The Many-Worlds Interpretation of Quantum Mechanics (Princeton Series in Physics, 63) by Bryce Seligman Dewitt | (PDF) Free Download

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A novel interpretation of quantum mechanics, first proposed in brief form by Hugh Everett in 1957, forms the nucleus around which this book has developed. In his interpretation, Dr. Everett denies the existence of a separate classical realm and asserts the propriety of considering a state vector for the whole universe. Because this state vector never collapses, reality as a whole is rigorously deterministic. This reality, which is described jointly by the dynamical variables and the state vector, is not the reality customarily perceived; rather, it is a reality composed of many worlds. By virtue of the temporal development of the dynamical variables, the state vector decomposes naturally into orthogonal vectors, reflecting a continual splitting of the universe into a multitude of mutually unobservable but equally real worlds, in each of which every good measurement has yielded a definite result, and in most of which the familiar statistical quantum laws hold. The volume contains Dr. Everett’s short paper from 1957, “‘Relative State’ Formulation of Quantum Mechanics,” and a far longer exposition of his interpretation, entitled “The Theory of the Universal Wave Function,” never before published. In addition, other papers by Wheeler, DeWitt, Graham, and Cooper and Van Vechten provide further discussion of the same theme. Together, they constitute virtually the entire world output of scholarly commentary on the Everett interpretation.Originally published in 1973.The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.

User’s Reviews

Editorial Reviews: Review “Peebles applies quantum theory, often in a simple, approximate way, to a variety of interesting problems…. Could prove quite a rewarding book for the more able and motivated student.” ― New Scientist

Reviews from Amazon users which were colected at the time this book was published on the website:

⭐When I was studying physics, some of my fellow students and I were so perplexed by the strangeness of quantum mechanics that we went to our professors for help. But our professors basically said it’s the best theory ever, just compute and don’t ask questions. About 10 years before that, however, a student of John Wheeler at Princeton HAD asked some questions and came up with an answer. Unfortunately, it was so wild that no one believed it and the theory fell into a Black Hole for many years. Now, however, it just might be the favored theory among the greatest physicists.The problem that Hugh Everett saw was that when no one is making a measurement, the world hums happily along according to the Schrodinger Wave Equation, which, for example, tells you the probability of finding an electron at any given place. But when you make a measurement, the wave function collapses, and the probability goes to 1 that the electron is where you measured it. So the world seems to be dual: the Wave Equation and the Collapse of the Wave Equation. Everett saw a way to make the World One always, never Two, at the cost of creating quite a few Worlds each of which would also be One. The way this works is that if quantum mechanics tells us the spin of the electron has half a chance of being Up and half of being Down, and then when we measure it and find it is pointing Up, a new Universe is instantly created in which the spin is Down. Everything in each Universe follows the Schrodinger Wave Equation always. Everett of course died a bitter man with his great idea forgotten by all, but a later student, Bryce DeWitt, stumbled across the idea years later and helped to bring it forward again. This book is a record of that experience, with Everett’s main papers and appreciations of the papers by several physicists. It’s a great intellectual adventure, and you may find yourself captivated by the terrific simplicity of Everett’s Great Idea.

⭐Everrett was a genius way ahead of his time. This compilation includes his papers on the many worlds or many branching or relative state formulation of quantum mechanics. He may not be right. No way to tell experimentally, yet. But his work was a significant and refreshing challenge to the prevailing orthodoxy of the time. The response from the high lords of Copenhagen was to reject his work and trash his career. He went into civil defence. What to do when the nukes start popping. An exercise in pure absurdity and futility. The trashing was by those who take Galileo’s defiance of the church as one of their founding myths. By the way For the record Galileo caved. No fault or blame. Who wouldn’t. The holy catholic inquisition could get very creative with red hot pokers on those who actually did defy them.Also for the record the price of this compilation is ridiculous. It seems to be mostly poor quality photocopies of the original papers. Be warned.

⭐Nice

⭐Very very poor print quality, like a scan at 150dpi then printed on a dot-matrix printer.

⭐great book

⭐I had this book 20 years ago but lost it when my backpack was stolen, now I see it is 100+$ used???? Wow. I would like to get a copy just for Wheeler’s intro piece on Everett, he has a good quote to the effect of (from memory): ‘Physics is the history of Man’s naive assumptions about Nature being shattered one after the other, Everett presents us with one of the most shattering of assumption challenges. ‘ The book also reveals how interpretations of quantum mechanics, are strictly speaking, irrelevant to physics per se. Just as for Newton, interpretations of gravity were irrelevant when he declared: Hypotheses Non Fingo.

