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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 5: Foundations of Quantum Mechanics I

AGPhil 5.2: Talk

Wednesday, March 12, 2025, 14:30–15:00, HS XVII

How can we detect localized particles? — •Alexander Niederklapfer — London School of Economics and Political Science, United Kingdom

The consensus in philosophy of physics is that quantum field theories are, on the fundamental level, not about particles. However, almost all contact of the theories with empirical observations happens in terms of particle experiments. Thus, it is an important task to recover the particle phenomenology from the theory, and one of the main aspects of this is localizability: there are several no-go theorems that show that there cannot be localized states in quantum field theories, and there are as many attempts to reconcile this with the appearance of being able to detect localized particles in experiment.

I compare approaches by Wallace, Halvorson and Clifton, Haag, and Buchholz in terms of their ontological commitments about the non-localizability of physical systems. While some of them employ mathematically similar methods to recover a particle notion, I propose that the differences of the approaches can be attributed to the different stances on the representational relations of the theory not only with the physical systems themselves, but, more importantly, the representation and role of the actual particle measurement devices and methods. This, in turn, shows that some of the reasons to reject a particle ontology for QFTs rest on assumptions about measurement that are still controversially discussed in the literature.

Keywords: Quantum Field Theory; Particles; Ontology; Representation