Philosophy of Physics Seminar (Thursday - Week 6, TT23)
Thursday 1 June, 4:30pm
Lecture Room, Radcliffe Humanities
Doreen Fraser (Waterloo): 'Philosophical implications of measurement in QFT'
Measurement theory from non-relativistic quantum mechanics (NRQM) cannot be straightforwardly carried over to relativistic quantum field theory (QFT). The ‘impossible measurement’ scenarios presented by Sorkin and Borsten, Jubb & Kells vividly illustrate that superluminal signalling is a hazard of prima facie reasonable attempts to apply measurement theory from NRQM to relativistic quantum theory. This is one motivation for the recent flurry of research activity devoted to formulating models of measurement for QFT. I will draw out some of the philosophically important implications of this recent work. For concreteness, I will focus on the measurement framework for algebraic QFT recently proposed by Fewster and Verch. The Fewster-Verch measurement framework departs from the traditional operationalist interpretation of AQFT in significant respects. Second, the new state update rules in the Fewster-Verch measurement framework cannot be interpreted as representing a change of state that happens in any region of spacetime. This feature is shared with other recent proposals for modeling measurement in QFT, which suggests that it is a general moral about measurement theories that are suited to relativistic spacetime. This has direct consequences for the form that the Measurement Problem takes in QFT with its measurement theory (compared to NRQM with its measurement theory).
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