Philosophy & History of Physics

  • [Preprint]

    With Eleanor March and James Owen Weatherall

    We discuss and then resolve a tension between how physicists treat gauge bosons and the celebrated “Wu-Yang dictionary”, which identifies particle physics terminology with that of principal bundles and principal connections. We show how this tension leads to an interpretative choice that is not widely discussed in the physics literature. We then show how the same considerations present a dilemma for a recent “particle-first” approach to YangMills theory due to Henrique Gomes. Either the particle-first approach has surplus structure as compared to principal-bundle-based approaches, or gauge bosons are not sections of vector bundles.

  • [Preprint]

    Forthcoming in Studies in the History & Philosophy of Science

    I present an analysis of the changes to intra-scientific communication in postwar American physics. In particular, I focus on a case study of the technical typists who worked for the American Institute of Physics (AIP) journals, especially the Physical Review (PR), c. 1962-1977. I argue PR became a trading zone amidst the page-charge crisis, and analyze the networks of physicists, typists, editors, and copy-editors that emerged to resolve this threat to community-level objectivity. Challenging the picture of typist as “automaton,” I identify the skills and technical knowledge needed to perform manuscript transcription, and offer an account of the material culture of intra-scientific communication to situate the typists’ epistemic role in the broader context of “Big Science” changes to postwar physics. I claim this is a case of an epistemic contribution that has been instrumentalized, akin to human computers and human scanners. However, unlike other cases of instrumentalization, technical typists were not directly involved in the production or critique of scientific data. Rather, their novel contributions occurred in the new field of mathematical typesetting that emerged from this trading zone. Thus, I seek to differentiate the material culture of scientific experiments from the material culture of intra-scientific communication. I see this project as an extension of Galison’s trading zone framework, recognizing that there are many more material objects besides those of the laboratory that are created in the scientific process.

  • Forthcoming as an APS Back Page article [preprint]

    Winner of the 2025 APS Forum on History and Philosophy Essay Contest

    In the 20th and 21st centuries, the practice of American physics has grown far beyond small experiments confined to home laboratories. We find ourselves operating within a much larger industry of science, which necessitates the cooperation of many people from vastly different walks of life, with areas of expertise stretching administration, politics, engineering, and the academy. This rapid change in landscape accelerated after World War II, and there are many aspects of this transformation not yet documented or understood. One of these changes regards the publishing operations of the major physics journals -- an institution on whose health scientific discourse and intellectual critique relies. In this essay, I will introduce a group of women employed by The Physical Review whose work in technical typesetting single-handedly resolved a significant threat to the major American physics journals c. 1950-1970. They are the ``technical typists.''

HEP and Astronomy

  • With Izzy Ginnett and Tim Tait

    Physical Review D (doi.org/10.1103/nmpt-fwz6)

    We explore leptogenesis during a cosmological epoch during which the electroweak SU(2)L force is confined. During weak confinement, there is only one conserved non-anomalous global charge, r, which is a linear combination of lepton-number, baryon-number, and hypercharge. The inclusion of heavy Majorana neutrinos leads to an r-charge and CP-violating interaction, allowing for the generation of an r-charge asymmetry, which translates into a baryon asymmetry post SU(2)L deconfinement. Determining the resulting baryon asymmetry as a function of the model parameters, we find that the predicted baryon-asymmetry can match observations for a wide swath of parameter space. While leptogenesis under the assumption of a standard cosmology relies on the complex phase of the neutrino Yukawa couplings, the asymmetry generated in this novel background cosmology primarily depends on a strong phase from SU(2)L confinement and favors negligible CP-violation in the right-handed neutrino decays.

