Abstract
Ideal measurements in quantum mechanics can be described formally as instantaneous changes of the state vector or, more generally, of the density matrix . By its lack of covariance, this formalism is not very adequate for relativistic quantum theories such as local field theory. For the latter, we propose a modified formalism, according to which a field measurement in a space-time region changes the field state in the future and side cone of . This proposal is justified by physical considerations.
- Received 25 February 1969
DOI:https://doi.org/10.1103/PhysRevD.1.566
©1970 American Physical Society