Abstract

Algebraic quantum fields theory (AQFT) is a mathematical framework for studying foundations of QFT where a model is specified in terms of a net of local algebras. The word “locality” has several meanings in this context, including the fact that one assigns these algebras to bounded regions, and that operators localized in spacelike separated regions commute. The need for more general localization arises already in quantum electrodynamics (QED), e.g. in the case of a Dirac string. More generally, I will argue that the natural class of non-local observables arises as relativised observables in the presence of a quantum reference frames (QRF). Such observables describe relations between a local net and a QRF and these are the quantities that we actually measure.