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Ken Wharton replied to the topic Causality and quantum mechanics (Online 7/15 @ 10 p.m. to Midnight UTC-7) in the forum Retrocausal theories 8 years, 8 months ago
Hi David and Matt,
Apologies for taking so long to get to this very interesting piece! Some notes:
– This is probably my own personal bias showing, but at the end of the first column, I thought at first that you were talking about running the experiment in two different time-directions. So you might help people like me here if you just note…[Read more]
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Ken Wharton replied to the topic Holism and time symmetry in the forum Retrocausal theories 8 years, 8 months ago
Yes, I agree with that last bit. It’s been ages since I’ve read that paper of yours, and I still have a few here I’d like to get to first, but thanks for reminding me about it; I’ll check it out soon with all this in mind!
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Ken Wharton replied to the topic Retrocausation vs Retrodiction in the forum Retrocausal theories 8 years, 8 months ago
Hi Bob,
Thanks for your detailed response… I do think we almost have exactly the same perspective about how to make sense of these very experiments. So it’s interesting that I see this perspective as retrocausal, while you merely see it as retrodictive. Let me try once more to see if I can figure out exactly where this divergence comes…[Read more]
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Ken Wharton replied to the topic Holism and time symmetry in the forum Retrocausal theories 8 years, 8 months ago
Hi Peter,
I guess I mis-read what you were doing here… But given your clarification, I think you should be careful about simply assigning the outcome of the future measurement as a hidden variable. Huw has already talked about exactly this kind of minimal-ontology (see section 5.2 of 1002.0906 ), and the obvious downside is that such accounts…[Read more]
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Ken Wharton replied to the topic Are retrocausal accounts of entanglement unnaturally fine-tuned? in the forum Retrocausal theories 8 years, 8 months ago
Hi Nathan,
You’re precisely right that the issue of “not remembering the future” is entropy-related, and it’s just as true for machines as it is for humans. I’m fine with taking humans out of the equation.
And given this connection, I suppose it doesn’t make sense to imagine time-reversing the direction one remembers things without also…[Read more]
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Ken Wharton replied to the topic Holism and time symmetry in the forum Retrocausal theories 8 years, 8 months ago
Hi Peter,
Nice paper! Yes, I think you got the SEPRB example just about right… As you note, we didn’t really commit to an intermediate ontology, so that’s where things get tricky, but even without committing to a particular ontology I think you’re perfectly justified in making your conclusions.
Still, since I’m quite interested in the pros…[Read more]
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Ken Wharton replied to the topic General "Block Universe" Discussion in the forum Retrocausal theories 8 years, 8 months ago
Mark: No, I’ve never been able to make sense of the Transactional Interpretation in a block-universe context… I know John Cramer is aiming to reduce entangled states to coupled-single-particle states, which would certainly help, but I haven’t seen a mathematical framework for how he hopes to do this. Even in the single-particle case, I’m not…[Read more]
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Ken Wharton replied to the topic Retrocausation vs Retrodiction in the forum Retrocausal theories 8 years, 8 months ago
Thanks, Bob, for raising an excellent and important issue!
I’m fine with your definition of retrodiction.
On your definition of “retrocausality”, since I’m a block universe fan, I’m always pouncing on phrases like “alter the past” as meaningless: Any event in spacetime is what it is, and can’t “change” or “be altered”. (Just as you describe…[Read more]
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Ken Wharton replied to the topic General "Block Universe" Discussion in the forum Retrocausal theories 8 years, 8 months ago
Hi Bob,
I agree with Mark that you have the right idea for a Block Universe, but Mark’s last paragraph doesn’t really address the key questions in that last paragraph of yours. (Mark: I would say that the whole point of the Block Universe is that everything ontological can be described “all-at-once”, so mentioning all of these different…[Read more]
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Ken Wharton replied to the topic Are retrocausal accounts of nonlocality conspiratorial? A toy model. in the forum Retrocausal theories 8 years, 8 months ago
Hi Dustin,
Very interesting paper! It was very useful to read for a fuller account of your views, after only seeing your presentation in Cambridge last summer.
Some thoughts that occurred to me as I read through the paper:
– After using time-symmetry as a motivation for this general style of approach, I was surprised to see (3) in your model…[Read more]
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Ken Wharton replied to the topic General "Block Universe" Discussion in the forum Retrocausal theories 8 years, 8 months ago
Taking off my moderator’s hat, maybe I can immoderately kickstart this discussion with Section IV of my latest FQXi essay. In that section I defend the block universe perspective, while also noting that some of our intuitions might be incorrectly biased against it.
