Rationale
The development of theoretical physics after 1945 has been marked by an increased attempt to both study physical systems "scale by scale" in some independent fashion and build models that could potentially work across all scales. This workshop aims to engage with conceptual aspects of this transformation. In particular, we will give a close look at the set of methods, models, theories, mechanisms and principles that physicists have devised to articulate hierarchies of scales and unify them (e.g., renormalization and renormalization group methods, effective field theories, thermal field theories, grand unified theories, symmetry breaking mechanisms, new unifying symmetries, new approximation methods).
Program and registration
April 9
8:30 – 9:00: Coffee & tea
8:50 – 9:00: Welcoming remarks
9:00 – 10:15: Alexander Blum: “Beyond Power Counting: On the Historical Connection Between Renormalizability and Gauge Symmetry”
10:15 – 10:30: Break
10:30 – 11:45: Victoria Zwierzyk-Teles: “The Symmetries That Were Broken”
11:45 – 13:00: Rocco Gaudenzi: “Spontaneous Symmetry Breaking Across Scales: From Physics to Life and Brain”
13:00 – 14:15: Lunch
14:15 – 15:30: Adam Koberinski: “Particle Physics Across Temperature Scales”
15:30 – 16:45: Sébastien Rivat: “The Evolution of Steven Weinberg’s Conception of Effective Field Theories in the 1970s”
16:45 – 17:00: Break
17:00 – 18:15: Robert van Leeuwen: “The “Problem of Gauge Hierarchies” in Early Unification Physics”
April 10
8:30 – 9:00: Coffee & tea
9:00 – 10:15: John Dougherty: “The Background of Batalin–Vilkovisky Quantization”
10:15 – 10:30: Break
10:30 – 11:45: Francisco Caldéron: ““Profound Results from Not-very-profound Properties”: The Renormalization-group Route to Asymptotic Freedom”
11:45 – 13:00: Vincenzo Nespeca: “A Brief History of Asymptotic Safety”
13:00 – 14:15: Lunch
14:15 – 15:30: Emilia Margoni: “Cluster Transfer: The Renormalization Group Case”
15:30– 16:45: James Fraser: “The Many Faces of the Renormalization Group”
Registration:
Please register by sending an email to sebastien.rivat@lmu.de before April 7, 2026.
Venue
CEPP/ZEPP library, Room M 210, Geschwister-Scholl-Platz 1, 80939 Munich
Organizers
- Alexander Blum
- Sebastien Rivat
The event is generously supported by the Volkswagen Foundation.
Abstracts
Alexander Blum: Beyond Power Counting: On the Historical Connection Between Renormalizability and Gauge Symmetry
I will discuss the historical evolution of the concept of (non-)renormalizability, starting with Heisenberg and Pauli's 1930s categorization of quantum field theories into those of first and second type, according to their behavior at ultrahigh energies. I reconstruct the emergence of the modern power-counting criterion around 1950 and then describe the efforts to understand theories that were renormalizable even though they shouldn't be (Stueckelberg field) and then to deliberately construct such theories for the charged vector bosons of the weak interaction. In particular, I reflect on how gauge invariance gradually came to be identified as the relevant criterion to identify and construct renormalizable theories.
Francisco Caldéron: “Profound Results from Not-very-profound Properties”: The Renormalization-group Route to Asymptotic Freedom
This paper traces how Kenneth Wilson and Kurt Symanzik extended the renormalization group techniques developed by Murray Gell-Mann and Francis Low in the early 1950s, reshaping quantum field theory's approach to the nucleus and laying the groundwork for the discovery of asymptotic freedom in the early 1970s. I focus on Wilson's development of the operator product expansion, a central tool in contemporary quantum field theory that has been historiographically underexplored compared to the genealogy of the Wilsonian renormalization group, and on Symanzik's derivation of what is now known as the Callan-Symanzik equation. I also discuss how Wilson's and Symanzik's work fits into the prehistory of asymptotic freedom, which remains underexplored despite its prominent role in quantum field theory's consolidation as the framework for particle physics. Throughout the paper, I emphasize the role of perturbation theory and approximations, as well as Wilson and Symanzik's attempts to circumscribe and transgress perturbation theory's domain of applicability.
