Mathematical Foundations of Quantum Theory is a collection of papers presented at the 1977 conference on the Mathematical Foundations of Quantum Theory, held in New Orleans. The contributors present their topics from a wide variety of backgrounds and specialization, but all shared a common interest in answering quantum issues. Organized into 20 chapters, this book's opening chapters establish a sound mathematical basis for quantum theory and a mode of observation in the double slit (...) experiment. This book then describes the Lorentz particle system and other mathematical structures with which fun ... (shrink)

Recent developments in quantum theory have focused attention on fundamental questions, in particular on whether it might be necessary to modify quantum mechanics to reconcile quantum gravity and general relativity. This book is based on a conference held in Oxford in the spring of 1984 to discuss quantum gravity. It brings together contributors who examine different aspects of the problem, including the experimental support for quantum mechanics, its strange and apparently paradoxical features, its underlying (...) philosophy, and possible modifications to the theory. (shrink)

It is said that the theory of relativity and quantum theory are independent of each other. Their relationship is like water and oil. Now, it is very important for modern physics to synthesize them. In Physics and mathematics, Super String theory is studied, but instead of it, the tendimensional world appears. Our world is a three-dimensional world. What is the ten-dimensional world? It is more difficult than the string which is of Plank length. In the ten (...) dimensional world, physics is facing darkness and nothingness which man can not explain with the traditional physical words.The solution depends upon philosophy. I tried to synthesize themand succeeded.The following is an outline of my synthesis. 1. Utility and relativity of mathematical truth Mathematical truth is not absolute but relative. In the universe ( outside the solar system ), there is no perfect line. Because, by the gravitation of large astronomical bodies, space and lines are curved. Mathematical figure and numeration depend upon the promise of mankind. These are not absolute. Physics, which is grounded upon mathematics in certainty, is also relative. It expresses not the whole of the universe but a part of the universe. 2. Community and difference between the theory of relativity and quantum theory Community is the negation of absoluteness of physical attributes. Difference is the assessment for mathematics. The theory of relativity relies on mathematics but quantumtheory does not always rely on it. According to circumstances, Niels Bohr and quantum physicists abandoned a frame of reference. 3. The origin of the theory of relativity 4. The origin of quantum theory In short, the theory of relativity and quantum theory are not perfect, they only irradiate a part of the universe. Man can reach the whole of the universe only by the philosophical intuition of nothingness and infinite (the principle of nothingness and love). (shrink)

Papers from the 1994 meeting represent a broad review of contemporary experimental work on quantum phenomena, emphasizing state-of-the-art experimental science. Useful as an introductory manual for young researchers, the volume addresses topics that include: experiments with single and ultracold ato.

The ArgumentThis paper is about the context of Albert Einstein's concerns at the time of a most intense intellectual effort — his own and that of a small group of scientists concerned with classical quantum theory. I describe contemporaneous interactions and differing views about the prospects for and the significance of the First Solvay Congress of 1911 as voiced by major participants. There are two axes around which the paper evolves: the Einstein-Nernst-Lorentz dialogue and the public institutional creation (...) of the “Solvay” stage. In certain ways, this paper is about personal and institutional patronage: the working out of a difficult theoretical impasse requires individual and collective moral support. It is about the forging of the identity of a scientific problem and the personal and institutional setting, the public space, in which this problem was collectively addressed. But I also uncover heuristic playfulness and flexibility which accompanies theoretical change. (shrink)

Development of the Physicist's Conception of Nature P. A. M. Dime When one looks back over the development of physics, one sees that it can be pictured as a ...

