|
Post by Eva Yojimbo on Jun 18, 2017 11:22:32 GMT
I'm saying it's still unclear to scientists what the Schrodinger equation means ontologically, hence one reason for the differing interpretations. Okay, but above you'd said the equation is deterministic. You're saying that it's deterministic in some non-ontological sense? What in the world would that even mean? Yes, if you just take the equation at face value it's deterministic. "At face value" means you aren't changing it by adding a stochastic collapse. You have to change what it fundamentally is in order to make it ontologically probabilistic. Sean Carroll summed this up nicely in an article. I'll quote the relevant bits: "The “anger” strategy says “I hate the idea of... (an ontologically real wavefunction) with such a white-hot passion that I will change the rules of quantum mechanics in order to avoid them.” And people do this! In the four options listed here, both dynamical-collapse theories and hidden-variable theories are straightforward alterations of the conventional picture of quantum mechanics. In dynamical collapse, we change the evolution equation, by adding some explicitly stochastic probability of collapse. In hidden variables, we keep the Schrödinger equation intact, but add new variables — hidden ones, which we know must be explicitly non-local. Of course there is currently zero empirical evidence for these rather ad hoc modifications of the formalism, but hey, you never know."
|
|
|
Post by Terrapin Station on Jun 18, 2017 11:27:19 GMT
Okay, but above you'd said the equation is deterministic. You're saying that it's deterministic in some non-ontological sense? What in the world would that even mean? Yes, if you just take the equation at face value it's deterministic. "At face value" means you aren't changing it by adding a stochastic collapse. You have to change what it fundamentally is in order to make it ontologically probabilistic. Sean Carroll summed this up nicely in an article. I'll quote the relevant bits: "The “anger” strategy says “I hate the idea of... (an ontologically real wavefunction) with such a white-hot passion that I will change the rules of quantum mechanics in order to avoid them.” And people do this! In the four options listed here, both dynamical-collapse theories and hidden-variable theories are straightforward alterations of the conventional picture of quantum mechanics. In dynamical collapse, we change the evolution equation, by adding some explicitly stochastic probability of collapse. In hidden variables, we keep the Schrödinger equation intact, but add new variables — hidden ones, which we know must be explicitly non-local. Of course there is currently zero empirical evidence for these rather ad hoc modifications of the formalism, but hey, you never know." What's non-ontologically deterministic?
|
|
|
Post by Eva Yojimbo on Jun 18, 2017 11:42:32 GMT
Yes, if you just take the equation at face value it's deterministic. "At face value" means you aren't changing it by adding a stochastic collapse. You have to change what it fundamentally is in order to make it ontologically probabilistic. Sean Carroll summed this up nicely in an article. I'll quote the relevant bits: "The “anger” strategy says “I hate the idea of... (an ontologically real wavefunction) with such a white-hot passion that I will change the rules of quantum mechanics in order to avoid them.” And people do this! In the four options listed here, both dynamical-collapse theories and hidden-variable theories are straightforward alterations of the conventional picture of quantum mechanics. In dynamical collapse, we change the evolution equation, by adding some explicitly stochastic probability of collapse. In hidden variables, we keep the Schrödinger equation intact, but add new variables — hidden ones, which we know must be explicitly non-local. Of course there is currently zero empirical evidence for these rather ad hoc modifications of the formalism, but hey, you never know." What's non-ontologically deterministic? I don't get why you're asking this. I haven't said anything about non-ontological determinism. Science generally considers something deterministic if its future state can be completely predicted from a prior state, generally done via mathematical modeling and empirical confirmation. The wavefunction models particles in this way, saying that particles are in multiple states (superpositioned), and we can empirically see it in, eg, the double-slit experiment. It requires interpreting those multiple states as non-real, non-ontological, in order to make it probabilistic. If you're going to go down this road, you could just as easily argue that General Relativity isn't ontologically deterministic since we can just interpret everything it models as non-real too.
