A New Philosophy of Symmetry: Gauge, Composition, and Empirical Content

One of the most remarkable and pervasive features of our fundamental physical theories is that they possess a symmetry known as 'gauge symmetry', which relates physically identical descriptions of a system. Our project seeks to launch a comprehensive philosophical analysis of gauge symmetry, addressing the following two Big Questions: (1) What is the *empirical significance* of gauge symmetry, and (2) How can empirical content be related to redundancy of description? The project is urgently needed because gauge symmetries seem to defy the standard philosophical story (harkening back to Galileo) of how symmetries encode the *empirical content* of a physical theory; and it is timely because physicists (e.g. Donnelly and Freidel) have recently developed new tools to address this question in a systematic and foundational way. This project aims to answer its Big Questions by developing a comprehensive framework for the study of gauge symmetries, drawing upon recent groundbreaking work in both the physics and philosophy literature. To achieve these tasks, Notre Dame and Oxford will set up a research cluster based around two PIs, visiting researchers, and a postdoctoral fellow. Our deliverables will be four research articles submitted to top physics and philosophy journals, a monograph proposal, and an international conference. The project will impact deeply both the philosophy of science/physics community and the theoretical physics community: As Lee Smolin recently put it, physicists need the help of philosophers to understand the significance of the most foundational concepts that they use on a daily basis. Foremost among these concepts is ‘gauge symmetry’; thus, our results have the potential to usher in an era of extremely fruitful collaboration between science and philosophy.