  • With Jorge Martínez-Palomera, Paulina Lira, Francisco Förster, and Richard M. Plotkin

    The Astrophysical Journal (doi.org/10.3847/1538-4357/ab5f5b)

    Intermediate-mass black holes (IMBHs) have masses between 10^2 and 10^6 M⊙ and are key to our understanding of the formation of massive black holes. The known population of IMBHs remains small, with a few hundred candidates and only a handful of them confirmed as bona fide IMBHs. Until now, the most widely used selection method is based on spectral analysis. Here we present a methodology to select IMBH candidates via optical variability analysis of the nuclear region of local galaxies (z <= 0.35). Active IMBHs accreting at low rates show small amplitude variability with timescales of hours, as is seen in one of the known IMBHs, NGC 4395. We found a sample of ∼500 galaxies demonstrating fast and small amplitude variation in their week-based light curves. We estimate an average occupancy fraction of 4% and a surface density of ∼3 deg^{−2}, which represent an increase by a factor of ∼40 compared to previous searches. A large fraction (78%) of the candidates are in spiral galaxies. We preliminarily confirm the active galactic nucleus nature of 22 sources via Baldwin, Phillips, and Terlevich diagrams using Sloan Digital Sky Survey legacy spectra. Further confirmation of these candidates will require multiwavelength observations, especially in X-ray and radio bands.

Working Papers

  • The Cluster Decomposition Principle requires that distant scattering processes be statistically independent. It is widely regarded as a foundational axiom for any relativistic quantum theory. However, Williams et al. (2024) have shown that standard formalizations of the CDP are incompatible with the spacelike correlations of entangled states. Consequently, I propose to identify the CDP with the Causal Factorization Axiom in perturbative algebraic QFT. This axiom naturally separates the statistical-independence of observables from state-dependent Fock space representations. I show that observables fulfilling Causal Factorization descend to an S-matrix that factorizes iff asymptotic states are given by non-entangled states on the product algebra.

  • I present a defense of the idea that some matter fields are faithfully represented as sections of associated vector bundles, and some matter fields are faithfully represented as connections on a principal bundle, in the context of classical Yang-Mills theory. This analysis clarifies a conceptual question from Weatherall’s Frame Interpretation (Weatherall (2016), March and Weatherall (2025)), in which the conceptual significance of the principal bundle is tied to its associated vector bundles, in analogy with relationship between the frame bundle and the tangent bundle in General Relativity. Under the Frame Interpretation, we interpret sections of principal bundles as frame fields for associated vector bundles; how, then, should we interpret the free Yang-Mills theory? Under the received view, it is the associated gaugenatural vector bundles that represent matter, while the principal bundle plays a crucial coordinating role, but nonetheless does not represent matter or possible states of matter. I argue that nothing in the formalism prevents us from interpreting connections on a principal bundle as a type of physical matter field, and that the Generalized Utiyama Theorem offers a positive sense in which we should treat the connection as a physical field – namely that it acts uniquely as a non-trivial dynamical variable as a consequence of gauge-covariance. Ultimately, this is completely consistent with the Frame Interpretation: sections of principal bundles do not represent matter fields, but connections on them do.

    I argue that this perspective helps clarify and defuse criticisms of the Frame Interpretation put forth by Jacobs (2023) and Gomes (2024a). In particular, I argue that both critics can be seen as motivated by a discomfort with interpreting the principal bundle in the absence of associated vector bundles. As a result, they seek out different mathematical structures both in emphasis and in kind than already present in the principal bundle formalism. I believe that this is a misguided strategy, and that the real issue comes from an impoverished “physical field” concept rather than any issue in the geometrical formalism.

    I take the opposite strategy, and mine the existing formalism for positive reasons to consider expanding the “physical field” concept to connections on a principal bundle as well as associated vector bundles. Both admit gauge-natural descriptions, and enter non-trivially (and in some sense uniquely) into the gauge-natural Lagrangians that govern physical systems of interest. The generalized Utiyama Theorem (Kol´aˇr et al. (1993), Eck (1980)) and the machinery of gauge-natural Lagrangians helps make precise the sense in which the unique and non-trivial Yang-Mills field dynamics follows from gauge-covariance, a foundational commitment to what constituted a “physical field” that was implicit in the development of gauge theory and minimal coupling in 1970s theoretical particle physics.

  • (work in progress, abstract forthcoming)