for ex- ample) and of assuming that these small perturbing potentials repre- sent these actions with their entirely random fluctuations. It is here a question of potentials of a classic type, but Vigier has quite correct- ly pointed out that one could consider small perturbing quantum po- tentials resulting from small random fluctuations in boundary condi- tions (for example, the thermal motion of the walls of a receptacle). [..] It is curious to note that in this way there would be achieved a synthesis of the conceptions of the causal theory and of Einstein's frequently reiterated affirmation that the successes of the statistical interpretation of Wave Mechanics imply underlying particle-movements of a Brownian character. [A footnote on page 173; SQUARE is our rendering of the elevated 2:] Since 1954, when this passage was written, I have come to support wholeheartedly an hypothesis proposed by Bohm and Vigier. According to this hypothesis, the random perturbations to which the particle would be constantly subjected, and which would have the probability of presence in terms of SQUARE [ |Psi| ], arise from the interaction of the particle with a "subquantic medium" which escapes our observations and is entirely chaotic, and which is everywhere present in what we call "empty space". From page 175: Chapter XIV. Pauli's objections to the theory of the pilot-wave 1. The discussion of the pilot-wave theory at the Solvay Congress of October 1927 [..] However, when I was asked to present a paper on Wave Mechanics at the Solvay Congress that was to be held in Brussels during October 1927, I balked at the difficulties in mathematically justifying the double-solution point of view, and I contented myself with a presenta- ion of the pilot-wave point of view. At the Solvay Congress, while a few of the "old guard" (Lorentz, Einstein, Langevin, Schroedinger) insisted on the necessity of finding a causal interpretation of Wave Mechanics--without, however, coming out in favor of my efforts-- Bohr and Born, along with their young disciples (Heisenberg, Dirac, etc.), came out categorically in favor of the new purely probabalistic interpretation that they had developed, and they did not even discuss my point of view. Pauli was the only one to present a definite objection to my theory, and he did so by examining the case of a collision between a particle and a rotator, which Fermi had studied a short while before. [..] From page 182: 3. Pauli's objection to the guidance formula [..] So I had perceived, as the quotation given above shows, that the answer to Pauli's objection would have to rely on the fact that the wave-trains are always limited. And this idea has been taken up again by Bohm in his recent Papers. From pages 183-185: 4. The abandonment of attempts of a causal interpretation of Wave Mechanics after 1927 In the months that followed the Solvay Congress of October 1927, I abandoned the pilot-wave approach that I had maintained. But not because of Pauli's objection. For, as I say, I thought I had found the way in which to overcome it. Rather, I abandoned the pilot-wave ap- proach for other, more general, reasons. [..] A summary of these reasons follows. The particle, conceived as a physical reality, cannot, I said to myself, be guided by the Psi wave, whose probability-representational character (at once subjective and conditioned by the knowledge of its user) had been plained revealed by the development of Wave Mechanics. This fictitious character of the Psi wave was already forced upon us for the Psi wave associated with only a single particle in ordinary space. It thus became all the more inescapable in the case of the Psi wave of a system, which is propgated in the system's configuration space, which is purely abstract. [..] Such were the considerations that led me, in 1928, to abandon the pilot-wave theory as untenable. The original form of my ideas, _i.e._ the theory of the Double Solution, did not seem to me to run into the same difficulties, but I had become convinced that its mathematical justi- fiction, if it were possible, was beyond my capacities. [..] And then in January 1952 appeared the two Papers by David Bohm. We will now analyze the main arguments of these two Papers. From pages 186-187: Chapter XV. Bohm's theory of measurement and the statistical schema of the causal theory 1. Bohm's papers of January 1952 The two articles published simultaneously by David Bohm in January 1952 in _The Physical Review_ once more focussed attention on the question of the interpretation of Wave Mechanics. In these pa- paers Bohm reverts to the pilot-wave theory in the form I had given to it at the 1927 Solvay Congress. He assumes that the Psi wave is a physical reality (even the Psi wave in configuration space!). I have already stated why such an hypothesis appeared absolutely untenable to me. [..] Bohm's papers contain still other statements that strike us as du- bious. For example, he is undoubtably right in saying that on a very reduced scale (10 [RAISED TO]-13 cm or less the guidance formula, and consequently the staistical significance of the Psi, could very well no longer hold, but the modification of the equation of propagation which he proposes as a remedy seems to me artificial. Nevertheless, if Bohm's work calls for certain reservations, it also has merits that seem to me unquestionable. In particular, he has once more focussed attention on the possibility of the an interpretation of Wave Mechanics different from the one that is now prevalent, and he has shown that it is not pointless to submit the whole question to a pains- taking re-examination. [..] These are a few of the interesting results developed by Bohm in his two papers, but the most original part of his work is certainly his theory of measurement, which we are now going to analyse. From page 188: 2. The theory of measurement according to Bohm [..] This study of interaction led Bohm to analyze measuring processes which, by and large, amount to the interaction of a particle and a measuring apparatus (pp. 179-184 of the second paper). The performance of the measurement establishes "correlations" between the particle's final state and the final state of the measuring apparatus, so that the observation of the final state of the apparatus permits us to deduce the final state of the particle. From page 193: [..] From the point of view adopted here, every quantity Q of the par- ticle has a well defined value in its initial state, but this value is a "hidden variable", since, generally, every attempt at measuring it will result in its modification. If by some exception a measuring apparatus does allow us to obtain a value of Q without modification, then that apparatus will modify the values of all the quantities P that do not commute with Q. So we must carefully distinguish between the "hidden variables"-- which in the causal theory as well as in Classical Physics, would at every instant characterize the particle's position and motion--and the "observables" in Dirac's sense, which are the values of these quantities obtainable by a measuring operation. This shows, in accordance with certain ideas of Bohr but in a totally different manner, the importance of measuring operations. WHAT DID LOUIS DE BROGLIE REALLY SAY ABOVE? OUR OWN COMMENTS Please note our statement on how we use the phrase "pilot wave theory" in the little note we put on top of all this. Did the de Broglie of the 1950s understand nonlocality? The word 'nonlocality' became fashionable only long after J.S.Bell (in taking apart the hidden assumptions in Von Neumann's proof) in the 1960s showed that the assumption of locality must be negated in order to have a hidden variable interpretation of quantum theory; Bell then went on to point out the importance of Bohm's work; and subsequent research by Alain Aspect and others in the 1970s and onwards showed that (apart from questions of interpretation), entanglement has macroscopic effects and cannot be regarded as merely a mathematical fiction. It is certain that de Broglie of the 1980s understood and accepted nonlocality. It is perhaps not so that he wanted to push any such point in his 1950s work. It is in any case clear that the pilot wave in three dimensions can exhibit nonlocal or entangled, and also coherent, behaviour, in a way that's compatible both with the work of de Broglie and with bohmian mechanics. The fact that the wave, as seen by de Broglie, exists (also) in three dimensional space doesn't preclude the possibility of entanglement, as long as our whole reality picture isn't confined to just the manifest dimensions. As to young de Broglie's relationship to the somewhat older Bohr: de Broglie, as one of the five top physicists in the first half of the twentieth century, was said to be in bed, nursing a headache, when Bohr, inside Bohr's venerable institute in Copenhagen, went to his room and pushed him (according to W. Heisenberg in a diary that Heisenberg published after WWII), for hours, until de Broglie gave up pursuing the pilot wave interpretation. According to the present book by de Broglie, he never gave it up, he merely regarded it as unfinished work, that had to be worked more on in order to be presented more fully. And it was Bohm's genius that set de Broglie aflame again, some twenty or twenty-five years later, to begin to do just this. Comments to the preface: The distinction between what de Broglie calls a purely psychological construct, Psi, and the wave u, is what he develops further on in the book. de Broglie regards the probability densities, with its many dimensions, not as having a direct reality in the physical situation, even though the equation is there. Bohm, on the other hand, chooses to attribute reality here; and as such, Bohm's view of the reality of quantum situation at once calls for complexities of a daunting kind in the image. They agree that there's a reality to the particle and its position variables also when they are not subject to measurement, but they disagree in what is