|
|
|
Post by faustus5 on Jun 18, 2017 11:56:38 GMT
It requires interpreting those multiple states as non-real, non-ontological, in order to make it probabilistic. If you're going to go down this road, you could just as easily argue that General Relativity isn't ontologically deterministic since we can just interpret everything it models as non-real too. So do you endorse mathematical Realism, or are you just setting out the possible positions one can take? Because from my perspective as a pragmatist, believing that the wave function is real is not a default position which everyone is expected to start from, with those who reject its reality "adding something" or being particularly ideological. Mathematical Realism is itself ideological, a choice one makes independent of the results one gets from just doing the calculations and checking their results against measured reality.
|
|
|
Post by Eva Yojimbo on Jun 18, 2017 13:21:02 GMT
It requires interpreting those multiple states as non-real, non-ontological, in order to make it probabilistic. If you're going to go down this road, you could just as easily argue that General Relativity isn't ontologically deterministic since we can just interpret everything it models as non-real too. So do you endorse mathematical Realism, or are you just setting out the possible positions one can take? Because from my perspective as a pragmatist, believing that the wave function is real is not a default position which everyone is expected to start from, with those who reject its reality "adding something" or being particularly ideological. Mathematical Realism is itself ideological, a choice one makes independent of the results one gets from just doing the calculations and checking their results against measured reality. I'm primarily setting out the possible positions one can take. Just to be clear, when I'm talking about the ontology of the wave function I'm really talking about the ontology of what it's modeling: the superpositioned state of particles. This doesn't require mathematical realism, and really what collapse and psi-epistemic theories are denying is the ontology of what the wave function models. IE, when you shine a light at a double-slit and see a wave-pattern, Copenhagen and quantum Bayesians would say that state of the particle isn't real (technically, QBisms would probably say they're agnostic on its reality-state). Sean Carroll also covered this when he talked about quantum Bayesianism: "The “denial” strategy says “The idea of... (an ontologically real wave function) is so profoundly upsetting to me that I will deny the existence of reality in order to escape having to think about it.” Advocates of this approach don’t actually put it that way, but I’m being polemical rather than conciliatory in this particular post. And I don’t think it’s an unfair characterization. This is the quantum Bayesianism approach, or more generally “psi-epistemic” approaches. The idea is to simply deny that the quantum state represents anything about reality; it is merely a way of keeping track of the probability of future measurement outcomes. Is the particle spin-up, or spin-down, or both? Neither! There is no particle, there is no spoon, nor is there the state of the particle’s spin; there is only the probability of seeing the spin in different conditions once one performs a measurement." Though QBism isn't violating Occam, it does seem rather silly to me. Collapse models like Copenhagen, however, are fundamentally altering the basic formalism by adding stochastic collapse.
|
|
|
Post by faustus5 on Jun 18, 2017 13:27:17 GMT
|
|
|
Post by jillmcbain on Jun 18, 2017 13:31:23 GMT
So do you endorse mathematical Realism, or are you just setting out the possible positions one can take? Because from my perspective as a pragmatist, believing that the wave function is real is not a default position which everyone is expected to start from, with those who reject its reality "adding something" or being particularly ideological. Mathematical Realism is itself ideological, a choice one makes independent of the results one gets from just doing the calculations and checking their results against measured reality. I'm primarily setting out the possible positions one can take. Just to be clear, when I'm talking about the ontology of the wave function I'm really talking about the ontology of what it's modeling: the superpositioned state of particles. This doesn't require mathematical realism, and really what collapse and psi-epistemic theories are denying is the ontology of what the wave function models. IE, when you shine a light at a double-slit and see a wave-pattern, Copenhagen and quantum Bayesians would say that state of the particle isn't real (technically, QBisms would probably say they're agnostic on its reality-state). Sean Carroll also covered this when he talked about quantum Bayesianism: "The “denial” strategy says “The idea of... (an ontologically real wave function) is so profoundly upsetting to me that I will deny the existence of reality in order to escape having to think about it.” Advocates of this approach don’t actually put it that way, but I’m being polemical rather than conciliatory in this particular post. And I don’t think it’s an unfair characterization. This is the quantum Bayesianism approach, or more generally “psi-epistemic” approaches. The idea is to simply deny that the quantum state represents anything about reality; it is merely a way of keeping track of the probability of future measurement outcomes. Is the particle spin-up, or spin-down, or both? Neither! There is no particle, there is no spoon, nor is there the state of the particle’s spin; there is only the probability of seeing the spin in different conditions once one performs a measurement." Though QBism isn't violating Occam, it does seem rather silly to me. Collapse models like Copenhagen, however, are fundamentally altering the basic formalism by adding stochastic collapse. Yay! Eva is back! Where were you? I missed you. imdb2.freeforums.net/thread/33157/ot-utterly-beautiful?page=1&scrollTo=496379
|
|
|
Post by Eva Yojimbo on Jun 18, 2017 14:06:08 GMT
Thanks for the link. I'll try to read ASAP. FWIW, I'm not sure if I'd call any interpretation more pragmatic than the others. The all rely on the same math and arrive at the same empirical results. If Everett or Copenhagen or QBism were proved right tomorrow, it wouldn't alter the work that experimental physicists are doing one iota. That's where the whole "shut up and calculate" mantra came from (though I'm sure Einstein would've disapproved).
