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10Nov

Sigma Club Seminar by Dr James Fraser (IHPST, Université Paris 1 Panthéon-Sorbonne)

Hosted by the Department of Philosophy, Logic and Scientific Method and CPNSS.
In person at LAK 2.06, Lakatos Building, London, WC2A 2AE United Kingdom. Online (Via Zoom)
Monday 10 November 2025 4pm - 5.30pm

Title: How far can we go with divergent series?

Abstract: Perturbative expansions in quantum field theory (QFT) are divergent series, even after renormalization. Some theorists have concluded from this that perturbation theory is entirely irrelevant to the foundations of QFT, and that new non-perturbative methods are needed to understand the content of the theory. Another tradition, which has emerged in stops and starts since the late 1960s, views the divergence of perturbation theory as an opportunity rather than a dead-end. On this second view, the large-order behaviour of the expansion is a source of information about non-perturbative effects and maybe even the key to understanding the content of empirically successful QFTs. I discuss the back and forth between these pessimistic and optimistic perpsectives of the foundational mileage of perturbation theory.

This event will take place in person on LSE’s campus. However, those unable to attend in person will have the option of taking part online.

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