Philosophy of Physics Seminar (Thursday - Week 4, HT26)

Abstract: In the recent literature on the semantic conception, it has been argued that a bare collection of models subject to kinematical or dynamical conditions is not sufficient to define a theory: additional structure on the space of models is required. In this talk, I will develop a geometric view of theories, according to which a physical theory is a structured space of models equipped with topological and geometric structure, typically organised by a moduli space. Building on this, I propose a more specific framework, the model bundle, in which putative ‘theories’ are models (fibres) of a higher‑level structure. The fibres contain states and quantities, the base is a moduli space, and a structure group of quasi-dualities acts on the fibres; the total space thereby carries natural geometric structure. I will illustrate this with S-duality in the Seiberg–Witten theory, where the moduli space is the complex plane with three punctures and the modular group acts as the structure group. Quasi‑dualities are local transition functions between fibres; when the bundle is trivial, dualities are recovered as global transition functions. I will also discuss how the geometric view bears on discussions of T-duality.

Registration: If you do not hold a university card, please contact the seminar convenor or admin@philosophy.ox.ac.uk at least two working days before a seminar to register your attendance.