The emphasis in this collection is clearly on logic, and this is one reason why it lacks the overall diversity and richness of the 1960 Stanford volume. However, the eight sections do contain much interesting material; in the mathematical logic section Kochen and Specker continue their study of logics appropriate for quantum theory, Vaught presents several new results about the Löwenheim-Skolem theorem, and Büchi studies second-order ordinal theory from the viewpoint of automata theory; the section on (...) foundations of mathematical theories contains papers on higher-order logic by Kaplan and Montague, model theory and ultra-products by Keisler, definability in set theory by Lévy. The topic of the justification of formal theories was the essential topic of the philosophy of logic section: an especially interesting paper is that of A. Robinson in which the present state of Hilbertean Formalism is analyzed, and in which the notion of potential truth is formalized. The section on the philosophy of science contains a single paper, by Hesse, on metaphor and explanation; Braithwaite, Hintikka, Jeffrey, and Kyburg contribute to a lively section on probability and induction; the section on methodology in physical science takes as topics the theory of relativity, causality, and irreversibility. The last two sections, on the philosophy of the life sciences, and on history of logic and philosophy of science, contain, respectively, papers by Davidson and Suppes on meaning and concept formation, and essays by Church and Geach on existential import historically considered and intentionality among the medievals. The collection would have been better if more of the contributed papers had been included.—P. J. M. (shrink)

This edited volume explores the philosophical implications of quantum mechanics. It features papers from venues of the International Ontology Congress up to 2016. IOC is a worldwide platform for dialogue and reflection on the interactions between science and philosophy. The collection features philosophers as well as physicists, including David Albert, Harvey Brown, Jeffrey Bub, Otávio Bueno, James Cushing, Steven French, Victor Gomez-Pin, Carl Hoefer, Simon Kochen, Peter Lewis, Tim Maudlin, Peter Mittlestatedt, Roland Omnès, Juha Saatsi, Albert Solé, David Wallace, (...) and Anton Zeilinger. Since the early days of quantum mechanics, philosophers have studied the subject with growing technical skill and fruitfulness. Their efforts have unveiled intellectual bridges between physics and philosophy. These connections have helped fuel the contemporary debate about the scope and limits of realism and understanding in the interpretation of physical theories and scientific theories in general. The philosophical analysis of quantum mechanics is now one of the most sophisticated and productive areas in contemporary philosophy, as the papers in this collection illustrate. (shrink)

The category-theoretic representation of quantum event structures provides a canonical setting for confronting the fundamental problem of truth valuation in quantum mechanics as exemplified, in particular, by Kochen-Specker’s theorem. In the present study, this is realized by representing categorically the global structure of a quantum algebra of events in terms of sheaves of local Boolean frames forming Boolean localization functors. The category of sheaves is a topos providing the possibility of applying the powerful logical classification methodology of (...) topos theory with reference to the quantum world. In particular, we show that the topos-theoretic representation scheme of quantum event algebras by means of Boolean localization functors incorporates an object of truth values, which constitutes the appropriate tool for the definition of quantum truth-value assignments to propositions describing the behavior of quantum systems. Effectively, this scheme induces a contextualist account of truth in the quantum domain of discourse. The philosophical implications of the resulting account are analyzed. Such an account essentially denies that there can be a universal context of reference or an Archimedean standpoint from which to state the totality of facts of nature. (shrink)

The 1927 Solvay conference was perhaps the most important meeting in the history of quantum theory. Contrary to popular belief, the interpretation of quantum theory was not settled at this conference, and no consensus was reached. Instead, a range of sharply conflicting views were presented and extensively discussed, including de Broglie's pilot-wave theory, Born and Heisenberg's quantum mechanics, and Schrödinger's wave mechanics. Today, there is no longer an established or dominant interpretation of quantum (...) theory, so it is important to re-evaluate the historical sources and keep the interpretation debate open. This book contains a complete translation of the original proceedings, with background essays on the three main interpretations of quantum theory presented at the conference, and an extensive analysis of the lectures and discussions in the light of current research in the foundations of quantum theory. The proceedings contain much unexpected material, including extensive discussions of de Broglie's pilot-wave theory (which de Broglie presented for a many-body system), and a theory of 'quantum mechanics' apparently lacking in wave function collapse or fundamental time evolution. This book will be of interest to graduate students and researchers in physics and in the history and philosophy of quantum theory. (shrink)

Is it possible to approach quantum theory in a 'therapeutic' vein that sees its foundational problems as arising from mistaken conceptual presuppositions? The book explores the prospects for this project and, in doing so, discusses such fascinating issues as the nature of quantum states, explanation in quantum theory, and 'quantum non-locality'.

