The Arbitrariness of the Local Gauge Symmetry

Alexandre Guay (Department of History and Philosophy of Science, University of Pittsburgh)


Abstract
In the context of physics symmetry is defined as an immunity to possible change. Thus a symmetry is always relative to a class of changes and what is invariable under this class must be specified. In most contexts the application of this concept is not philosophically puzzling, but in a few we meet difficulties of interpretation. Local gauge symmetry in Yang-Mills theories is one of these problematic cases. A local gauge symmetry is defined as a certain class of local changes of the fields that do not affect the empirical outcome of a particular theory. If we want to go beyond this fact and specify exactly what should not change in order to conserve the empirical content of a physical theory, we encounter conceptual problems. Since no observable quantity allows us to distinguish between situations related by a gauge transformation, how can we even know if there is an active interpretation of that change? At first sight local gauge symmetry seems to be a redundancy of the theory. On the other hand we often encounter in physics the opinion that gauge arbitrariness is a deep and far-reaching principle. Since 3 of the 4 fundamental interactions are modeled by Yang-Mills theory, this opinion seems grounded. But how can redundancy could be profound? The idea seems absurd, since profundity in the context of physics is associated with capturing the structure of the world through models and theories. A redundancy at best refers to a surplus of structure in the theory but does not refers in anyway to the world. In this talk I will explore this tension and show how local gauge symmetry is a by-product or accompaniment of the specific dynamics of interaction.


Date: Wednesday, November 24, 2004
Time: 4:00 PM
Place: Concordia University, Loyola Campus, Science Pavilion (Building SP), 7141 Sherbrooke Street West, 3rd Floor
Room: SP 365.01
Contact: (514) 848-2424 ext 2595

Note: There are regular shuttle buses traveling between Sir George Williams Campus (1455 de Maisonneuve Blvd. W.) and Loyola Campus; see Shuttle bus schedule.



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