The task of quantizing general relativity raises serious questions about the meaning of the present formulation and interpretation of quantum mechanics when applied to so fundamental a structure as the space-time geometry itself. This paper seeks to clarify the foundations of quantum mechanics. It presents a reformulation of quantum theory in a form believed suitable for application to general relativity. The aim is not to deny or contradict the conventional formulation of quantum theory, which has demonstrated its usefulness in an overwhelming variety of problems, but rather to supply a new, more general and complete formulation, from which the conventional interpretation can be deduced. The relationship of this new formulation to the older formulation is therefore that of a metatheory to a theory, that is, it is an underlying theory in which the nature and consistency, as well as the realm of applicability, of the older theory can be investigated and clarified.

"relative State" Formulation of Quantum Mechanics

Quantum mechanics is an extremely successful theory that agrees with every experimental test. However, the principle of linear superposition, a central tenet of the theory, apparently contradicts a commonplace observation: macroscopic objects are never found in a linear superposition of position states. Moreover, the theory does not explain why during a quantum measurement, deterministic evolution is replaced by probabilistic evolution, whose random outcomes obey the Born probability rule. In this article a review is given of an experimentally falsifiable phenomenological proposal, known as continuous spontaneous collapse: a stochastic nonlinear modification of the Schr\"odinger equation, which resolves these problems, while giving the same experimental results as quantum theory in the microscopic regime. Two underlying theories for this phenomenology are reviewed: trace dynamics and gravity-induced collapse. As the macroscopic scale is approached, predictions of this proposal begin to differ appreciably from those of quantum theory and are being confronted by ongoing laboratory experiments that include molecular interferometry and optomechanics. These experiments, which test the validity of linear superposition for large systems, are reviewed here, and their technical challenges, current results, and future prospects summarized. It is likely that over the next two decades or so, these experiments can verify or rule out the proposed stochastic modification of quantum theory.

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Models of Wave-function Collapse, Underlying Theories, and Experimental Tests

The Quark and the Jaguar

A partir d'une analyse des aspects philosophiques et ideologiques de la mecanique quantique et de la relativite generale, l'A. etudie le developpement scientifique que constitue l'emergence des nouvelles theories de la gravite quantique et en mesure les consequences culturelles et politiques

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Transgressing the Boundaries: Toward a Transformative Hermeneutics of Quantum Gravity

Much of our understanding of human thinking is based on probabilistic models. This innovative book by Jerome R. Busemeyer and Peter D. Bruza argues that, actually, the underlying mathematical structures from quantum theory provide a much better account of human thinking than traditional models. They introduce the foundations for modelling probabilistic-dynamic systems using two aspects of quantum theory. The first, 'contextuality', is a way to understand interference effects found with inferences and decisions under conditions of uncertainty. The second, 'quantum entanglement', allows cognitive phenomena to be modeled in non-reductionist ways. Employing these principles drawn from quantum theory allows us to view human cognition and decision in a totally new light. Introducing the basic principles in an easy-to-follow way, this book does not assume a physics background or a quantum brain and comes complete with a tutorial and fully worked-out applications in important areas of cognition and decision.

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Quantum Models of Cognition and Decision

Introduction 1. A Modest Proposal Concerning Laws, Counterfacutals, and Explanations 2. Why Be Humean 3. Suggestions Form Physics For Deep Metaphysics 4. On the Passing of Time 5. Causation, Counterfactuals, and the Third Factor 6. The Whole Ball of Wax Epilogue: A Remark on the Method of Metaphysics

The Metaphysics Within Physics

It is sometimes stated that composite quantum systems in entangled states are fundamentally ‘non-local’(i.e. a measurement on one component system can affect a spacelike separated system ‘instantaneously’) and therefore, non-relativistic quantum mechanics violates Relativity theory. This conclusion is usually thought to follow directly from Bell's Theorem in quantum mechanics and the upper limit on velocities provided by the speed of light in Relativity. But exactly what if the conflict between the kind of non-locality exhibited by entangled quantum systems and either the Special or General Theory of Relativity? Maudlin's Quantum Non-Locality and Relativity is a beautifully crafted book that attempts to answer this question by evaluating four purported restrictions imposed by Relativity. He also considers four attempts to formulate Lorentz invariant quantum theories and concludes that such accounts exact a high philosophical price. Maudlin has achieved his first goal: he gives a lucid exposition of the tension between quantum non-locality and Relativity theory which is accessible to the non-specialist. But is there a high philosophical price to be paid for Lorentz invariant quantum theories and can we afford it?

Quantum non-locality and relativity

Preface to First Edition vi Preface to Second Edition x Preface to Third Edition xii Introduction 1 1 Bell s Theorem: The Price of Locality 6 Appendix A: The GHZ Scheme 24 2 Relativity and Space-time Structure 27 3 Finger Exercise: Superluminal Matter Transport 55 4 Controlling the Connection: Signals 74 Appendix B: Bohmian Mechanics 106 5 Causation 114 6 Secret Messages 148 7 Points of View 173 8 Life in Elastic Space-time 205 9 Morals 221 10 New Discoveries and Deeper Insights: The View from 2010 224 An Overview of Quantum Mechanics 260 References 284 Index 290

Quantum non-locality and relativity : metaphysical intimations of modern physics

The aim of this essay is to distinguish and analyze several difficulties confronting attempts to reconcile the fundamental quantum mechanical dynamics with Born's rule. It is shown that many of the proposed accounts of measurement fail at least one of the problems. In particular, only collapse theories and hidden variables theories have a chance of succeeding, and, of the latter, the modal interpretations fail. Any real solution demands new physics.

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Tim Maudlin

Papers

The Metaphysics Within Physics

Quantum non-locality and relativity

Quantum non-locality and relativity : metaphysical intimations of modern physics

Three Measurement Problems

Philosophy of Physics: Space and Time