Physicists often appeal to the beauty of a theory as a way to judge its credibility, and the most prevalent component of this beauty is symmetry. This paper describes the role and structure of symmetry arguments in physics. It demonstrates that the epistemic authority of an appeal to symmetry is based on empirical evidence and is independent of any aesthetic judgment. Furthermore, symmetry in nature is not evidence of design. Just the opposite, symmetry indicates a lack of planning. It is (...) about nature's disregard for details. (shrink)

Of all the concepts of modern physics, there are few that have the sort of powerful, sometimes mysterious, and often awe-inspiring rhetoric surrounding them as has the concept of local gauge symmetry. The common understanding today is that all fundamental interactions in nature are described by so-called gauge field theories. These theories, far from being just any sort of physical theory, are taken to result from the strict dictates of principles of local symmetry---gauge symmetry principles. The experimental and theoretical success (...) of theories based on local symmetry principles has given rise to the received view of these principles as deeply fundamental, as literally "dictating" or "necessitating" the very shape of fundamental physics. The current work aims to make some headway toward elucidating this view by considering the general issue of the physical content of gauge symmetry principles in both their historical and modern theoretical contexts. ;There are two parts to the dissertation: a historical part and a more "philosophical" part. In the first, historical, part I provide a brief genealogy of gauge theories, looking at a number of the seminal works in the birth and development of gauge field theories. My chief claim here is about what one does not find. In contrast to how the modern rhetoric sometimes portrays the matter, the history of gauge field theories does not evidence loaded arguments from a priori gauge symmetry principles or even the "need" for ascriptions of deep physical significance to these principles. The history evidences that the ascendancy of gauge field theories and the characteristic appeal to gauge symmetry principles rests squarely on the heuristic value of these principles. ;In the philosophical component of the dissertation, I turn to an analysis of the gauge argument, the canonical means of understanding the physical content of gauge symmetry principles. I warn against a literal construal of this argument. As I discuss, the argument must be afforded a fairly heuristic and historically based reading. Claims to the effect that the argument reflects the "logic of nature" must, for numerous reasons that I discuss, be taken with a grain of salt. (shrink)

Quantum field theory (QFT) combines quantum mechanics with Einstein's special theory of relativity and underlies elementary particle physics. This book presents a philosophical analysis of QFT. It is the first treatise in which the philosophies of space-time, quantum phenomena, and particle interactions are encompassed in a unified framework. Describing the physics in nontechnical terms, and schematically illustrating complex ideas, the book also serves as an introduction to fundamental physical theories. The philosophical interpretation both upholds the reality of the quantum world (...) and acknowledges the irreducible cognitive elements in its representation. The interpretation is based on an analysis of our ways of thinking as the are embedded in the logical structure of QFT. The author argues that philosophical categories are significant only if they play active and essential roles in our knowledge and hence constitute part of the theories in actual use. Thus she regards physical theories as primary, extracts their categorical structure, and uses it to rethink key philosophical questions. Among the questions this book tries to answer are: What are the quantum properties independent of measurements? How do we refer to individual things in a continuous field? How do theories relate to objects? What are the general conditions of the world and of our ways of thinking that make possible our knowledge of the microscopic realm, which is so intangible and counterintuitive? As a penetrating analysis of vital themes in contemporary science, the book will engage the interest of students and professionals in physics and philosophy alike. (shrink)

The purpose of the paper is to explore different aspects of the covariance of non-relativistic quantum mechanics. First, doubts are expressed concerning the claim that gauge fields can be 'generated' by way of imposition of gauge covariance of the single-particle wave equation. Then a brief review is given of Galilean covariance in the general case of external fields, and the connection between Galilean boosts and gauge transformations. Under time-dependent translations the geometric phase associated with Schrödinger evolution is non-invariant, and the (...) significance of this result is briefly analysed. The covariance properties of Schrödinger dynamics are then brought to bear on certain versions of the modal interpretation of quantum mechanics. The conclusion that it is only relational properties that can be considered coordinate- or gauge-independent elements of reality is reinforced by appeal to the theory of quantum reference frames due to Aharonov and Kauffher. , Cambridge University Press ; pp. 45-70.). (shrink)

Einstein proclaimed that we could discover true laws of nature by seeking those with the simplest mathematical formulation. He came to this viewpoint later in his life. In his early years and work he was quite hostile to this idea. Einstein did not develop his later Platonism from a priori reasoning or aesthetic considerations. He learned the canon of mathematical simplicity from his own experiences in the discovery of new theories, most importantly, his discovery of general relativity. Through his neglect (...) of the canon, he realised that he delayed the completion of general relativity by three years and nearly lost priority in discovery of its gravitational field equations. (shrink)