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Dr. Karim Baraghith & Nina Nicolin (Univ. Düsseldorf): Spatial Separation of Magnetic Moment and Location

Aus den Instituten Forschungsseminar Theoretische Philosophie Forschungsseminar


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 ap-pear in QFT anymore. This is what separates QFT from e.g. classical mechanics or quantum me-chanics. 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 spe-cific combination of the properties which constitute the thing in the first place.
In this paper, we are going to argue for this very interpretation of QFT. We 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 neu-trons 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 neu-trons 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 particle’s properties and not the particle itself as fundamental – is probably the most compati-ble ontological interpretation of this phenomenon. 


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

Author‘s Information

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 lies on logic, philosophy of science and the intersection of philoso-phy and physics. 

Karim Baraghith studied Philosophy, History and Biology. He is associated member of the DFG research group ‘Inductive Metaphysics’, led by Prof. Gerhard Schurz and applied member of the DFG research group ‘Explanatory Scope of Generalized Darwinism’, led by Thomas Reydon. His main research interest lies in generalized - and cultural evolution, philosophy of biology and philosophy of science. 


14.12.2021, 18:30 Uhr - 20:00 Uhr