This book is a critical introduction to the long-standing debate concerning the conceptual foundations of quantum mechanics and the problems it has posed for physicists and philosophers from Einstein to the present. Quantum theory has been a major infulence on postmodernism, and presents significant problems for realists. Keeping his own realist position in check, Christopher Norris subjects a wide range of key opponents and supporters of realism to a high and equal level of scrutiny. With a characteristic (...) combination of rigour and intellectual generosity, he draws out the merits and weaknesses from opposing arguments. In a sequence of closely argued chapters, Norris examines the premises of orthodox quantum theory, as developed most influentially by Bohr and Heisenberg, and its impact on varous philosophical developments. These include the ideas developed by W.V Quine, Thomas Kuhn, Michael Dummett, Bas van Fraassen, and Hilary Puttnam. In each case, Norris argues, these thinkers have been influenced by the orthodox construal of quantum mechanics as requiring drastic revision of principles which had hitherto defined the very nature of scientific method, causal explanati and rational enquiry. Putting the case for a realist approach which adheres to well-tried scientific principles of causal reasoning and inference to the best explanation, Christopher Norris clarifies these debates to a non-specialist readership and scholars of philosophy, science studies and the philosophy of science alike. Quantum Theory and the Flight From Realism suggests that philosophical reflection can contribute to a better understanding of these crucial, current issues. (shrink)

In June 1998 Hans Primas turned 70 y ears old. Although he himself is not fond of jubilees and although he lik es to play the decimal system of numb ers do wn as contingent, this is nev ertheless a suitable o ccasion to re ect on the professional work of one of the rare distinguished contemp orary scientists who attach equal imp ortance to exp erimen tal and theoretical and conceptual lines of researc h. Hans Primas' in terests ha (...) ve covered an enormous range: metho ds and instruments for n uclear magnetic resonance, theoretical c hemistry , C - and W -algebraic formulations of quantum mechanics, the measurement problem and its various implications, holism and realism in quantum theory , theory reduction, the w ork and p ersonality of Wolfgang Pauli, as well as Jungian psychology . In man y of these elds he provided imp ortan t and original fo o d for though t, in some cases going far b eyond the ev eryda y business in the scientic world. As is the case with other scien tists who are conceptually innov ativ e, Hans Primas is read more than he is quoted. His in uence is due to his writings. Even with the current ood of publications, he still p erforms the miracle of ha ving scientists eagerly a waiting his next publication. His external life, by wa y of contrast, is not very sp ectacular. With the exception of a brief p erio d as a guest professor at Washington Univ ersity at St. Louis, he has never b een a wa y from Zuric h for an y length of time. He has nev er b een a warded an y prizes, nev er organized a congress, nev er done any organizational work in a scientic so ciety . He delib erately distanced himself from the hustle and bustle of national and in ternational scien tic business. (shrink)

In a recent paper [e-print quant-ph/0101012], Hardy has given a derivation of “quantum theory from five reasonable axioms.” Here we show that Hardy's first axiom, which identifies probability with limiting frequency in an ensemble, is not necessary for his derivation. By reformulating Hardy's assumptions, and modifying a part of his proof, in terms of Bayesian probabilities, we show that his work can be easily reconciled with a Bayesian interpretation of quantum probability.

In response to recent suggestions that the phenomena of consciousness may be related to those described by quantum theory, it is argued that distinctive features of brain activity are more typical of nonlinear classical dynamics than of quantum dynamics, which is a linear theory. Thus natural scientists should turn to hierarchies of nonlinear classical systems rather than quantum theory for explanations of the brain's mysterious behaviour.

