A puzzle concerning local symmetries and their empirical significance, The British Journal for the Philosophy of Science (forthcoming)
In the last five years, the controversy about whether or not gauge transformations can be empirically significant has intensified. On the one hand, Greaves and Wallace (2014) developed a framework according to which, under some circumstances, gauge transformations can be empirically significant—and Teh (2015) further supported this result by using the Constrained Hamiltonian formalism. On the other hand, Friederich (2015, 2016) claims to have proved that gauge transformation can never be empirically significant. In this paper, I accomplish two tasks. First, I argue that there are strong reasons to resist Friederich’s proof because one of its assumptions is, at the very least, highly controversial. Second, I argue that, despite criticism by Brading and Brown (2004) and Friederich (2015), ‘t Hooft’s Beam-Splitter experiment is indeed a concrete example of a case where a local gauge symmetry has empirical significance. By shedding light on these two points, this paper shows that recent arguments that claim gauge transformations cannot be empirically significant are not satisfactory.
Abandoning Galileo’s Ship: The quest for non-relational empirical significance (with Nicholas Teh), The British Journal for the Philosophy of Science (forthcoming)
The recent debate about whether gauge symmetries can be empirically significant has focused on the possibility of ‘Galileo’s ship’ types of scenarios, where the symmetries effect relational differences between a subsystem and the environment. However, it has gone largely unremarked that apart from such Galileo’s ship scenarios, Greaves and Wallace (2014) proposed that gauge transformations can also be empirically significant in a ‘non-relational’ manner that is analogous to a Faraday-cage scenario, where the subsystem symmetry is related to a change in a charged boundary state. In this paper, we investigate the question of whether such non-relational scenarios are possible for gauge theories. Remarkably, the answer to this question turns out to be closely related to a foundational puzzle that has driven a host of recent developments at the frontiers of theoretical physics. By drawing on these recent developments, we show that a very natural way of elaborating on Greaves and Wallace’s claim of non-relational empirical significance for gauge symmetry is incoherent. However, we also argue that much of what they suggest is correct in spirit: one can indeed construct non-relational models of the kind they sketch, albeit ones where the empirical significance is not witnessed by a gauge symmetry but instead by a superficially similar boundary symmetry. Furthermore, the latter casts doubt on whether one really abandons Galileo’s ship in such scenarios.
One Hundred years of general relativity (with Katherine Brading and Laura Wells), in Metascience
Papers Under Review
Separating Einstein’s Separability
In this paper, I accomplish a primarily conceptual task and a historical task. The conceptual task is to argue that (1) Einstein’s Principle of Separability (henceforth “separability”) is not a supervenience principle and that (2) separability and entanglement are compatible. I support (1) by showing that the conclusion of Einstein’s incompleteness argument would still follow even if one assumes that the state of a composite system does not supervene on the states of the subsystems, and by showing that what Einstein says in “Quantum Mechanics and Reality” (1948) strongly suggests that separability is not a principle about how subsystem states relate to the state of composite systems. I support (2) by showing that if separability was incompatible with entanglement, then Einstein’s argument would be incoherent in a trivial way. The historical task is to offer the first detailed review of the different ways in which separability has been defined by physicists and philosophers in the last 60 years. Among other things, such a review distinguishes three different definitions of the principle, and shows that since the 1990s and up until the present date, it became standard to take separability (as presented by Einstein) to be a supervenience principle. Thus, by arguing for (1) and (2) I directly challenge what has been, and still is, a very common reading of separability.
On Measuring Absolute Velocity (with Ben Middleton)
We defend a negative thesis and a positive one. The negative thesis is that the standard argument for the thesis that absolute velocity is not measurable in newtonian worlds fails. In particular, we show that both the simpler version of the argument and the most sophisticated one (due to Roberts (2008)) fail because they each depend on a criterion of measurement so demanding that it does not apply to the measurements found in actual science. The positive thesis is that, under an alternative and more adequate criterion of measurement, there are indeed newtonian worlds in which absolute velocity is measured. These newtonian worlds are counterexamples to the widely endorsed thesis that if a property fails to be invariant under the symmetries of a theory, then, according to that theory, the property could not be measured.