John Dougherty: The Background of Batalin–Vilkovisky Quantization (joint work with Alexander Blum)
In 1981, Batalin and Vilkovisky introduced a new procedure for the quantization of field theories. This procedure has gone on to be of practical use and theoretical interest, especially on the basis of later re-interpretations. But the original interpretation of the Batalin–Vilkovisky procedure is obscure. Batalin and Vilkovisky's presentation is axiomatic, and not all of the axioms have explicit or obvious motivation. In particular, their procedure invokes a novel set of fields, which they call "antifields", without clear precedent or use. In this talk, I reconstruct some of the context of Batalin and Vilkovisky's proposal and related work associated with the Lebedev Physical Institute in the 1970s. This context suggests a reading of Batalin and Vilkovisky's axioms and antifields on which they are a natural development in a search for a systematic theory of field quantization that permits a general proof of renormalizability and is applicable to quantum theories of gravity.
James Fraser: The Many Faces of the Renormalization Group
The term “renormalization group” is ambiguous and can be used to refer to different mathematical structures, which can also be subject to different physical interpretations. This paper surveys this landscape of renormalization group concepts and what is known about the relations between them. I conclude by discussing whether the various renormalization groups are in fact conceptually unified and if so what it is that unifies them.
Rocco Gaudenzi: Spontaneous Symmetry Breaking Across Scales: From Physics to Life and Brain
Spontaneous symmetry breaking (SSB) has been one of the most productive conceptual tools of postwar theoretical physics, explaining how differentiated, ordered structure emerges from symmetric laws. This talk examines SSB as a cross-scale principle, asking what it means for the same formal structure to do explanatory work across physics, biology, and cognition. A first question concerns the status of SSB itself: is it a mechanism, a phenomenon, a structural pattern, or an explanatory principle — and does it play the same role at every scale, or does its epistemic character shift as it travels across disciplines? A second, and deeper, question is whether the ubiquity of SSB across scales reveals genuine structural unity in nature, or rather the remarkable portability of a mathematical template that we bring to diverse phenomena. Running through both is the figure of Nambu's cascade of symmetry breakings — a vision of genesis without ad hoc explicit asymmetry, in which differentiated structure at every scale traces back to a chain of prior symmetry breakings.
Adam Koberinski: Particle Physics Across Temperature Scales
Post World War II, physicists working on the Manhattan Project used their newfound knowledge of high-energy nuclear interactions to better understand the processes powering stars. As particle physics developed complete accounts of the electromagnetic, strong, and weak forces, the development of the big bang model of cosmology provided a testing ground for high-energy physics, ultimately culminating in finite-temperature quantum field theory by the late 1970s. In this talk, I trace the conceptual history linking particle physics, cosmology, high energies, and high-temperatures from big bang nucleosynthesis to spontaneous symmetry breaking via phase transitions in the early universe. The main conceptual focus will be on the theoretical tools needed to extend vacuum quantum field theory---which was heavily dependent on the S-matrix formalism---to finite-temperature domains.
Robert van Leeuwen: The “Problem of Gauge Hierarchies” in Early Unification Physics
In the late 1970s and early 1980s, the related assertions of the “gauge hierarchy problem” and “naturalness” emerged as prominent perceived problems in elementary-particle theory. I discuss part of this historical development from the perspective of theorists’ unified theory construction, arguing how the assessment that the newly formulated Standard Model of particle physics was an “effective” theory (in the basic sense of “not fundamental”), the realist aspiration of theorists to explain ‘arbitrary’ parameters, and the employment of the technical resources of unified gauge groups and supersymmetry were all intertwined. I then discuss how the increased significance attributed to problems of gauge hierarchy and naturalness in the early 1980s, and the introduction of supersymmetry as a potential solution, were closely connected, for instance in programmatic accounts by Bruno Zumino and Edward Witten. The attractiveness of this line of reasoning was in part that it bridged theorists’ ongoing attempts at constructing unified supersymmetric theories, prominently extended supergravity, and more experimentally-oriented supersymmetric model-building. To conclude, I indicate how all this was embedded in the more long-term development of unification physics and string theory.
