Sébastien Rivat

The idea of using lattice methods to provide a mathematically well-defined formulation of realistic effective quantum field theories (QFTs) and clarify their physical content has gained traction in the last decades. In this paper, I argue that this strategy faces a two-sided obstacle: realistic lattice QFTs are (i) too different from their effective continuum counterparts even at low energies to serve as their foundational proxies and (ii) far from reproducing all of their empirical and explanatory successes to replace them altogether. I briefly conclude with some lessons for the foundations of QFT.

Scientific realists with traditional semantic inclinations are often pressed to explain away the distinguished series of referential failures that seem to plague our best past science. As recent debates make it particularly vivid, a central challenge is to find a reliable and principled way to assess referential success at the time a theory is still a live concern. In this paper, I argue that this is best done in the case of physics by examining whether the putative referent of a term is specifiable within the limited domain delineated by the range of parameters over which the theory at stake is empirically accurate. I first implement this selective principle into a general account of reference, building on Stathis Psillos’s works. Then, I show that this account offers a remarkably reliable basis to assess referential success before theory change in the case of effective theories. Finally, I briefly show that this account still works well with other physical examples and explain how it helps us to handle problematic cases in the history of physical sciences.

Renormalisation Group (RG) methods are one of the theoretical masterpieces of postwar physics whose historical development still remains largely unexplored. This article traces the origins of Kenneth Wilson's RG from 1956 to 1965, with a particular focus on its relationship to Murray Gell-Mann and Francis Low's RG published in 1954. I argue that there is ultimately little methodological and conceptual continuity between their respective versions. The article briefly concludes with the evolution of the Wilsonian RG from 1965 to the early 1970s.

This article has two aims. First, I undertake an extensive review of the Higgs mechanism and its connections with spontaneous symmetry breaking and the Goldstone theorem. I take the opportunity to expound and discuss a certain number of philosophical issues, amongst them surplus structure and redundancies. Second, I offer a defence of the metaphor according to which ‘gauge fields eat Goldstone bosons to gain a mass’ as sensible rather than merely misleading. It is sensible because there is a direct physical correspondence between the longitudinal polarization of massive gauge fields and Goldstone bosons, which is not merely set by a gauge-fixing procedure. In these terms, I wish to argue that the mechanism which allows for the discovery of the Higgs boson has more than merely heuristic and methodological virtue.

This survey covers some of the main philosophical debates raised by the framework of effective field theories during the last decades. It is centered on three issues: whether effective field theories underpin a specific realist picture of the world, whether they support an anti-reductionist picture of physics, and whether they provide reasons to give up the ultimate aspiration of formulating a final and complete physical theory. Reviewing the past and current literature, we argue that effective field theories do not give convincing reasons to adopt a particular stance towards these speculative issues. They hold good prospects for asking ontologically perspicuous and sensible questions about currently accessible domains. With respect to more fundamental questions, however, the only certainty is provisional and instrumental: effective theories are currently indispensable for conducting fruitful scientific research.

The view that our best current physics deals with effective systems has gained philosophical traction in the last two decades. A similar view about open systems has also been picking up steam in recent years. Yet little has been said about how the concepts of effective and open systems relate to each other despite their apparent kinship—both indeed seem at first sight to presuppose that the system in question is somehow incomplete. In this paper, I distinguish between two concepts of effectiveness and openness in quantum field theory, which provides a remarkably well-developed theoretical framework to make a first stab at the matter, and argue that on both counts, every realistic effective system in this context is also open. I conclude by highlighting how the discussion opens novel avenues for thinking of systems as open across scales.

Philosophers of physics have spent much effort unpacking the structure of gauge theories. But surprisingly, little attention has been devoted to the question of why we should require our best theories to be locally gauge invariant in the first place. Drawing on Steven Weinberg's works in the mid-1960s, I argue that the principle of local gauge invariance follows from Lorentz invariance and other natural assumptions in the context of perturbative relativistic quantum field theory. On this view, gauge freedom is a mere accidental feature of an already highly constrained set of quantities; the distinctive structure of our best gauge theories, in turn, traces back to the peculiar space-time transformation properties of particles like photons, gluons, and gravitons. I conclude by drawing a few interpretative lessons for the philosophy of gauge theories.

This article traces the origins of Kenneth Wilson's conception of effective field theories (EFTs) in the 1960s. I argue that what really made the difference in Wilson's path to his first prototype of EFT are his long-standing pragmatic aspirations and methodological commitments. Wilson's primary interest was to work on mathematically interesting physical problems and he thought that progress could be made by treating them as if they could be analyzed in principle by a sufficiently powerful computer. The first point explains why he had no qualms about twisting the structure of field theories; the second why he divided the state-space of a toy model field theory into continuous slices by following a standard divide-and-conquer algorithmic strategy instead of working directly with a fully discretized and finite theory. I also show how Wilson's prototype bears the mark of these aspirations and commitments and clear up a few striking ironies along the way.

Williams and J. Fraser have recently argued that effective field theory methods enable scientific realists to make more reliable ontological commitments in quantum field theory than those commonly made. In this paper, I show that the interpretative relevance of these methods extends beyond the specific context of QFT by identifying common structural features shared by effective theories across physics. In particular, I argue that effective theories are best characterized by the fact that they contain intrinsic empirical limitations, and I extract from their structure one central interpretative constraint for making more reliable ontological commitments in different subfields of physics. While this is in principle good news, this constraint still raises a challenge for scientific realists in some contexts, and I bring the point home by focusing on Williams’s and J. Fraser’s defense of selective realism in QFT.

In this paper, I propose a general framework for understanding renormalization by drawing on the distinction between effective and continuum Quantum Field Theories (QFTs), and offer a comprehensive account of perturbative renormalization on this basis. My central claim is that the effective approach to renormalization provides a more physically perspicuous, conceptually coherent and widely applicable framework to construct perturbative QFTs than the continuum approach. I also show how a careful comparison between the two approaches: (i) helps to dispel the mystery surrounding the success of the renormalization procedure; (ii) clarifies the various notions of renormalizability; and (iii) gives reasons to temper Butterfield and Bouatta's claim that some continuum QFTs are ripe for metaphysical inquiry (Butterfield & Bouatta, 2014).