Ontology and the foundations of quantum theory.

A brief review of the historical main line of investigation of the ontology of quantum theory is given with an emphasis on elementary particles. Einstein et al. considered possible elements of reality and questioned the completeness of the quantum state, prompting later studies of local causality in relation to their physical properties. Later reconsiderations of quantum mechanical law have involved differing attitudes toward the objective existence not only of the properties of distantly located particles, but even of entire universes of systems including them. Experimental foundational investigations have mainly involved quantum mechanics at low energies but some have begun to explore higher energies, where quantum field theory is required, and its ontology has been seen to involve quantum fields as well as elementary particles. [ABSTRACT FROM AUTHOR]