
180Probability, arrow of time and decoherenceStudies in History and Philosophy of Modern Physics 38 (2): 439456. 2006.This paper relates both to the metaphysics of probability and to the physics of time asymmetry. Using the formalism of decoherent histories, it investigates whether intuitions about intrinsic time directedness that are often associated with probability can be justified in the context of nocollapse approaches to quantum mechanics. The standard approach to time symmetry in the decoherent histories literature is criticised, and an alternative approach is proposed, based on two decoherence conditio…Read more

167Insolubility Theorems and EPR ArgumentEuropean Journal for Philosophy of Science 3 (1): 87100. 2013.I present a very general and simple argument—based on the nosignalling theorem—showing that within the framework of the unitary Schrödinger equation it is impossible to reproduce the phenomenological description of quantum mechanical measurements (in particular the collapse of the state of the measured system) by assuming a suitable mixed initial state of the apparatus. The thrust of the argument is thus similar to that of the ‘insolubility theorems’ for the measurement problem of quantum mecha…Read more

148The philosophical debate about quantum logic between the late 1960s and the early 1980s was generated mainly by Putnam's claims that quantum mechanics empirically motivates introducing a new form of logic, that such an empirically founded quantum logic is the `true' logic, and that adopting quantum logic would resolve all the paradoxes of quantum mechanics. Most of that debate focussed on the latter claim, reaching the conclusion that it was mistaken. This chapter will attempt to clarify the pos…Read more

127Heisenberg (and Schrödinger, and Pauli) on hidden variablesStudies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 40 (4): 374382. 2009.In this paper, we discuss various aspects of Heisenberg’s thought on hidden variables in the period 1927–1935. We also compare Heisenberg’s approach to others current at the time, specifically that embodied by von Neumann’s impossibility proof, but also views expressed mainly in correspondence by Pauli and by Schroedinger. We shall base ourselves mostly on published and unpublished materials that are known but littlestudied, among others Heisenberg’s own draft response to the EPR paper. Our aim…Read more

72Remarks on Spacetime and Locality in Everett's InterpretationIn T. Placek & J. Butterfield (eds.), NonLocality and Modality, Kluwer Academic Publishers. pp. 105122. 2001.Interpretations that follow Everett's idea that the universal wave function contains a multiplicity of coexisting realities, usually claim to give a completely local account of quantum mechanics. That is, they claim to give an account that avoids both a nonlocal collapse of the wave function, and the action at a distance needed in hidden variable theories in order to reproduce the quantum mechanical violation of the Bell inequalities. In this paper, I sketch how these claims can be substantiate…Read more

70The role of decoherence in quantum mechanicsStanford Encyclopedia of Philosophy. 2003.Interference phenomena are a wellknown and crucial feature of quantum mechanics, the twoslit experiment providing a standard example. There are situations, however, in which interference effects are (artificially or spontaneously) suppressed. We shall need to make precise what this means, but the theory of decoherence is the study of (spontaneous) interactions between a system and its environment that lead to such suppression of interference. This study includes detailed modelling of systemen…Read more

62Definitions of time symmetry and examples of timedirected behaviour are discussed in the framework of discrete Markov processes. It is argued that typical examples of timedirected behaviour can be described using timesymmetric transition probabilities. Some current arguments in favour of a distinction between past and future on the basis of probabilistic considerations are thereby judged to be unjustified.

62Modal interpretations, decoherence and measurementsStudies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 27 (3): 239277. 1996.

55The publication of the EPR paper in 1935 prompted Heisenberg to draft a manuscript on the question of the completability of quantum mechanics. We give here the English translation of this manuscript with a brief introduction and bibliography.

52The topic of probabilty in quantum mechanics is rather vast, and in this article, we shall choose to discuss it from the perspective of whether and in what sense quantum mechanics requires a generalisation of the usual concept of probability. We shall focus on the case of finitedimensional quantum mechanics, partly for simplicity and partly for ease of generalisation. While we shall largely focus on formal aspects of quantum probability, our discussion will relate also to notorious issues in th…Read more

45Nelson’s programme for a stochastic mechanics aims to derive the wave function and the Schroedinger equation from natural conditions on a diffusion process in configuration space. If successful, this pro gramme might have some advantages over the betterknown determin istic pilotwave theory of de Broglie and Bohm. The essential points of Nelson’s strategy are reviewed, with particular emphasis on concep tual issues relating to the role of time symmetry. The main problem in Nelson’s approach …Read more

43This is an Essay Review of "Many Worlds? Everett, Quantum Theory, & Reality", edited by Simon Saunders, Jonathan Barrett, Adrian Kent, and David Wallace. A much shortened version of this review is appearing in "Metascience" under the title "The Many Facets of Everett’s Many Worlds".

41A concrete procedure for obtaining sharp reconstructions of unsharp observables in finitedimensional quantum mechanicsFoundations of Physics 27 (10): 13231343. 1997.We discuss the problem of how a (commutative) generalized observable in a finitedimensional Hilbert space (communtative effectvalued resolution of the identity) can be considered as an unsharp realization of some standard observable (projectionvalued resolution of the identity). In particular, we give a concrete procedure for constructing such a standard observable. Some results about the “uniqueness” of the resulting observable are also examined

40Making Sense of Approximate DecoherencePSA: Proceedings of the Biennial Meeting of the Philosophy of Science Association 1994. 1994.In realistic situations where a macroscopic system interacts with an external environment, decoherence of the quantum state, as derived in the decoherence approach, is only approximate. We argue that this can still give rise to facts, provided that during the decoherence process states that are, respectively, always close to eigenvectors of pointer position and record observable are correlated. We show in a model that this is always the case.