This conference was devoted to the 80 years of the Copenhagen Interpretation, and to the question of the relevance of the Copenhagen interpretation for the present understanding of quantum mechanics. It is in this framework that fundamental questions raised by quantum mechanics, especially in information theory, were discussed throughout the conference. As has become customary in our series of conference in Växjö, we were glad to welcome a fruitful assembly of theoretical physicists, experimentalists, mathematicians and even philosophers (...) interested in the foundations of probability and physics. The nature of quantum fluctuations---in the form of Stochastic Electrodynamics or in other approaches to stochastic quantum mechanics---was also a central topic discussed during the conference, especially during debates. We should also mention talks on the completeness or incompleteness of quantum mechanics; on macroscopic quantum systems; on Bell's inequality, entanglement and experiments on quantum nonlocality (and locality); on Bohmian mechanics; on the connection between quantum mechanics and general relativity; on quantum probability; on quantum computing, quantum teleportation and quantum cryptography technologies; and more generally on the mathematical formalism of quantum mechanics and on the philosophical problems raised by its interpretations. (shrink)

I offer an account of how the quantum theory we have helps us explain so much. The account depends on a pragmatist interpretation of the theory: this takes a quantum state to serve as a source of sound advice to physically situated agents on the content and appropriate degree of belief about matters concerning which they are currently inevitably ignorant. The general account of how to use quantum states and probabilities to explain otherwise puzzling regularities (...) is then illustrated by showing how we can explain single-particle interference phenomena, the stability of matter, and interference of Bose–Einstein condensates. Finally, I note some open problems and relate this account to alternative approaches to explanation that emphasize the importance of causation, of unification, and of structure. 1 Introduction2 Two Requirements on Explanations in Physics3 What We Can use Quantum Theory to Explain4 The Function of Quantum States and Born Probabilities5 How These Functions Contribute to the Explanatory Task6 Example One: Single-Particle Interference7 Example Two: Explanation of the Stability of Matter8 Example Three: Bose Condensation9 Conclusion. (shrink)

Quantum theory is one of science's most thrilling, challenging and even mysterious areas. Scientists such as Planck, Einstein, Bohr, Heisenberg and Schrödinger uncovered bizarre paradoxes in the early 20th century that seemed to destroy the fundamental assumptions of 'classical physics' - the basic laws we are taught in school. Notoriously difficult, quantum theory is nonetheless an amazing and inspiring intellectual adventure, explained here with patience, wit and clarity.

Quantum Theory and the Schism in Physics is one of the three volumes of Karl Popper’s Postscript to the Logic of scientific Discovery . The Postscript is the culmination of Popper’s work in the philosophy of physics and a new famous attack on subjectivist approaches to philosophy of science. Quantum Theory and the Schism in Physics is the third volume of the Postscript . It may be read independently, but it also forms part of Popper’s interconnected (...) argument in the Postscript . It presents Popper’s classic statement on quantum physics and offers important insights into his thinking on problems of method within science and physics as a whole. (shrink)

Quantum theory is a tremendously successful physical theory, but nevertheless suffers from two serious problems: the measurement problem and the problem of interpretational underdetermination. The latter, however, is largely overlooked as a genuine problem of its own. Both problems concern the doctrine of realism, but pull, quite curiously, into opposite directions. The measurement problem can be captured such that due to scientific realism about quantum theory common sense anti-realism follows, while theory underdetermination usually counts (...) as an argument against scientific realism. I will also consider the more refined distinctions of ontic and epistemic realism and demonstrate that quantum theory in its most viable interpretations conflicts with at least one of the various realism claims. A way out of the conundrum is to come to the bold conclusion that quantum theory is, possibly, wrong (in the realist sense). (shrink)

We show that three fundamental information-theoretic constraints -- the impossibility of superluminal information transfer between two physical systems by performing measurements on one of them, the impossibility of broadcasting the information contained in an unknown physical state, and the impossibility of unconditionally secure bit commitment -- suffice to entail that the observables and state space of a physical theory are quantum-mechanical. We demonstrate the converse derivation in part, and consider the implications of alternative answers to a remaining open (...) question about nonlocality and bit commitment. (shrink)