around it. The wave u is simpler in terms of visualisation than Psi. Bohm wants Psi to be real; de Broglie wants Psi to be a calculated inference with only u to be real. This opens for variations in how one interprets the connection between particle and pilot wave, a point made by some physicists but so far understood by very few. It is a point that is of vital importance when one realises that formalisms cannot be the theory itself, rather our ideas of reality compose the theory, with formalisms as illustrations only of some aspects of it. As for agreement with Einstein's concepts--here de Broglie refers to the desire of Einstein, shared with Karl R Popper and indeed a large portion of those engaging in the theory of science, that science, first and foremost, is about picturing reality and offering formalisms so as to reason around these pictures and so as to check predictions also, but not so that the formalism is taken to be the theory itself. On the other hand, it is well known, and has been ever since the work by J.S.Bell in the 1960s, that nonlocality--entanglement--a feature of quantum wholeness or coherence in which the speed of light is not respected--are more or less part of quantum theory-- implicitly in all versions, but more explicitly in the pilot wave type of interpretations; and, moreover, that this nonlocality feature is at odds with the picture of reality that Einstein sought to implement throughout all essential branches of physics. Einstein called it a 'ghosthly action-at-a-distance'. While nonlocality need not imply any signal transmission, due to fluctuations that impede on signals relayed nonlocally, and thus may not in terms of formalism contradict Einstein's formal postulates, it is a foreign object in the vision of an only locally interacting field that Einstein sought to implement. As many physicists have further noted, nonlocality is a term that implies that distances are covered not just faster than light, but at no time at all, and while there's not any empirics as yet to indicate that nonlocality should be considered something of an overstatement, a modified quantum theory in the future, with modified predictions, relating to superb new empirical instruments, may succeed in producing discernment in this area, and may call for a qualification in the use of the word 'nonlocal'. But, back to Louis de Broglie's ideas here: the disagreement with the spirit of Einstein's theories is more profound in the de Broglie/Bohm line of development, than in the Heisenberg, Bohr, Born line of thinking, since this feature of action-at- a-distance is more explicitly present. However, since Einstein's formalisms and approach to visualizing reality have different starting-points than quantum theory, by and large, seeing these theories together is formally very complex; but thanks to much work by many physicists, some formal unification at some levels have taken place between the Copenhagen Interpretation of quantum theory and features of Einstein's General Relativity. This type of intense work has not yet been put into any of the pilot wave interpretations, at the time of writing this [2016]. And so, this has sometimes been used as an argument against the bohmian mechanics--that it is both more explicitly against Einstein's theories (even though the latter have had a very broad range of confirmations and few disconfirmations)--and also formally, less easy to tie in with Einstein's work. At heart of this particular conflict with Einstein's work is the idea of reality, and, if we elevate the ideas into critical attention, for the moment looking away from formalisms (as we should, since the theories in any case are not reducible to mere formalism), we must, as David Bohm repeatedly did, ask whether we should not regard Einstein's vision of reality as something which is an appearance rather than the deep reality, something which is an outcome of a reality that is fundamentally not a process of a speed-of-light organised locally interacting field. Bohm suggested, at a very general level, that quantum theory broadly calls for a 'new order' in our visualisation of reality, and this broad metaphysical understanding is indeed compatible with many branches of development in more recent physics. This is also compatible with where we might want to take Louis de Broglie's pilot wave theory and where we might want to take bohmian mechanics. Thus, for instance, one can imagine that the speed of light is an organising principle of sorts, where processes deeper and faster than that are at works to give rise to the manifest particles and waves. When, in a broad range of examples, only local forces are found, that is due to a certain feature of this deeper reality; but when there are phenomena of coherence and entanglement over distance, this is simply another feature of this deeper reality, and perhaps, in a sense, more near this deeper reality. Einstein's picture is then regarded as not absolutely true, but rather a visualisation of how things tend