SOPhiA 2021

Salzburgiense Concilium Omnibus Philosophis Analyticis

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Programme - Talk

Spatial Separation of Magnetic Moment and Location as an Argument for a Trope-Ontological Interpretations of Quantum Field Theory
(Philosophy of Science, )

It has been suggested to interpret particles in quantum field theory (QFT) as bundles of tropes, see e.g. Kuhlmann (2012). Following this interpretation, neither particles nor fields strictly appear in quantum field theory anymore. This is what separates quantum field theory from e.g. classical mechanics or quantum theory. What constitutes the basic ontology of QFT? If we see tropes as the basic units, particles are ``nothing but'' bundles of tropes; they are constituted by particular instead of universal properties. In this reading, a ``thing'' (like a particle) does not ``have'' its properties, it is the specific combination of the properties which constitute the thing in the first place.

In this paper, I am going to argue for this very interpretation of QFT. I will present an empirical matter-wave interferometer experiment (Denkmayr et. Al. _2014_), which shows that one can indeed separate a particle's properties, experimentally. This seemingly paradoxical phenomenon has also been referred to as the ``Chesire Cat''. It indicates that when sending neutrons through a silicon crystal interferometer, while performing weak measurements in order to probe the location of the particle and its magnetic moment, the system behaves as if the neutrons go through one beam path, while their magnetic moment travels along the other.

Taking these observations seriously, it seems to be the case that what we call a ``property'' may exist fundamentally and independently of its particle (or at least can be isolated from it). I am going to argue that a trope theoretical interpretation of quantum particles -- which sees the particles properties and not the particle itself as fundamental -- is probably the most com-patible ontological interpretation of this phenomenon.

-- Denkmayr, T. et. al. (2014): Observation of a quantum Cheshire Cat in a matter-wave interferometer experiment, Nature Communications 5:4492, DOI: 10.1038.
-- Kuhlmann, M. (2012): Interpretation der Quantenfeldtheorie, in: Esfeld, M. (ed.), Philosophie der Physik, Suhrkamp, Berlin.

Chair: Daniela Schuster
Time: 19:30-20:00, 09 September 2021 (Thursday)
Location: SR 1.006
Remark: (Online Talk)

Nina Nicolin 
(Heinrich-Heine-University, Duesseldorf, Germany)

Nina Nicolin studied physics and philosophy at the Heinrich-Heine-University, Duesseldorf. She has a bachelor in physics and is currently finalizing her bachelor in philosophy and her master in physics. Her research focus is currently on logic, philosophy of science and the inter-section of philosophy and physics.

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