Heidelberg 2022 – wissenschaftliches Programm

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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 7: Symmetries and Principles

AGPhil 7.1: Hauptvortrag

Mittwoch, 23. März 2022, 16:15–17:00, AGPhil-H14

On an inferential role of spacetime in particle physics — •Tushar Menon — Faculty of Philosophy, University of Cambridge, Sidgwick Avenue, Cambridge CB3 9DA

Here is a plausible claim from particle physics: the states in a gauge multiplet correspond to (possibly distinct) configurations of the same type of particle. Take, for example, the spin-up and spin-down states (with respect to some axis) of an electron in an SU(2) multiplet. But surely, one might worry, not all such formal unifications count. Consider an electron-neutrino doublet, which is also an SU(2) multiplet. It seems less straightforward (or correct!) to consider these two be two states of the same type of particle. But why?

Consider what we might call the Redhead-Weingard thesis: two or more states in a multiplet of the gauge group of a quantum field theory are ontologically unified if they transform into each under the action of a spacetime transformation. The Redhead-Weingard thesis seems to generate the intuitively correct verdict in a number of cases, including the two SU(2) cases presented above. In ordinary relativistic QFTs, it works because the question of what structure counts as spatiotemporal is settled pretheoretically. But this fact conceals a contingent fact that is tacitly assumed across much theorising about spacetime: that spacetime plays the same inferential role regardless of the theoretical framework within which it is employed. The primary goal of this talk is to demonstrate this contingency by discussing how these roles come apart in supersymmetric quantum field theories.