I meant the second. If that is the point of the papers, then I guess that’s fair enough, but, well, I don’t anticipate that their argument is going to be valid. I’ll go and read it; no need to summarize.
First paper,
The trouble with all these interpretations [Bohm, spontaneous collapse, WMI] as quick fixes for Bell’s hard-edged remark is that they look to be just that, really quick fixes.
I recognize that this is subjective and fuzzy, but… no? Bohm looks like an incredibly… well, I won’t get into that, but it doesn’t seem to me like a quick fix. Spontaneous collapse, okay, I grant that one. MWI doesn’t seem like a quick fix in any sense either.
Their world purports to have no observers, but then it has no probabilities ei- ther. What are we then to do with the Born Rule for calculating quantum probabilities? Throw it away and say it never mattered?
No, that’s silly.
It is true that quite an effort has been made by the Everettians to rederive the rule from decision theory.
Yes, that was silly. But that’s hardly the strongest argument that could or has been made. You don’t get to pick your opponents’ arguments like that. The way Decision theory is used when I’ve seen it is: any structure which is formally equivalent to a decider is a decider, and QM has such structures.
No amount of sophistry can make “decision” anything other than a hollow concept in a predetermined world.
… No, that’s stupid. No amount of sophistry can make predetermination relevant to the meaningfulness of ‘decision’. And of course the relevance of this argument is dependent on taking the argument for probability-in-MWI to be strictly dependent on the applicability of decision theory in a particular way which is not the way it’s actually being used. In particular, by the time you ascend the level of abstraction enough for decision theory to be relevant, you’re past the point at which predetermination has fallen away and you’re dealing with an effectively non-predetermined system.
And then he just goes off and makes an argument that the theory is information about the state, not the state itself. But… … … if it successfully models your information about a thing, then the thing acts consistently with the model, which means you’re also modeling the thing. There are theorems that constrain the ontology given these observations, and it basically boils down to ‘QM is super legit’.
I agree with you up until your last paragraph: the strength of Fuchs’ papers are not in their direct criticism of Everettian interpretations (Kent’s papers are a lot better at that).
For your last paragraph, I think Fuchs would take umbrage at the idea that you are necessarily “modeling the thing” when you assign a quantum state to a given system. I don’t think he believes that systems have a “true ontic state” of which quantum states are representative. Rather, the quantum state is merely a representation of an agent’s beliefs about the future outcomes of their interventions/measurements into the universe. Nevertheless, Fuchs claims to be a scientific realist.
I’m deliberately using the word “think” a lot here because I’m not confident of relaying Fuchs’ views faithfully (this isn’t directly my area of research). I haven’t adopted a QBist interpretation (or any other), but from what I’ve read I feel it’s worth serious discussion.
You also mentioned theorems constraining ontology. You may be interested in Fuchs’ take on Bell’s Theorem: http://arxiv.org/pdf/1311.5253v1.pdf . I have been to a talk where he explains why the PBR theorem doesn’t impact his interpretation, although the details evade me (and I can’t find anything written about it by him online).
I’m not sure how to interpret your question.
If you’re asking:
“What is the case against the MWI interpretation of quantum theory?”
then I would probably cite difficulties in explaining why our branch’s history appears to be Born-rule typical as a major argument.
If instead you’re asking:
“What is the case for a non-ontological interpretation of the wavefunction?”
then the best I can do is attempt to summarise the arguments put forth in the above papers.
I meant the second. If that is the point of the papers, then I guess that’s fair enough, but, well, I don’t anticipate that their argument is going to be valid. I’ll go and read it; no need to summarize.
First paper,
I recognize that this is subjective and fuzzy, but… no? Bohm looks like an incredibly… well, I won’t get into that, but it doesn’t seem to me like a quick fix. Spontaneous collapse, okay, I grant that one. MWI doesn’t seem like a quick fix in any sense either.
No, that’s silly.
Yes, that was silly. But that’s hardly the strongest argument that could or has been made. You don’t get to pick your opponents’ arguments like that. The way Decision theory is used when I’ve seen it is: any structure which is formally equivalent to a decider is a decider, and QM has such structures.
… No, that’s stupid. No amount of sophistry can make predetermination relevant to the meaningfulness of ‘decision’. And of course the relevance of this argument is dependent on taking the argument for probability-in-MWI to be strictly dependent on the applicability of decision theory in a particular way which is not the way it’s actually being used. In particular, by the time you ascend the level of abstraction enough for decision theory to be relevant, you’re past the point at which predetermination has fallen away and you’re dealing with an effectively non-predetermined system.
And then he just goes off and makes an argument that the theory is information about the state, not the state itself. But… … … if it successfully models your information about a thing, then the thing acts consistently with the model, which means you’re also modeling the thing. There are theorems that constrain the ontology given these observations, and it basically boils down to ‘QM is super legit’.
I agree with you up until your last paragraph: the strength of Fuchs’ papers are not in their direct criticism of Everettian interpretations (Kent’s papers are a lot better at that).
For your last paragraph, I think Fuchs would take umbrage at the idea that you are necessarily “modeling the thing” when you assign a quantum state to a given system. I don’t think he believes that systems have a “true ontic state” of which quantum states are representative. Rather, the quantum state is merely a representation of an agent’s beliefs about the future outcomes of their interventions/measurements into the universe. Nevertheless, Fuchs claims to be a scientific realist.
I’m deliberately using the word “think” a lot here because I’m not confident of relaying Fuchs’ views faithfully (this isn’t directly my area of research). I haven’t adopted a QBist interpretation (or any other), but from what I’ve read I feel it’s worth serious discussion.
You also mentioned theorems constraining ontology. You may be interested in Fuchs’ take on Bell’s Theorem: http://arxiv.org/pdf/1311.5253v1.pdf . I have been to a talk where he explains why the PBR theorem doesn’t impact his interpretation, although the details evade me (and I can’t find anything written about it by him online).