Fall semester 2026
October 5, 2026: Dominic Ryder (University of Geneva)
Title: “Is the Standard Model an Effective Field Theory?”
Abstract: Empirically successful quantum field theories are understood by contemporary physicists to be effective field theories. This includes, but is not limited to, the standard model of particle physics. Two important questions arise: what does it mean to be an effective theory, and why should one believe that the standard model is effective? This talk provides answers to these questions.
I distinguish different senses of effectiveness which are often elided. One important sense is the interpretation of a regularized theory as only applicable in a domain specified by a regulator. Another important sense is the failure of a theory on some domain. I clarify the different types of theoretical objects implicit in these senses of effectiveness, and the different kinds of breakdown that can occur in the latter. With these distinctions in hand, we can ask: why think the standard model is effective in the latter, breakdown, sense?
The interpretative sense does not imply the breakdown sense. Therefore, independent argumentation for the breakdown of an effectively interpreted theory, such as the standard model, is required. I provide five better reasons to think the standard model is breakdown-effective: UV-incompleteness, gravity, decoupling theorems, theoretical problems and naturalness, and empirical anomalies. However, none of the resolutions to these problems require abandoning the effective interpretation of theories, in the former sense.
November 2, 2026: India Bhalla-Ladd (University of California, Irvine)
Title: “Cluster Decomposition and Entanglement in Perturbative Algebraic QFT”
Abstract: The Cluster Decomposition Principle requires that distant scattering processes be statistically independent. It is widely regarded as a foundational desideratum for any relativistic quantum theory. However, Dougherty et al. (2024) have shown that standard formalizations of the CDP are incompatible with the spacelike correlations of entangled states. I propose instead to identify the CDP with the Causal Factorization Axiom of perturbative algebraic QFT. This axiom naturally separates the statistical-independence of compactly-supported observables from the basis-dependence of scattered states. I show that observables fulfilling Causal Factorization descend to a Fock Space S-matrix that factorizes iff scattered states are given by non-entangled states on the product algebra. Finally, I discuss the relationship between Causal Factorization and the alternative formalization proposed by Dougherty et al.(2024), drawn from a theorem of Weinberg (1995).
December 7, 2026: Dominik Erhenfels (LMU Munich)
Title: TBA
Abstract: TBA
