The Wallstrom objection as a possibility to augment quantum theory

Abstract

Wallstrom has argued that quantum interpretations which construct the wave function starting from Madelung variables $\psi(q)=\rho(q)\exp(\frac{i}{\hbar}S(q))$, in particular, many variants of Nelsonian stochastics, are not equivalent to quantum theory. Accepting this, we explicitly add the physical restriction $(\forall q\in Q)|\psi(q)|^2>0$ in the configuration space representation to quantum theory. The resulting theories depend on the choice of the configuration space $Q$. The restriction adds possibilities to falsify such theories, making them preferable following Popper's criterion of empirical content until they have been really falsified. Considering the case of a relativistic scalar field, we argue that it is reasonable to expect that the variant based on particle ontology can be (or even has been already) falsified, while to falsify the variant based on field ontology seems much harder, if not impossible. If correct, switching to a field ontology seems a reasonable choice for interpretations based on Madelung variables to circumvent the Wallstrom objection.