Three recent arguments seek to show that the universal applicability of unitary quantum theory is inconsistent with the assumption that a well-conducted measurement always has a definite physical outcome. In this paper I restate and analyze these arguments. The import of the first two is diminished by their dependence on assumptions about the outcomes of counterfactual measurements. But the third argument establishes its intended conclusion. Even if every well-conducted quantum measurement we ever make will have a definite (...) physical outcome, this argument should make us reconsider the objectivity of that outcome. (shrink)

Philosophers of quantum mechanics have generally addressed exceedingly simple systems. Laura Ruetsche offers a much-needed study of the interpretation of more complicated systems, and an underexplored family of physical theories, such as quantum field theory and quantum statistical mechanics, showing why they repay philosophical attention. She guides those familiar with the philosophy of ordinary QM into the philosophy of 'QM infinity', by presenting accessible introductions to relevant technical notions and the foundational questions they frame--and then develops (...) and defends answers to some of those questions. Finally, Ruetsche highlights ties between the foundational investigation of QM infinity and philosophy more broadly construed, in particular by using the interpretive problems discussed to motivate new ways to think about the nature of physical possibility and the problem of scientific realism. (shrink)

In his recent book Bananaworld. Quantum mechanics for primates, Jeff Bub revives and provides a mature version of his influential information-theoretic interpretation of Quantum Theory (QT). In this paper, I test Bub’s conjecture that QT should be interpreted as a theory about information, by examining whether his information-theoretic interpretation has the resources to explain (or explain away) quantum conundrums. The discussion of Bub’s theses will also serve to investigate, more in general, whether other approaches succeed (...) in defending the claim that QT is about quantum information. First of all, I argue that Bub’s interpretation of QT as a principle theory fails to fully explain quantum non-locality. Secondly, I argue that a constructive interpretation, where the quantum state is interpreted ontically as information, also fails at providing a full explanation of quantum correlations. Finally, while epistemic interpretations might succeed in this respect, I argue that such a success comes at the price of rejecting some in between the most basic scientific standards of physical theories. (shrink)

We present a discrete model theory similar in structure to ordinary quantum mechanics, but based on a finite field instead of complex amplitudes. The interpretation of this theory involves only the “modal” concepts of possibility and necessity rather than quantitative probability measures. Despite its simplicity, our model theory includes entangled states and has versions of both Bell’s theorem and the no cloning theorem.

The measurement problem of quantum theory is discussed, and the difficulty of trying to solve it within the confines of a local, Lorentz-invariant physics is emphasised. This leads to the obvious suggestion to seek a solution beyond physics, in particular, by introducing the concept of consciousness. The resulting dualistic model, in the natural form suggested by quantum theory, is shown to differ in several respects from the classical model of Descartes, and to suggest solutions to some (...) of the long-standing problems concerning the relation of consciousness to the physical world. (shrink)

The aim of the paper is to demonstratethat Special Relativity and the Early Quantum Theory were created within the same programme of statisticalmechanics, thermodynamics and maxwellianelectrodynamics reconciliation. I shall try to explainwhy classical mechanics and classicalelectrodynamics were ``refuted'''' almost simultaneouslyor, in more suitable terms for the present congress,why did the quantum revolution and the relativisticone both took place at the beginning of the 20-thcentury. I shall argue that the quantum andrelativistic revolutions were simultaneous since theyhad a (...) common origin -- the clash between thefundamental theories of the second half of the 19-thcentury that constituted the ``body'''' of ClassicalPhysics. The revolution''s most dramatic pointwas Einstein''s 1905 photon paper that laid thefoundations of both Special Relativity and OldQuantum Theory. Hence the dialectic of the oldtheories is crucial for theory change. Modern physicsbegan with Einstein''s reconciliation ofelectrodynamics, mechanics and thermodynamics in 1905and his unification of Special Relativity andNewtonian Theory of Gravity. Or, in a more generalsocial context: progressive scientific change can bedescribed not in Weberian terms of zweckrationalaction forcing out all the other forms of action onlybut in terms of Habermas''s communicative rationalityencouraging the establishment of mutual understandingbetween the various scientific communities also.Einstein''s programme constituted a progressive stepwith respect to its rivals not because it couldexplain more ``facts'''' or was more ``mathematical''''. Itwas better than its rivals because it constituted abasis of communication and interpenetration betweenthree main paradigms of 19-th century physics. Ofcourse in the long run it resulted in empiricalsuccesses. (shrink)

