Symmetries and Representation

Abstract

It is often said in physics that if two models of a theory are related by a symmetry, then the two models provide (or could provide) two different representations of the very same situation, alike the case of two maps of different color for the very same city. It is also said that the situations represented by two models of a theory are indiscernible in some ways when the models in question are related by a symmetry of the theory, just like the situation in the interior of the cabin of a train when the train is at rest in the station is empirically indiscernible from the situation in the interior when the train is moving uniformly (in classical mechanics, these two situations are represented by two models related by a boost). In recent years, philosophers of physics have focused a lot of attention in developing various principles that aim to elucidate these and similar remarks on symmetries, models, physical equivalence, and representation that are widespread in physics practice. The goal of the current article is to provide a critical review of these principles, and suggest a new framework for thinking about these kinds of questions. One important upshot of the paper is that questions of indiscernibility, and questions of the representational capacity of models, must be distinguished from one another.

Symmetries and Measurements

“…In the last two decades or so, the philosophical literature on symmetries has grown rather rapidly. Among other topics, philosophers have explored the connection between symmetries and representation (see Hall and Murgueitio Ramírez [2024] for a recent overview), symmetries and the formulation (and interpretation) of physical theories (e.g., see Møller-Nielsen [2017], Read and Møller-Nielsen [2020] and Luc [2023a]), and, as we will explore in this paper, symmetries and measurement. Why is this last topic of philosophical interest?…”