Marian J. R. Gilton

Haag’s theorem cries out for explanation and critical assessment: It sounds the alarm that something is (perhaps) not right in one of the standard ways of constructing interacting fields to be used in generating predictions for scattering experiments. Viewpoints as to the precise nature of the problem, the appropriate solution, and subsequently-called-for developments in areas of physics, mathematics, and philosophy differ widely. In this paper, we develop and deploy a conceptual framework for critically assessing these disparate responses to Haag’s theorem. Doing so reveals the driving force of more general questions as to the nature and purpose of foundational work in physics.

This article demonstrates the benefit of studying a classical version of chromodynamics in order to better understand color charge in quantum chromodynamics. Standard presentations of the conservation and confinement of color charge serve to obscure the Lie-algebra-valued character of the conserved Noether charge. This article shows how we can remove these obscuring factors by studying color charge from the vantage point of classical chromodynamics. This key example of color charge illustrates the larger methodological benefit of this classical vantage point: interpreting classical gauge theories helps to delineate the uniquely quantum features of quantum field theories.

David Wallace has recently argued that the eigenstate–eigenvalue (E–E) link has no place in serious discussions of quantum mechanics on the grounds that, as he claims, the E–E link is an invention of philosophers rather than the community of practicing physicists. This raises an historical question regarding the origin of the link. This paper aims to answer this question by tracing the historical development of the link through six key textbooks of quantum mechanics. In light of the historical evidence from these textbooks, it is argued that Wallace provides insufficient grounds for dismissing the E–E link from discussions of quantum mechanics.