39Collapse theories as beable theoriesManuscrito 33 (1): 1954. 2010.I discuss the interpretation of spontaneous collapse theories, with particular reference to Bell's suggestion that the stochastic jumps in the evolution of the wave function should be considered as local beables of the theory. I develop this analogy in some detail for the case of nonrelativistic GRWtype theories, using a generalisation of Bell's notion of beables to POV measures. In the context of CSLtype theories, this strategy appears to fail, and I discuss instead Ghirardi and coworkers' …Read more

38In 1935, Einstein, Podolsky and Rosen famously published a paper arguing for the incompleteness of quantum mechanics, using the example of two spatially separated but entangled particles. In his almost equally famous reply, Niels Bohr argued against EPR by providing a careful analysis of quantum measurements from the point of view of complementarity. Perhaps oddly, this analysis focuses on the example of a *single* particle passing through a slit. In this paper I argue that the disanalogy betwee…Read more

38We review and discuss the recent monograph by David Wallace on Everettian Quantum Mechanics. This book is a high point of two decades of work on Everett in both physics and philosophy. It is also a beautiful and welcome exemplar of a modern way of doing metaphysics. We discuss certain aspects more critically, and take the opportunity to sketch an alternative pragmatist approach to probability in Everett, to be fully developed elsewhere.

38Quantum Theory at the Crossroads: Reconsidering the 1927 Solvay ConferenceCambridge University Press. 2009.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 pilotwave theory, Born and Heisenberg's quantum mechanics, and Schrödinger's wave mechanics. Today, there is no longer an established or dominant interpretat…Read more

37Delocalized Properties in the Modal Interpretation of a Continuous Model of DecoherenceFoundations of Physics 30 (9): 14311444. 2000.I investigate the character of the definite properties defined by the Basic Rule in the Vermaas and Dieks' (1995) version of the modal interpretation of quantum mechanics, specifically for the case of the continuous model of decoherence by Joos and Zeh (1985). While this model suggests that the characteristic length that might be associated with the localisation of an individual system is the coherence length of the state (which converges rapidly to the thermal de Broglie wavelength), I show in …Read more

37In a recent paper, I have analysed and criticised Leggett and Garg’s argument to the effect that macroscopic realism contradicts quantum mechanics, by contrasting their assumptions to the example of Bell’s stochastic pilotwave theories, and have applied Dzhafarov and Kujala’s analysis of contextuality in the presence of signalling to the case of the Leggett–Garg inequalities. In this chapter, I discuss more in general the motivations for macroscopic realism, taking a cue from Einstein’s critici…Read more

34Review of The Emergent MultiverseDavid Wallace, The Emergent Multiverse: Quantum Theory according to the Everett Interpretation. Oxford: Oxford University Press , xvi+530 pp., $75.00 (review)Philosophy of Science 82 (1): 129148. 2015.

31Neither geometric phases nor differences in geometric phases are generally invariant under timedependent unitary transformations (unlike differences in total phases), in particular under local gauge transformations and Galilei transformations. (This was pointed out originally by Aharonov and Anandan, and in the case of Galilei transformations has recently been shown explicitly by Sjoeqvist, Brown and Carlsen.) In this paper, I introduce a phase, related to the standard geometric phase, for whic…Read more

30Locality and Mentality in Everett Interpretations: Albert and Loewer’s Many MindsMind and Matter 11 (2). 2013.This is the first of two papers reviewing and analysing the approach to locality and to mindbody dualism proposed in Everett interpreta tions of quantum mechanics. The planned companion paper will focus on the contemporary decoherencebased approaches to Everett. This paper instead treats the explicitly mentalistic Many Minds Interpreta tion proposed by David Albert and Barry Loewer (Albert and Loewer 1988). In particular, we investigate what kind of supervenience of the mind on the body is i…Read more

25Dynamics for Modal InterpretationsFoundations of Physics 29 (8): 11651201. 1999.An outstanding problem in socalled modal interpretations of quantum mechanics has been the specification of a dynamics for the properties introduced in such interpretations. We develop a general framework (in the context of the theory of stochastic processes) for specifying a dynamics for interpretations in this class, focusing on the modal interpretation by Vermaas and Dieks. This framework admits many empirically equivalent dynamics. We give some examples, and discuss some of the properties o…Read more

21This article focuses on two of the main problems raising interpretational issues in quantum mechanics, namely the notorious measurement problem and the equally important but not quite as widely discussed problem of the classical regime. The two problems are distinct, but they are both intimately related to some of the issues arising from entanglement and density operators. The article aims to be fairly nontechnical in language, but modern in outlook and covering the chosen topics in more depth …Read more

21This is a review of Barrett and Byrne's commented edition of Everett's collected works, originally published in HOPOS 3, 348352, but here including footnotes and references.

21This paper comments on a paper by Chris Fuchs. Both papers are to appear in "New Directions in the Philosophy of Science", eds. M. C. Galavotti, S. Hartmann, M. Weber, W. Gonzalez, D. Dieks and T. Uebel. This paper presents some mild criticisms of Fuchs's views, some based on the EPR and Wigner's friend scenarios, and some based on the quantum theory of measurement. A few alternative suggestions for implementing a subjectivist interpretation of probability in quantum mechanics conclude the paper…Read more

21The symmetries of the wavefunction for identical particles, including anyons, are given a rigorous nonrelativistic generalisation within pilotwave formulations of quantum mechanics. In particular, parastatistics are excluded. The result has a rigorous generalisation to _n_ particles and to spinorial wavefunctions. The relation to other nonrelativistic approaches is briefly discussed.
Utrecht, Utrecht, Netherlands
Areas of Specialization
Philosophy of Physical Science 
Areas of Interest
Philosophy of Physical Science 
Philosophy of Probability 