Understanding Barandes' microscopic theory of causality

[iste]

Most interpretations require some speculative import. But iiuc you are saying this requires some additional contrivance above and beyond other interpretations and I just don't see it.

For example, while the conditional probabilities are sparse, the standalone probabilities are not, and interpreting these epistemically as about a configuration actually existing at all times seems no more burdensome than the myriad of worlds in the MWI or the exotic guiding wave nomology of Bohmian mechanics.

Sure, but the supposed philosopical contribution of the indivisible approach is compromised because you can't say it implies any novel interpretation without begging the question and presupposing that interpretation. If the formalism doesn't specify a trajectory then I can interpret it in anyway I want. Sure, the interpretation isn't refuted but the indivisible formalism doesn't actually contribute anything to or imply the interpretation by itself.

 

[Morbert]

Sure, but the supposed philosopical contribution of the indivisible approach is compromised because you can't say it implies any novel interpretation without begging the question and presupposing that interpretation. If the formalism doesn't specify a trajectory then I can interpret it in anyway I want. Sure, the interpretation isn't refuted but the indivisible formalism doesn't actually contribute anything to or imply the interpretation by itself.

There's no question begging, as the interpretation, like any other interpretation, is presented as an interpretation, not a self-justifying conclusion.

 

[Sambuco]

One can prove that every finite- rank density matrix can be written as a convex combination of projectors, and that every density matrix can be written as the limit of a family of convex combinations of projectors.

Thanks @A. Neumaier! Is this true if we limit ourselves to a single basis? I understand that the work referred to projectors associated with definite configurations.

Lucas.

 

[Sambuco]

There's no question begging, as the interpretation, like any other interpretation, is presented as an interpretation, not a self-justifying conclusion.

I think what @iste points out is interesting and reveals something particular about Barandes' interpretation. It's common to postulate a primitive ontology in $\psi$-ontic interpretations, such as Bohmian mechanics or many-worlds. In those cases, the actual configuration of the system appears explicitly in the equations that define its dynamics. For example, there's the guiding equation that defines the evolution of Bohmian particles. This isn't quite the case in $\psi$-epistemic interpretations, where the ontology is more open to discussion. Barandes' interpretation sits somewhere in between, since it postulates a clear ontology formed by definite positions in configuration space, while the central variable of the formulation is not these configurations themselves, but the evolution over time of the epistemic probabilities associated with them. This means that, as we've already mentioned, the current configuration of the system doesn't influence the evolution of these probabilities.

Lucas.

 

[Morbert]

I think what @iste points out is interesting and reveals something particular about Barandes' interpretation. It's common to postulate a primitive ontology in $\psi$-ontic interpretations, such as Bohmian mechanics or many-worlds. In those cases, the actual configuration of the system appears explicitly in the equations that define its dynamics. For example, there's the guiding equation that defines the evolution of Bohmian particles. This isn't quite the case in $\psi$-epistemic interpretations, where the ontology is more open to discussion. Barandes' interpretation sits somewhere in between, since it postulates a clear ontology formed by definite positions in configuration space, while the central variable of the formulation is not these configurations themselves, but the evolution over time of the epistemic probabilities associated with them. This means that, as we've already mentioned, the current configuration of the system doesn't influence the evolution of these probabilities.

@iste is not merely remarking that the interpretation is peculiar. He is framing it as question begging when instead the microphysical ontology of this interpretation is, as Barandes says, "a speculative metaphysical hypothesis", which are standard ingredients to an interpretation.

 

[Sambuco]

@iste is not merely remarking that the interpretation is peculiar. He is framing it as question begging when instead the microphysical ontology of this interpretation is, as Barandes says, "a speculative metaphysical hypothesis", which are standard ingredients to an interpretation.

Yes, I understand. My comment, somewhat independent of @iste's opinion, is that Barandes' interpretation has the curious characteristic of combining a well-defined ontology with dynamic laws that don't speak directly about it, but only about what each observer can say about it, in the spirit of the Bohr's quote "It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature." I don't think this invalidates the interpretation, of course.

Lucas.