Travis Norsen

  • Travis Norsen replied to the topic Why Bohmian theory? in the forum Bohm's theory 9 years ago

    Tell me how the following is unfair:

    “Pragmatism is not incompatible with the realist program: but it is flexible enough to make room for alternative programs. Its central insight is that concepts are intellectual tools for coping with the world, and that we can create concepts and use them in a variety of ways in pursuit of our goals. One way…[Read more]

  • Dear Reinhard, I don’t understand what you find “Platonic” about “claiming reality for the particles and their trajectories”. How is this, in principle, any different from the claims that people made in the 19th century about matter being made of atoms?

    You ask: “how would you convince me that we live in such a world?” I guess I would start…[Read more]

  • Travis Norsen replied to the topic Why Bohmian theory? in the forum Bohm's theory 9 years ago

    Hi Richard — I read through your “open_question…” essay last night. I enjoyed reading it, as it contains a very nice collection of quotes from Einstein, Bohr, etc. But I really just don’t get the pragmatic turn you want to take. As I understand it, your pragmatism does not just mean “sometimes we should maybe try things out and see what…[Read more]

  • Ah, so you understand MWI/Everett as what Allori et al call “Sm” in this paper:

    http://arxiv.org/pdf/0903.2211.pdf

    Is that right? I’m still a little confused by how you talk about the ontology, though. Do you think of the m-field as something like an emergent property of the wave function (such that it, the m-field, doesn’t count as an…[Read more]

  • I would be very interested to hear your talk, so do send me a link if it’s recorded, etc. I hear what you are saying about the local density matrices, but presumably you can appreciate that there are further (subtle and challenging) questions. For example, if the local density matrix doesn’t exhaust the ontology, then it is hardly persuasive to…[Read more]

  • Lev, yes, in Bohm’s theory the nonlocality is clear: if you have a pair of entangled particles, the velocity of one of them (according to the theory) can depend on a free choice (say, about some external magnetic field that you might apply) at the location of the other one. That is, something over here (the trajectory of this particle) depends…[Read more]

  • Dear Lev, Two quick (and arguably off-topic) points about your previous comment to me above (#2744).

    First, you seem to be using the word “beable” to mean something like “hidden variable” (i.e., stuff postulated to exist in addition to the wave function). I understand Bell’s term in a different way, though — as referring to whatever a theory…[Read more]

  • Hi Dustin. I read some earlier version of your paper about this a year or so ago (probably when it appeared on arxiv or something??). I found it interesting but now don’t remember the details. Your comments above motivate me to want to understand it better, so I’ll try to take a look at the paper you posted on this thread (which I haven’t…[Read more]

  • Hi Lev, Thanks for the elaboration/clarification. I think we agree, about two things. First, yes, this setup probably should not be described as “counterfactual communication” according to Bohm’s theory since *something* (the empty wave) goes along the path through 1/2 and then causally influences the motion of the Bohmian particle below. And…[Read more]

  • Hi Nathan and Dustin —

    Nathan, when I read this paragraph…

    “I was also dismayed by the fact that retrocausation had been charaterized as conspiratorial (when I learned about it). Clearly, those who adopt this charaterization are taking the causal arrow of time for granted. Apparently their intuition is so firmly grounded in the macroscopic…[Read more]

  • Travis Norsen replied to the topic Why Bohmian theory? in the forum Bohm's theory 9 years ago

    That helps a little, but I remain confused. You say that particles (for example) exist, but that the function of the mathematical objects we use to characterize them (wave functions, etc.) “is not descriptive but prescriptive”. OK, sure — but then how *can* one (literally, accurately, and completely) describe these particles (if I should even…[Read more]

  • Hi Lev, Thanks for this interesting contribution to the forum. I didn’t follow the controversy in your Refs [1-5] so perhaps I’m just ignorant of the context and hence missing the point. But my initial impression is that the whole question here is based on a kind of equivocation on the word “particle”. You define “counterfactual communication”…[Read more]

    • Dear Travis,
      Of course, communication with a water wave, or with a classical electromagnetic wave is not counterfactual. What I felt is that some Bohmians do not take quantum wave, and especially empty wave, in a strong ontological sense. Wave is a part of a physical law which governs particle motion. My guiding principle of the presence of a…[Read more]

  • Dustin wrote: “there seems to be a misunderstanding”.

    That is my sense as well. Reinhard, it seems like you have a number of simple factual misconceptions about how Bohm’s theory works and what it says. Did you read the long comment on the other thread that I linked to above? If you have questions about how/why/whether the sorts of things I…[Read more]

  • Travis Norsen replied to the topic Why Bohmian theory? in the forum Bohm's theory 9 years ago

    Hi Richard, I read your post several times trying to understand your point of view, but I’m still just not sure what you mean to be saying. Can you, for lack of a better phrase, dumb it down for me a bit? It sounds like you’re saying that, according to “observer-free quantum theory”, the ontology (i.e., the stuff that really exists physically…[Read more]

  • Just briefly, re: the point that an “energy measurement” (of the sort discussed above) doesn’t reveal the true pre-measurement energy of the particle… First, I don’t think it’s even clear what the true pre-measurement energy of the particle would be, according to Bohm’s theory. There is, in some sense, no such dynamically meaningful property…[Read more]

  • Thanks, Werner, for your contribution — and thanks, Dustin, for your comments (which I agree with completely). I wrote some comments in response to Richard Healey’s contribution over on this other thread:

    Comments on Bohmian mechanics

    Basically I was there echoing/elaborating what Dustin expressed by noting…[Read more]

  • Richard, thank you for your stimulating contribution. I think you raise a number of extremely important points (that overlap with the issues raised by Reinhard Werner and Shelly Goldstein and by implication Max Schlosshauer). Of course I don’t really agree with your conclusion (that Bohm’s theory is plagued by a number of…[Read more]

  • Hi Ken, I’m not really sure what needs explaining here. I mean, one should really understand (“orthodox”??) Bohmian mechanics as a theory of the entire universe, whose ontology is (a) all of the particle positions and (b) a single universal wave function evolving according to Schroedinger’s equation. And that universal wave function, to be…[Read more]

  • Hi Daniel, I don’t agree with the claim that “retrocausality is intrinsic to QM” — if that means that any viable quantum theory has to involve backwards in time causation. I made some comments about this over in the “Bohm’s theory” forum (somewhat directly in response to your comments above and the earlier paper they refer to, but also as a way…[Read more]

  • Travis Norsen replied to the topic in the forum Travis Norsen 9 years ago

    So… Rohrlich’s argument that “retro-causality is intrinsic to QM”. For some details, see Section II of Rohrlich’s paper “A reasonable thing that just might work”, which is here:

    http://physweb.bgu.ac.il/~rohrlich/Bell50titles.pdf

    The basic idea is as follows. Consider three people, Alice, Bob, and Jim, who share a bunch of GHZ-state…[Read more]

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