Towards an objective quantum physics

Donald Bedford, Derek Wang

Richard Healey

Measurement outcomes provide data for a physical theory. Unless they are objective they support no objective scientific knowledge. So the outcome of a quantum measurement must be an objective physical fact. But recent arguments purport to show that if quantum theory is universally applicable then there is no such fact. This calls for a reappraisal of the notions of fact and objectivity. If quantum theory is universally applicable the facts about the physical world include a fact about each quantum measurement outcome. These physical facts lack an ideal kind of objectivity but their more modest objectivity is all that science needs.

C. L. Herzenberg

During the last few years, several studies have proposed the existence of a threshold separating classical from quantum behavior of objects that is dependent on the size and mass of an object as well as being dependent on certain properties usually associated with the universe as a whole. Here, we reexamine the results of these studies and recast the threshold criteria in terms of a critical threshold value for the moments of inertia of physical objects. Physical objects having moments of inertia above this critical threshold value would be expected to behave necessarily in a classical manner in terms of their center of mass motion as entire objects, while physical objects having moments of inertia lower than this threshold value could exhibit quantum behavior unless brought into classicality by other effects. A comparison with observed values of moments of inertia is presented, and the moment of inertia is suggested as a classifying parameter for examination of the quantum versus classical behavior of objects in the mesoscale domain.

Alberto C. de la Torre

Michaël Esfeld

As far as classical physics is concerned, it is possible to trace causal relations between physical objects (i.e. particles in this case) back to intrinsic properties of these objects (such as their mass and charge). On this view, causal relations turn out to be internal instead of external relations, supervening on intrinsic properties of the relata (as proposed by Heil and Lowe). However, one can raise doubts about this view already in Newtonian mechanics. The decisive blow to this view comes from quantum physics, with Bell’s theorem proving that no dynamics based on local, intrinsic properties of quantum objects can yield the empirical predictions of quantum mechanics. Nonetheless, quantum entanglement by no means implies that we have to abandon an ontology of objects (i.e. substances such as particles) in favour of an ontology of structures (as claimed by French and Ladyman). Any of the known proposals for a quantum ontology of matter in space-time is committed to objects. However, on any of these proposals, what determines the dynamics of these objects are not local, intrinsic properties, but a global or holistic property instantiated by all the objects together – that is, a structure that takes all the objects in the universe as its relata. The view set out in this paper thus amounts to combining ontic structural realism with an ontology of objects that can be conceived as substances. This suggestion is illustrated by drawing on the ontology of quantum physics worked out by Bohm and Bell. 1.

Inge Svein Helland