to be when quantum coherence can be disregarded. Quantum coherence may however not be just one phenomenon, for we are never at any point in mere scientific theorising over found empirics where we can with certainty say, "this is the final type of process, there is nothing more to it than this." It may be, and indeed it is the view of this writer (made explicit in the Super-Model Theory), that quantum physics is but a flicker of a flicker of a vastly different reality; however, as it stretches rather to the maximum what the technology of today can do fine measurements on, it is unrealistic that by applying a minimalist (Occam's Razor) type of theory of science, we'll ever come to appreciate much of such a theory. Instead, we must ask whether we can find other features than empirical measurements (such as human intuition at a direct, logical level) to distinguish one proposal from another in terms of what is best to assume. In the last sentence of the foreword, de Broglie looks to the future and considers the present proposals--including, it seems, the whole of quantum mechanics--to be a mere pathway to what he calls a "microphysics". Let us take this seriously into consideration, all the more when we appreciate that in global fashion, the word "quantum" has been, and still is, something of a rave. Quantum physics, theory, mechanics, may be just a pathway, to a microphysics in which different concepts are found to be essential. And let us be clear that what de Broglie's ideas of physics cohere with Einstein and he would not put his signature on a physics which is merely a loose collection ideas vaguely explaining some dense equations that, for some reason or another, seem to work. The latter type of physics--string theory is a recent example--is but a furthering of the Heisenberg-Bohr-Born attitude that de Broglie, along with both Einstein and Schroedinger, and of course along with Bohm, Bell and a host of others, find worthy of severe criticism as candidate physics. String theories and other theories whose metaphors and ideas flutter lightly around heavy formalisms are not de Broglie's "true microphysics of the future". These are but the logical consequence of the movement away from a natural visualisation of the world along the lines that Bohr, Born and Heisenberg argued for, more out of respect for Einstein's principle of the limits of the speed of light, than out of a metaphysical deliberation to rob human theorising of a reality picture. Comments to quotes from chapter III and onwards: One might argue that Louis de Broglie seems needlessly 'tied up' to what we in this age of computation over matrices of many dimensions and with so many many- dimensional theories and forms of metaphysics hanging over humanity in a sort of creative cloud, could consider an 'old school' form of liking of three dimensional space. But no matter how accustomed we get to the phrase 'many dimensions', the fact remains that imagining a wave in three dimension is simpler and more intuitively obvious than imagining it in a space that has as many dimensions as their are particles, to take one example. And, thinkers in theory of science, from Popper to Quine and beyond, and before them, have always put a premium on simplicity. If it is--and Louis de Broglie seems to suggest that it is--possible to visualize a wave in three dimensions in such a manner as to give rise to the probability densities associated with Psi, then by all means our theory of reality should, given the candidate of this 3d wave and the many-dimensional Psi wave in configuration space, prefer that which, all other things being similar, is most simple. In that way, it's not a question of being 'old school' when three dimensions are brought in: it is rather a question of sticking to Einstein's axiom that science is chiefly an activity of our imagination, looking for beauty and correlations in our imaginary map of reality, and only then coming up with equations. And so, in discerning the wave that gives rise to the Psi wave as connected more to reality while the Psi wave is an artefact of our formalisms, he is indicating his chief disagreement, as I read him and as I read Bohm, with what is now called bohmian mechanics. He agrees with Bohm in the fundamental pursuit for a theory that relates to the reality, or the ontology, beyond the equations: but disagrees in how this reality should be related to the formalisms that we have. In his view, we ought to have something simpler than what Bohm suggests in order to account for the whole range of phenomena, which in modern language, after John Bell's work in the 1960s, is also called 'nonlocal' phenomena. It's important to realize that de Broglie nevertheless regards the whole idea of giving particles position values and such in terms of what is sometimes called 'hidden variables' (in order to respect Heisenberg's uncertainty relation), as entirely the right stuff. He agrees with Bohm also in the way Bohm treats the measurement situation--by means of a mutual