•  258
    Jill North argues that Hamiltonian mechanics provides the most spare -- and hence most accurate -- account of the structure of a classical world. We point out some difficulties for her argument, and raise some general points about attempts to minimize structural commitments
  •  158
    On the Ostrogradski Instability; or, Why Physics Really Uses Second Derivatives
    British Journal for the Philosophy of Science 73 (1): 23-46. 2022.
    Candidates for fundamental physical laws rarely, if ever, employ higher than second time derivatives. Easwaran sketches an enticing story that purports to explain away this puzzling fact and thereby provides indirect evidence for a particular set of metaphysical theses used in the explanation. I object to both the scope and coherence of Easwaran's account, before going on to defend an alternative, more metaphysically deflationary explanation: in interacting Lagrangian field theories, it is eithe…Read more
  •  136
    How to Be a Relativistic Spacetime State Realist
    British Journal for the Philosophy of Science 71 (3): 933-957. 2018.
    According to spacetime state realism, the fundamental ontology of a quantum mechanical world consists of a state-valued field evolving in four-dimensional spacetime. One chief advantage it claims over rival wave-function realist views is its natural compatibility with relativistic quantum field theory. I argue that the original density operator formulation of SSR cannot be extended to QFTs where the local observables form type III von Neumann algebras. Instead, I propose a new formulation of SSR…Read more
  •  135
    The Conventionality of Parastatistics
    British Journal for the Philosophy of Science 66 (4): 929-976. 2015.
    Nature seems to be such that we can describe it accurately with quantum theories of bosons and fermions alone, without resort to parastatistics. This has been seen as a deep mystery: paraparticles make perfect physical sense, so why don’t we see them in nature? We consider one potential answer: every paraparticle theory is physically equivalent to some theory of bosons or fermions, making the absence of paraparticles in our theories a matter of convention rather than a mysterious empirical disco…Read more
  •  114
    A major obstacle facing interpreters of quantum field theory is a proliferation of different theoretical frameworks. This article surveys three of the main available options—Lagrangian, Wightman, and algebraic QFT—and examines how they are related. Although each framework emphasizes different aspects of QFT, leading to distinct strengths and weaknesses, there is less tension between them than commonly assumed. Given the limitations of our current knowledge and the need for creative new ideas, I …Read more
  •  112
    Can Quantum Thermodynamics Save Time?
    Philosophy of Science 88 (2): 281-302. 2021.
    The thermal time hypothesis is a proposed solution to the problem of time: a coarse-grained state determines a thermal dynamics according to which it is in equilibrium, and this defines the f...
  •  89
    Deciphering the algebraic CPT theorem
    Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 68 106-125. 2019.
    The CPT theorem states that any causal, Lorentz-invariant, thermodynamically well-behaved quantum field theory must also be invariant under a reflection symmetry that reverses the direction of time, flips spatial parity, and conjugates charge. Although its physical basis remains obscure, CPT symmetry appears to be necessary in order to unify quantum mechanics with relativity. This paper attempts to decipher the physical reasoning behind proofs of the CPT theorem in algebraic quantum field theory…Read more
  •  10
    Relativistic quantum field theory (QFT) is ostensibly a quantum mechanical theory of fields, but determining exactly what these are is a thorny metaphysical task in the face of no-go arguments given by Baker (2009). This paper explores three possible answers according to which quantum fields are (I) superpositions of classical fields, (II) fields of expectation values for local observables, or (III) fields of local quantum states. I argue that each of these ontologies has resources available to …Read more