Emilia Margoni: Cluster Transfer: The Renormalization Group Case (joint work with Elena Castellani)
Knowledge transfer, a phenomenon widely analyzed within several research areas, regards the circulation and rearrangement of ideas, models, methodologies, as well as domain-specific practices and protocols within different fields of inquiry. Recently, there has been a renewal of interest in the nature and methodology of such transfer processes, their applicative potential as well as their limitations. Within the context of this endeavor, we address the import of knowledge transfer from the standpoint of theory building and appraisal. Our focus will be the birth and development of the renormalization group as a particularly instructive cross-fertilization process between quantum field theory, statistical mechanics and condensed matter physics. We show that this case study requires enlarging the so-far adopted units of knowledge transfer, thus introducing the notion of cluster transfer. A final mention to possible applications in currently under-development research programs will be provided.
Vincenzo Nespeca: A Brief History of Asymptotic Safety
The quest for a consistent quantum theory of gravity remains one of the preeminent challenges in theoretical physics. The perturbative non-renormalizability of gravitational field theories led many to conclude that gravity could not be described within a standard field-theoretic framework, prompting the development of radically different theories. In contrast, the Asymptotic Safety program — pioneered by Steven Weinberg in the late 1970s — proposes a compelling alternative whose core premise is simple: gravity may be renormalizable at a non-perturbative level if its Renormalization Group (RG) flow is governed by a UV-attractive Non-Gaussian Fixed Point. While the conceptual basis is clear, the technical implementation involves significant complexity. This talk will trace the historical evolution of the idea, examining both its conceptual foundations and technical developments, and will conclude with an overview of the field’s current status.
Sébastien Rivat: The Evolution of Steven Weinberg’s Conception of Effective Field Theories in the 1970s
Effective Field Theories (EFTs) play a central role in contemporary physics, from subatomic particle physics to early universe cosmology. Yet their history remains largely underexplored. This talk traces the evolution of Steven Weinberg's mature conception of EFTs in the 1970s. I first briefly present Weinberg's early concept of effective theory in 1966-1968: namely, a covariant model expansion in some characteristic scale, built up independently of more fundamental models. Then, I discuss the impact of three main theoretical developments on Weinberg's conception of EFTs in the 1970s: (i) the revival of fundamental field theory in 1971-72 with the renormalizability proof of spontaneously broken non-abelian gauge theories; (ii) the development of Grand Unified Theories in 1972-1974; (iii) Weinberg's engagement with Wilsonian renormalization group methods in 1975-1976. I argue that those developments did not fundamentally change Weinberg's distinctive conception of EFTs.
Victoria Zwierzyk-Teles: The Symmetries That Were Broken
The incorporation of symmetry breaking into quantum field theory is often, with retrospection, discussed through the lens of the Higgs mechanism that it eventually led to. Yet, both during its introductory period and within the historical narrative, discussions lack clarity regarding the symmetry the notion was being applied to, despite its well-known result. I therefore find it key, as I begin my PhD, to examine how the phenomenological nature of the symmetries being ‘broken’ evolved throughout its most formative period, which I restrict as from the 1950s up to 1964.
In particular, I aim to emphasise in this talk that Nambu’s incorporation of superconductive symmetry breaking principles around 1960 did not take place in isolation but overlaid an already active discussion about how gauge-invariant field theories might accommodate massive vector bosons. By tracing how the different strands of approach interacted, I explore whether or not this then signified a shift in phenomenological perceptions of symmetry breaking and mass. Within this context, I also draw attention to the rise and fall of Heisenberg as an historically under-emphasised proponent of the ‘world’ ground state.