 
Summary: JONATHAN BAIN
AGAINST PARTICLE/FIELD DUALITY: ASYMPTOTIC PARTICLE
STATES AND INTERPOLATING FIELDS IN INTERACTING QFT
(OR: WHO'S AFRAID OF HAAG'S THEOREM?)
ABSTRACT. This essay touches on a number of topics in philosophy of quantum field
theory from the point of view of the LSZ asymptotic approach to scattering theory. First,
particle/field duality is seen to be a property of free field theory and not of interacting QFT.
Second, it is demonstrated how LSZ sidesteps the implications of Haag's theorem. Finally,
a recent argument due to Redhead (1995), Malament (1996) and Arageorgis (1995) against
the concept of localized particle states is addressed. Briefly, the argument observes that
the ReehSchlieder theorem entails that correlations between spacelike separated vacuum
expectation values of local field operators are always present, and this, according to the
above authors, dictates against the notion of a localized particle state. I claim that this
moral is excessive and that a coherent notion of localized particles is given by the LSZ
approach. The underlying moral to be drawn from this analysis is that questions concerning
the ontology of interacting QFT cannot be appropriately addressed if one restricts oneself
to the free theory.
0. INTRODUCTION1
Quantum field theory (QFT) is arguably the best confirmed theory known
to physics. (Un)fortunately, it is beset with interpretational difficulties even