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Ken Wharton replied to the topic Thinking about QM as a variational principle (online 7/9 @ 9am UTC-6) in the forum Retrocausal theories 8 years, 8 months ago
Hi Alan,
Sorry it took me so long to get back here…
On the joint-probability issue, I see two ways to go. In my first response, way above, I mentioned that one also needs the rule that tells one how to figure out which allowed outcomes correspond to which measurement settings/geometries. I would think that this rule would solve the problem…[Read more]
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Ken Wharton started the topic General "Block Universe" Discussion in the forum Retrocausal theories 8 years, 8 months ago
I’ve seen the issue of whether or not to adopt a “block universe” perspective come up in at least a half-dozen different contexts here, so I thought it might be useful to start a new topic. All interested parties can now have a common place to discuss this crucial issue.
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Ken Wharton replied to the topic A Relativistic Symmetrical Interpretation of the Dirac Equation in (1+1) D (online 7/9 @ 11pm UTC-7) in the forum Retrocausal theories 8 years, 8 months ago
Hmmm… You *are* using this (phi* psi ) to generate probabilities, right? After all , that’s generally what one does with “amplitudes”; squares them and turns them into probabilities. Maybe you need a different terminology if that’s not what you’re going for.
As for “reality”, I meant “ontic”; complex/real is a totally different issue from…[Read more]
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Ken Wharton replied to the topic Explicit models of retrocausation in the forum Retrocausal theories 8 years, 8 months ago
Hi Nathan,
I’m still meaning to get to the “Stochastic Quantization” literature you mentioned, but I did look at your summary of it, and I’m a bit concerned about this “extra” time dimension you noted in a footnote. (Some discussion of “meta-time” has also recently come up in Cohen’s topic and Elitzur’s topic, and I hope to get a broader…[Read more]
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Ken Wharton replied to the topic Quantum causal models, faithfulness and retrocausality (onl. 7/16 @ 11pm UTC+10) in the forum Retrocausal theories 8 years, 8 months ago
Hi Pete,
Thanks for this interesting and useful paper! I like the changes in 4.3 that I noticed from the original version, concerning how the final boundaries are implemented. And of course there’s a lot of connection between our papers here; the “internally cancelling paths” you refer to has got to be due to some *symmetry*, wouldn’t you…[Read more]
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Ken Wharton replied to the topic A Relativistic Symmetrical Interpretation of the Dirac Equation in (1+1) D (online 7/9 @ 11pm UTC-7) in the forum Retrocausal theories 8 years, 8 months ago
Hi Michael; Thanks for your response, but I’m not sure how to interpret a probability for an experiment after it already has a known outcome.
Let me ask it this way. Suppose the experiment is *complete*, in that I know the precise outcome, and I’m looking back on the whole transaction and doing my best to describe what really happened. At this…[Read more]
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Ken Wharton replied to the topic On the single-particle Bohmian account in the forum Bohm's theory 8 years, 8 months ago
Hi Travis,
Thanks for the thoughtful response! You’re right that not much “needs explaining” concerning my original concern, and your last bit is a good point (where you point out that later position measurements can be used to measure other non-position quantities at earlier times). It somewhat bothers me that (say) the energy measured in such…[Read more]
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Ken Wharton replied to the topic Are retrocausal accounts of entanglement unnaturally fine-tuned? in the forum Retrocausal theories 8 years, 8 months ago
Hi Nathan; Thanks for the catch on the occasional misuse of the phrase “Tsirelson Bound”… That’s an easy fix, at least!
On the more substantive issues, I do think that it will turn out that symmetry will play the main no-signaling role for even partially entangled states. You’re right that some of the symmetries will disappear in those cases,…[Read more]
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Ken Wharton replied to the topic A Relativistic Symmetrical Interpretation of the Dirac Equation in (1+1) D (online 7/9 @ 11pm UTC-7) in the forum Retrocausal theories 8 years, 8 months ago
Hi Michael,
Thanks for your paper… I’m a bit confused about the proposed ontology; what’s really happening between the measurements, in this account? Aharonov’s take on the two-state-vector formalism seems to be that both the pre-selected wavefunction and the post-selected wavefunction are “really there”. But you don’t seem to be saying the…[Read more]
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