Chunling Yan

The general study of the ontology of quantum field theories (QFTs) concerns whether particles or fields are more fundamental. Both views are well-motivated, although each is subject to some serious criticism. Given that the current versions of the particle interpretation and the field interpretation are not satisfying, I propose a mixed ontology of particles and fields in the framework of QFT. I argue that the ontological question should focus on how to view particles and fields consistently in QFT, provided that they are the natural candidates for the ontology of QFT. In particular, based on this reading, I adopt a functionalist reading of ontology and defend a mixed ontology of QFT. I address a paradigmatic case of the mixed ontology approach: a particle/field duality defined in terms of functional equivalence between particles and fields. Functionalism about ontology provides new insight into resolving the problem of unitarily inequivalent representations, which is one of the major interpretational issues of QFT.

It is generally believed that two rival non-relativistic quantum theories, the realist interpretation of quantum mechanics and Bohmian mechanics, are empirically equivalent. In this paper, I use these two quantum theories to show that it is possible to offer a solution to underdetermination in some local cases, by specifying what counts as relevant empirical evidence in empirical equivalence and underdetermination. I argue for a _domain-sensitive_ approach to underdetermination. Domain sensitivity on theories’ predictions plays a role in determining whether two or more theories are empirically equivalent and underdetermined. To support my argument for the denial of the empirical equivalence between Bohmian mechanics and the realist interpretation of quantum mechanics, I argue that they are not empirically equivalent when we consider their predictions for domains outside their application, using the relativistic domain as an example.

It is difficult to articulate how we should take a realist attitude towards Bohmian mechanics because there are many versions of it. This paper aims to clarify the realist commitments of Bohmian mechanics and how we can understand it from a general scientific realist perspective. I use the box experiment, a double-slit like experiment conducted by Cardone et al. :1–13, 2004; Int J Mod Phys B 20:1107–1121, 2006), as a working example to argue that a causal realist account that is applicable to Bohmian mechanics, has to be supplemented with the use of Inference to the Best Explanation. The reason is because causal realism on its own does not form a sufficient basis for realism about Bohmian mechanics. In particular, I argue that the existence of the pilot wave explains why we observe an anomalous interference effect in the experiment of Cardone et al. The conclusion to draw is that a complete realist account about Bohmian mechanics rests on explanatory considerations.