•  290
    Symmetries and Paraparticles as a Motivation for Structuralism
    British Journal for the Philosophy of Science 63 (2): 233-285. 2012.
    This article develops an analogy proposed by Stachel between general relativity (GR) and quantum mechanics (QM) as regards permutation invariance. Our main idea is to overcome Pooley's criticism of the analogy by appeal to paraparticles. In GR, the equations are (the solution space is) invariant under diffeomorphisms permuting spacetime points. Similarly, in QM the equations are invariant under particle permutations. Stachel argued that this feature—a theory's ‘not caring which point, or particl…Read more
  •  746
    Causal Decision Theory and EPR correlations
    with Arif Ahmed
    Synthese 191 (18): 4315-4352. 2014.
    The paper argues that on three out of eight possible hypotheses about the EPR experiment we can construct novel and realistic decision problems on which (a) Causal Decision Theory and Evidential Decision Theory conflict (b) Causal Decision Theory and the EPR statistics conflict. We infer that anyone who fully accepts any of these three hypotheses has strong reasons to reject Causal Decision Theory. Finally, we extend the original construction to show that anyone who gives any of the three hypoth…Read more
  •  255
    On Kinds of Indiscernibility in Logic and Metaphysics
    British Journal for the Philosophy of Science 63 (1): 27-84. 2012.
    Using the Hilbert-Bernays account as a spring-board, we first define four ways in which two objects can be discerned from one another, using the non-logical vocabulary of the language concerned. Because of our use of the Hilbert-Bernays account, these definitions are in terms of the syntax of the language. But we also relate our definitions to the idea of permutations on the domain of quantification, and their being symmetries. These relations turn out to be subtle---some natural conjectures abo…Read more
  •  46
    The purpose of this short article is to build on the work of Ghirardi, Marinatto and Weber and Ladyman, Linnebo and Bigaj, in supporting a redefinition of en- tanglement for “indistinguishable” systems, particularly fermions. According to the proposal, non-separability of the joint state is insufficient for entanglement. The re- definition is justified by its physical significance, as enshrined in three biconditionals whose analogues hold of “distinguishable” systems.
  •  51
    In this article I expound an understanding of the quantum mechanics of so-called “indistinguishable” systems in which permutation invariance is taken as a symmetry of a special kind, namely the result of representational redundancy. This understand- ing has heterodox consequences for the understanding of the states of constituent systems in an assembly and for the notion of entanglement. It corrects widespread misconceptions about the inter-theoretic relations between quantum mechanics and both …Read more
  •  142
    Discerning “Indistinguishable” Quantum Systems
    Philosophy of Science 80 (1): 49-72. 2013.
    In a series of recent papers, Simon Saunders, Fred Muller, and Michael Seevinck have collectively argued, against the folklore, that some nontrivial version of Leibniz’s principle of the identity of indiscernibles is upheld in quantum mechanics. They argue that all particles—fermions, paraparticles, anyons, even bosons—may be weakly discerned by some physical relation. Here I show that their arguments make illegitimate appeal to nonsymmetric, that is, permutation-noninvariant, quantities and tha…Read more
  •  136
    The role of symmetry in the interpretation of physical theories
    Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 52 (Part B): 153-162. 2015.
    The symmetries of a physical theory are often associated with two things: conservation laws and representational redundancies. But how can a physical theory's symmetries give rise to interesting conservation laws, if symmetries are transformations that correspond to no genuine physical difference? In this article, I argue for a disambiguation in the notion of symmetry. The central distinction is between what I call "analytic" and "synthetic" symmetries, so called because of an analogy with analy…Read more
  •  84
    Is mereology empirical? : composition for fermions
    In Tomasz Bigaj & Christian Wüthrich (eds.), Metaphysics in Contemporary Physics, Brill | Rodopi. 2015.
    How best to think about quantum systems under permutation invariance is a question that has received a great deal of attention in the literature. But very little attention has been paid to taking seriously the proposal that permutation invariance reflects a representational redundancy in the formalism. Under such a proposal, it is far from obvious how a constituent quantum system is represented. Consequently, it is also far from obvious how quantum systems compose to form assemblies, i.e. what i…Read more