How do scientists approach science? Scientists, sociologists and philosophers were asked to write on this intriguing problem and to display their results at the International Congress `Einstein Meets Magritte'. The outcome of their effort can be found in this rather unique book, presenting all kinds of different views on science. Quantum mechanics is a discipline which deserves and receives special attention in this book, mainly because it is fascinating and, hence, appeals to the general public. This book not only (...) contains articles on the introductory level, it also provides new insights and bold, even provocative proposals. That way, the reader gets acquainted with `science in the making', sitting in the front row. The contributions have been written for a broad interdisciplinary audience of scholars and students. (shrink)

A sophisticated and original introduction to the philosophy of quantum mechanics from one of the world’s leading philosophers of physics In this book, Tim Maudlin, one of the world’s leading philosophers of physics, offers a sophisticated, original introduction to the philosophy of quantum mechanics. The briefest, clearest, and most refined account of his influential approach to the subject, the book will be invaluable to all students of philosophy and physics. Quantum mechanics holds a unique place in the (...) history of physics. It has produced the most accurate predictions of any scientific theory, but, more astonishing, there has never been any agreement about what the theory implies about physical reality. Maudlin argues that the very term “quantum theory” is a misnomer. A proper physical theory should clearly describe what is there and what it does—yet standard textbooks present quantum mechanics as a predictive recipe in search of a physical theory. In contrast, Maudlin explores three proper theories that recover the quantum predictions: the indeterministic wavefunction collapse theory of Ghirardi, Rimini, and Weber; the deterministic particle theory of deBroglie and Bohm; and the conceptually challenging Many Worlds theory of Everett. Each offers a radically different proposal for the nature of physical reality, but Maudlin shows that none of them are what they are generally taken to be. (shrink)

Physicists and philosophers argue whether quantum theory has spiritual implications. The vast majority of opinions are at two extremes: Some contend that quantum theory has absolutely no spiritual implications whatsoever, whereas others assert that it forms the very basis of a modern spirituality and can be directly applied to the human condition. It is this article's contention that neither extreme is correct. Quantum theory does have spiritual implications - a fact that its founders intuited (...) and its enemies, Einstein preeminent among them, considered prima facie evidence of its as yet undiscovered flaws. Quantum theory has proven itself against all challenges more successfully than any other scientific theory, but its spiritual implications are extremely subtle. It provides a boundary to the materialistic, deterministic worldview and shows that there must be more to reality than that, but is inherently incapable of providing evidence as to the nature of what lies beyond that boundary. (shrink)

This article seeks to clarify the relation between consciousness and quantum physics. It is argued that, in order to be consistent with quantum theory, one must never assert that conscious action has caused a given event to occur. Rather, consciousness must be identified with "measurement" or, more concretely, with an increase in the entropy of the probability distribution of possible events. It is suggested that the feeling of self-awareness may be associated with the exchange of entropy between (...) groups of quantum systems which are so tightly coupled as to be, for all practical purposes, an indivisible unit. Such groups of systems may be understood to measure themselves. Two interpretations of the quantum theory of consciousness are distinguished: one in which consciousness is defined as quantum measurement; and one in which this measurement is hypothesized to correlate with a certain biological phenomenon called consciousness. (shrink)