⭐This 1973 book includes (1) Hugh Everett III’s 1957 doctoral thesis, (2) a “much larger exposition of his ideas, which was never published,” (3) five papers by other writers, discussing Everett’s ideas.Everett’s larger paper, ‘The Theory of the Universal Wave Function,’ contains this “extremely hypothetical drama”: “Isolated somewhere out in space is a room containing an observer, ‘A,’ who is about to perform a measurement upon a system ‘S.’ After performing his measurement he will record the result in his notebook… A, being an orthodox quantum theorist, then believes that the outcome of his measurement is undetermined and that the process is correctly described by Process 1. In the meantime, however, there is another observer, B… who is in possession of the state function of the entire room… B is only interested in what will be found in the notebook one week hence… At this point, B opens the door to the room and looks at the notebook… he turns to A and informs him … that since [B]s] wave function just prior to his entry into the room and its contents… the result must have been decided only when B entered the room, so that A, his notebook entry, and his memory about what occurred one week ago had no independent objective existence until the intervention by B… A conveys in a colorful manner his opinion of B and his beliefs… by observing that if B’s view is correct, then… the whole present situation may have no objective existence, but may depend upon the future actions of yet another observer.” Everett comments, “It is now clear that the interpretation of quantum mechanics with which we began is untenable if we are to consider a universe containing more than one observer. We must therefore seek a suitable modification of this scheme, or an entirely different system of interpretation.” (Pg. 4-6)Much later, Everett states, “There are… fundamental restrictions to the knowledge that an observer can obtain about the state of the universe. It is impossible to discover the total state function of any physical system, since the process of observation itself leaves no independent state for the system of the observer, but only a composite system state in which the object-system states are inextricably bound up with the observer states. As soon as the observation is performed, the composite state is split into a superposition for which each element describes a different object-system state and an observer with (different) knowledge of it. Only the totality of these observer states… contains complete information about the original object-system state—but there is no possible communication between the observers described by these separate states. Any single observer can therefore possess knowledge only of the relative state function …. Of any system, which is in any case all that is of any importance to him.” (Pg. 98-99)He says of the so-called ‘Copenhagen Interpretation’ of quantum mechanics, “This interpretation … denies the very possibility of a single conceptual model applicable to the quantum realm, an asserts that the totality of phenomena can only be understood by the use of different, mutually exclusive … models in different situations… While undoubtedly safe from contradiction… [this interpretation] is perhaps overcautious. We do not believe that the primary purpose of theoretical physics is to construct ‘safe’ theories at severe cost to the applicability of their concepts, but to make useful models which serve for a time and are replaced as they are outworn.” (Pg. 110-111)He notes, “We should like now to comment on … Einstein’s criticism of quantum theory… he put his feeling colorfully by stating that he could not believe that a mouse could bring about drastic changes in the universe by looking at it. However, from the standpoint of our theory, it is not so much the system which is affected by an observation as the observed, who becomes correlated to the system.” (Pg. 116)He acknowledges, “Once we have granted that any physical theory is essentially only a model for the world of experience, we must renounce all hope of finding anything like ‘THE correct theory.’ There is nothing which prevents any number of quite distinct models from being in correspondence with experience… and furthermore no way of ever verifying that any model is completely correct, simply because the totality of all experience is never accessible to us.” (Pg. 134)He explains, “We thus arrive at the following picture: Throughout all of a sequence of observation processes there is only one physical system representing the observer, yet there is no single unique STATE of the observer… Nevertheless, there is a representation in terms of a SUPERPOSITION, each element of which contains a definite observer state and a corresponding system state. Thus with each succeeding observation (or interaction), the observer state ‘branches’ into a number of different states. Each branch represents a different outcome of the measurement and the CORRESPONDING eigenstate for the object-system state. All branches exist simultaneously in the superposition after any given sequence of observations.” (Pg. 146)In his essay, Bryce DeWitt says of the ‘Schrödinger’s Cat’ argument, “Schrödinger felt that the wave mechanics that led to this paradox presented an unacceptable description of reality. However, Everett, Wheeler, and Graham’s interpretation of quantum mechanics pictures the cats as inhabiting two simultaneous, noninteracting, but equally real worlds.” (Pg. 156)DeWitt says of the Copenhagen Interpretation, “[It] promotes the impression that the collapse of the state vector, and even the state vector itself, is all in the mind. If this impression is correct, what becomes of reality? How can one treat so cavalierly the objective world that obviously exists all around us? Einstein… must surely have expressed himself thus in his moments of private indignation over the quantum theory. I am convinced that these sentiments also underlie much of the current dissatisfaction with the conventional interpretation of quantum mechanics.” (Pg. 159)He points out, “there exists no outside agency that can designate which branch of the superposition is to be regarded as the real world. All are equally real, and yet each is unaware of the others. These conclusions obviously admit of immediate extension to the world of cosmology… The alert reader may now object that the above argument is circular, that in order to derive the PHYSICAL probability interpretation of quantum mechanics, based on sequences of observations, we have introduced a NONPHYSISICAL probability concept, namely that of the measure of a subspace in Hilbert space. This concept is alien to experimental physics because it involves many elements of the superposition at once, and hence many simultaneous worlds, that are supposed to be unaware of one another. [Edward, Wheeler, and Graham] do not in the end exclude any element of the superposition. All the worlds are there, even those in which everything goes wrong and all the statistical laws break down… It is also possible that maverick worlds are simply absent from the grand superposition… It simply may not have enough fine structure to accommodate maverick worlds.” (Pg. 163)He argues, “The traditional way to solve the regression problem is by fiat. One asserts that after the measurement is completed… the state vector COLLAPSES to one of the elements… The collapse of the state vector and the assignment of statistical weights do not follow from the dynamical equations that the dynamical variables of the system and apparatus satisfy. They are consequences of an a priori metaphysics that is imposed on the theory and that may be somewhat adjusted to suit convenience… The trouble with this solution is that physics is no longer physics; it has become metaphysics.” (Pg. 177)He summarizes, “If we are to follow Everett … then we must be willing to admit that even the entire universe may be faithfully represented by … a superposition… Our universe must be viewed as constantly splitting into a stupendous number of branches, all resulting from the measurementlike interactions between its myriads of components… To see what this multi-world concept implies one need merely note that because every cause, however microscopic, may ultimately propagate its effects throughout the universe, it follows that every quantum transition taking place on every star, in every galaxy, in every remote corner of the universe is splitting our local world on earth into myriads of copies of itself. Here is schizophrenia with a vengeance! The idea of [nearly infinite] slightly different copies of oneself all constantly splitting into further copies, which ultimately become unrecognizable, is hard to recognizable, is hard to reconcile with the testimony of our senses, namely, that we simply do not split… The laws of quantum mechanics do not allow us to feel ourselves split.” (Pg. 178-179)This book will be “must reading” for anyone seriously studying the “many worlds” interpretation.

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