Prof. Dr. Elena Castellani

Research project - Objects, Structures and Symmetries: The case of elementary particles

With the flourishing of structural realism, both in its epistemic and ontic form, the role of structure has become a central topic in current debates on scientific theories, scientific objects and scientific representation. Structural approaches are not novel in the philosophy of science. Notably, the fundamental role acquired in contemporary physics by symmetry principles and their exploitation through group theory techniques has motivated a group-theoretic approach to the question of characterising objectivity and physical objects, mainly inspired by the work and reflections of Hermann Weyl and Eugene Wigner. In particular, the possibility of classifying elementary particles by means of the irreducible representations of the theory's symmetry group, after the seminal 1939 paper by Wigner

on the unitary representations of the Poincaré group, has been taken as a basis for a reconceptualization of physical objects in structuralist terms. A further step taken by the most common version of ontic structural realism (e.g. French, 2014) – i.e. the position maintaining that “all that there is, is structure” – has been to identify as real the very structures on the grounds of which physical objects are characterised. Using as a case study the notion of elementary particle and its relation to symmetry, I will discuss the legitimacy of this step. I will analyse, both from a philosophical and a historical perspective, what the actual use of symmetry groups and related structural tools at the level of scientific practice do indeed imply when addressing the issue of physical objects and, more generally, scientific representation.