Although quantum theory is applicable, in principle, to both the microscopic and macroscopic realms, the strategy of practically applying quantum theory by retaining a classical conception of the macroscopic world has had tremendous success. This has nevertheless rendered the task of interpretation daunting. We argue the need for recognizing and solving the ‘observation problem', namely constructing a ‘quantum-compatible’ view of the properties and states of macroscopic objects in everyday thinking to realistically interpret quantum (...) class='Hi'>theory consistently at both the microscopic and macroscopic levels. Toward a solution to this problem, we point out a category of properties called ‘relational properties’ that we regularly associate with everyday objects. We see them as being potentially quantum-compatible. Some possible physical implications are discussed. We conclude by touching upon the nexus between the relational property view within quantum physics and some neurobiological issues underlying cognition. (shrink)

In the present work, quantum theory is founded on the framework of consciousness, in contrast to earlier suggestions that consciousness might be understood starting from quantum theory. The notion of streams of consciousness, usually restricted to conscious beings, is extended to the notion of a Universal/Global stream of conscious flow of ordered events. The streams of conscious events which we experience constitute sub-streams of the Universal stream. Our postulated ontological character of consciousness also consists of an (...) operator which acts on a state of potential consciousness to create or modify the likelihoods for later events to occur and become part of the Universal conscious flow. A generalized process of measurement-perception is introduced, where the operation of consciousness brings into existence, from a state of potentiality, the event in consciousness. This is mathematically represented by (a) an operator acting on the state of potential consciousness before an actual event arises in consciousness and (b) the reflecting of the result of this operation back onto the state of potential consciousness for comparison in order for the event to arise in consciousness. Beginning from our postulated ontology that consciousness is primary and from the most elementary conscious contents, such as perception of periodic change and motion, quantum theory follows naturally as the description of the conscious experience. (shrink)

It is widely accepted that consciousness or, in other words, mental activity is in some way correlated to the behavior of the brain or, in other words, material brain activity. Since quantum theory is the most fundamental theory of matter that is currently available, it is a legitimate question to ask whether quantum theory can help us to understand consciousness. Several approaches answering this question a?rmatively, proposed in recent decades, will be surveyed. It will be (...) pointed out that they make di?erent epistemological assumptions, refer to di?erent neurophysiological levels of description, and adopt quantum theory in di?erent ways. For each of the approaches discussed, these imply both.. (shrink)

Quantum theory does not only predict probabilities, but also relative phases for any experiment, that involves measurements of an ensemble of systems at different moments of time. We argue, that any operational formulation of quantum theory needs an algebra of observables and an object that incorporates the information about relative phases and probabilities. The latter is the (de)coherence functional, introduced by the consistent histories approach to quantum theory. The acceptance of relative phases as a (...) primitive ingredient of any quantum theory, liberates us from the need to use a Hilbert space and non-commutative observables. It is shown, that quantum phenomena are adequately described by a theory of relative phases and non-additive probabilities on the classical phase space. The only difference lies on the type of observables that correspond to sharp measurements. This class of theories does not suffer from the consequences of Bell's theorem (it is not a theory of Kolmogorov probabilities) and Kochen–Specker's theorem (it has distributive “logic”). We discuss its predictability properties, the meaning of the classical limit and attempt to see if it can be experimentally distinguished from standard quantum theory. Our construction is operational and statistical, in the spirit of Copenhagen, but makes plausible the existence of a realist, geometric theory for individual quantum systems. (shrink)

In this paper, we discuss the general significance of order in physics, as a first step toward the development of new notions of order. We begin with a brief historical discussion of the notions of order underlying ancient Greek views, and then go on to show how these changed in key ways with the rise of classical physics. This leads to a broader view of the significance of order, which helps to indicate what is to be meant by a change (...) of our general notions of order in physics. We then go into relativity and quantum theory, showing how these developments actually did bring in further new notions of order, which are however inconsistent and otherwise inadequate in certain ways. Finally, using these inconsistencies and inadequacies as clues or indications for yet a further new concept of order, we make some proposals for novel directions of inquiry (to be discussed in some detail in later papers) which could lead to theories as different from relativity and quantum theory as these are from classical physics. (shrink)