Asymmetry, Reduction, and Quantum Field Theory - A Philosophical Investigation – ARQ

Quantum theory emerged over the past century as one of humanity’s most profound scientific achievements. Since its inception, it has generated extensive philosophical inquiry, as its conceptual structure challenges traditional views on the nature of scientific theories, the structure of scientific explanation, and the role of the observer. As the central achievement of the quantum revolution, quantum field theory (QFT) provides the theoretical foundation for the most empirically successful theories in contemporary particle physics while also driving key developments in condensed matter and statistical physics. Despite its extraordinary empirical success, QFT encapsulates the core conceptual challenges of quantum theory for philosophy. Because QFT calculations are notoriously complex, physicists employ various strategies, such as focusing on effective field theories (EFTs) or renormalisation techniques, to manage this complexity.

This project centres on two main questions: (RQ1) What are the metaphysical implications of EFTs for inter-theoretic relationships, the nature of physical laws, and the possibility of emergent phenomena in physics? (RQ2) How should we interpret the epistemological status of indispensable mathematical idealisations, such as infinities and renormalisation, in QFT?

The central objective of this project in the philosophy of science is to investigate the hierarchy of levels of explanation within fundamental physics. This requires examining how QFT achieves its predictive accuracy and analysing its conceptual foundations. The core research hypothesis is that the a-theorem provides a powerful new perspective on these questions. The a-theorem is a recent result in physics that, by focusing on renormalisation group (RG) flows, tracks how a physical theory evolves across energy scales. This hypothesis is pursued because the a-theorem has the potential to revolutionise our understanding of scale and emergence in QFT. The theorem reveals an irreversible loss of degrees of freedom along RG flows, suggesting a hierarchical, asymmetric structure in which, for instance, higher-energy descriptions contain more information than lower-energy ones.

This project will be the first to explore the philosophical significance of these results, specifically how the a-theorem provides a rigorous framework for addressing foundational questions in the philosophy of physics and science. I will argue that the emerging picture strongly supports the idea that EFTs possess a genuine degree of explanatory independence, challenging traditional reductionist views. Additionally, I will argue that the a-theorem offers a concrete framework for understanding renormalisation, providing decisive elements for an anti-reductionist picture according to which physical laws may be scale-dependent.

In the long term, this project aims to develop a framework for addressing longstanding debates in the philosophy of physics and science. In particular, it will connect QFT’s treatment of emergence, renormalisation, and scale hierarchy to discussions on realism, the status of scientific theories, and the role of mathematical structures in explanation. Through its emphasis on emergence, asymmetry, and hierarchical organisation, this project will contribute to a unifying framework with three key elements: (1) an asymptotic view of scientific realism, where explanations converge hierarchically toward truth; (2) a critique of mechanistic explanations in fundamental physics, defending the essential role of structural constraints; and (3) a pluralistic view of scientific explanation, where different levels retain autonomy while being structurally constrained. This project will deepen our understanding of QFT while offering a novel perspective on scientific knowledge.