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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 5: Quantum Theory 4

AGPhil 5.1: Talk

Wednesday, September 1, 2021, 16:30–17:00, H8

Mereological Atomism's Quantum Problems — •Ryan Miller — University of Geneva, Switzerland

The popular metaphysical view that concrete objects are grounded in their ultimate parts is often motivated by appeals to realist interpretations of contemporary physics (Feynman et al., 2015; Fine, 1992; Pettit, 1993; Loewer, 2009). Given that appeals to small-scale physics are fundamentally quantum mechanical, this paper argues first that mereological atomism is only plausible in conjunction with Bohmianism, and second that it exacerbates Bohmianism's existing tensions with serious Lorentz invariance. Neither of Bohmianism's leading realist competitors yields a decomposition of the physical world into a multiplicity of non-overlapping fundamental concrete objects. Everettians can't rely on decoherence for such a decomposition (Wallace, 2012; Crull, 2013; pace Ney, 2021) and none of the proposed ontological elements for GRW (mass density, flashes, flash families) can play the role of multiple synchronic atomic parts.

Bohmian particles, on the other hand, provide a natural set of ultimate parts for atomists. The trouble is that different reference frames have different particle numbers (Unruh & Wald, 1984), and in classical mereology concrete objects are invariant fusions of determinate parts, so the Bohmian hidden privileged reference frame corresponds to a set of hidden privileged macroscopic concrete objects. Mereological atomism is thus undercut rather than supported by contemporary physics.