Understanding Gauge
I consider two usages of the expression “gauge theory.” On one, a gauge theory is a theory with excess structure; on the other, a gauge theory is any theory appropriately related to classical electromagnetism. I make precise one sense in which one formulation of electromagnetism, the paradigmatic gauge theory on both usages, may be understood to have excess structure and then argue that gauge theories on the second usage, including Yang-Mills theory and general relativity, do not generally have excess structure in this sense.
Sophistication about Symmetries
Suppose that one thinks that certain symmetries of a theory reveal ‘surplus structure’. What would a formalism without that surplus structure look like? The conventional answer is that it would be a reduced theory: a theory that traffics only in structures invariant under the relevant symmetry. In this article, I argue that there is a neglected alternative: one can work with a sophisticated version of the theory, in which the symmetries act as isomorphisms. 1. Introduction2. Symmetry3. Reduction4. Sophistication5. Equivalence6. Conclusion Appendix Introduction Symmetry Reduction Sophistication Equivalence Conclusion Appendix
Symmetry, Structure, and Spacetime
In this book Rickles considers several interpretative difficulties raised by gauge-type symmetries (those that correspond to no change in physical state). The ubiquity of such symmetries in modern physics renders them an urgent topic in philosophy of physics. Rickles focuses on spacetime physics, and in particular classical and quantum general relativity. Here the problems posed are at their most pathological, involving the apparent disappearance of spacetime! Rickles argues that both traditional ontological positions should be replaced by a structuralist account according to which relational structure is what the physics is about. Unified treatment of gauge symmetries and their relationship to ontology in physics Brings philosophy of space and time into step with developments in modern physics Argues against the received view on the implications of symmetries in physics Provides elementary treatments of technical issues Illustrates a novel defense of structuralism