transformation between the measured objected and the measuring instrument in a way that, due to the entanglements and Planck's constant h--and as such congratulates Bohm upon solving what the young de Broglie himself couldn't do with his early pilot wave theory. The ripe, post 1952 de Broglie pilot wave theory is however incorporating this part of Bohm's work and diverges in the aforesaid manner in the reality picture. This difference, as said, may be considered less important than the grand question of whether the Copenhagen Interpretation got its main metaphysics wrong or not: but I disagree. It is exactly in these little questions that we may come up with essential differences that, at some point, may be significant in providing instances of confirmation and of disconfirmation so as to select between these theories, in one way or another. The little differences become great the moment we have new forms of measurements involved, alongside new proposed variations of the theories in various directions. (My own proposed super-model theory is an intuitive summary of a worldview that incorporates the de Broglie pilot wave interpretation alongside a number of other assumptions on a wholly different set of underlaying premises.) LINK SECTION Link #1: The translation to English in 1960 of de Broglie's 1956 book was published (see info above) by Elsevier Pub. Co., Amsterdam; New York, and has this listing at The copyright for the above excerpts are also to Elsevier, in case of anyone wanting to include them in the format of such as a book, or reproduce these excerpts in any massive way. This, then, would help, alongside Link#3, to get you in contact with copyright holders of the material: Link #2: de Broglie's article from 1953, translated to English, where he discusses some of the points more clearly elucidated in his 1956 book, which in excerpts is given above. The Interpretation of Wave Mechanics with the help of Waves with Singular Regions The paper appeared in a collection of papers entitled Scientific Papers Presented to Max Born on his retirment from the Tait Chair of Natural Philosophy in the University of Edinburgh, published in 1953 (Oliver and Boyd). Link #3: Annales de la Fondation Louis de Broglie has a number of articles in original French and some translations, and contact info for the copyright holders of the written material of Louis de Broglie. For any commercial or massive redistribution of the above quotes, one must contact the Louis de Broglie Foundation first, and one should find contact info through the following link: Link #4: Next article is a translation of a french article de Broglie wrote decades later (he died in the late 1980s), where he, among other things, declares that he stands firm on the postulate that the pilot wave interpretation of quantum phenomena is for him more correct than the other interpretations. Interpretation of quantum mechanics by the double solution theory, Annales de la Fondation Louis de Broglie, Vol. 12, No. 4, 1987. Link #5: Next is an article written by David Bohm and Basil Hiley where the points of agreement between the approach of Bohm and de Broglie are emphasised. This is a very good introduction to bohmian mechanics, and Hiley, C.Dewdney and others helped this by contributing with appealing computer plottings of quantum potential and possible particle trajectories. Considering the rough time Bohm's causal interpretation had had, one can understand that agreements are, at this stage, what is pointed out. However, it is severely incomplete as far as presentation of Louis de Broglie's own revised pilot theory goes, even though it refers to the 1956 book of de Broglie, in that the difference in the reality picture and the interpretations of the formalisms are not elaborated upon, but rather underplayed. This I can say even as I continue to warmly support the work by my friend the late David Bohm, and how it is followed up by Basil Hiley (whom I have also had the pleasure of meeting) and many others in a steadily increasing flood of interesting publications all over the world, in about every scientific journals and magazine there is, at many universities (not in the least in Germany), and by more and more books. The change in the scientific community from how I remember it about when I visited Bohm at Birkbeck, in 1986 and twice more (before we invited him in Oslo for a weekend seminar on his favorite theme of 'Dialogue'), is quite startling. And work such as by the canadian A.Goldberg, both on the empirical and theoretical level, to dismiss the idea that the trajectories in bohmian mechanics are anywhere near 'surreal', has contributed to a surge of renewed interest. Anyway, here's the promised article info and what should be a good working link to a pdf of this important 1982 article: Title: The de Broglie Pilot Wave Theory and the Further Development of New Insights Arising Out of It by David Bohm and Basil Hiley in: Foundations of Physics, Vol. 12, No. 10, 1982. Questions? Email srw at