|
|
|
Post by Eva Yojimbo on Jun 18, 2017 14:08:11 GMT
I'm primarily setting out the possible positions one can take. Just to be clear, when I'm talking about the ontology of the wave function I'm really talking about the ontology of what it's modeling: the superpositioned state of particles. This doesn't require mathematical realism, and really what collapse and psi-epistemic theories are denying is the ontology of what the wave function models. IE, when you shine a light at a double-slit and see a wave-pattern, Copenhagen and quantum Bayesians would say that state of the particle isn't real (technically, QBisms would probably say they're agnostic on its reality-state). Sean Carroll also covered this when he talked about quantum Bayesianism: "The “denial” strategy says “The idea of... (an ontologically real wave function) is so profoundly upsetting to me that I will deny the existence of reality in order to escape having to think about it.” Advocates of this approach don’t actually put it that way, but I’m being polemical rather than conciliatory in this particular post. And I don’t think it’s an unfair characterization. This is the quantum Bayesianism approach, or more generally “psi-epistemic” approaches. The idea is to simply deny that the quantum state represents anything about reality; it is merely a way of keeping track of the probability of future measurement outcomes. Is the particle spin-up, or spin-down, or both? Neither! There is no particle, there is no spoon, nor is there the state of the particle’s spin; there is only the probability of seeing the spin in different conditions once one performs a measurement." Though QBism isn't violating Occam, it does seem rather silly to me. Collapse models like Copenhagen, however, are fundamentally altering the basic formalism by adding stochastic collapse. Yay! Eva is back! Where were you? I missed you. imdb2.freeforums.net/thread/33157/ot-utterly-beautiful?page=1&scrollTo=496379I was just busy with real-life stuff and wasn't spending much time online. I'm still not sure if I'm "back" in terms of being a regular again. We'll see how it goes. Nice to know I was missed, though (and thanks for the link; that's a lovely piece!).
|
|
|
Post by jillmcbain on Jun 18, 2017 14:13:17 GMT
I was just busy with real-life stuff and wasn't spending much time online. I'm still not sure if I'm "back" in terms of being a regular again. We'll see how it goes. Nice to know I was missed, though (and thanks for the link; that's a lovely piece!). Show up from time to time. You know I love reading your stuff.
|
|
|
Post by general313 on Jun 18, 2017 18:21:23 GMT
There does seem to be experimental evidence that quantum entanglement entails "spooky something at a distance". www.sciencenews.org/blog/context/entanglement-spooky-not-action-distanceAlso quantum computing derives its power from the superposition of states in the qubits, which suggests that the superposition is not just a measurement limitation but something real happening in the physical components of the computer. I'm not saying that this settles anything about hard determinism but I also don't think Occam is leaning toward determinism. Yes, they entail spooky action at a distance under the Copenhagen interpretation, which is a crucial point that the vast majority of such articles leave out. If anything, the closing of the Bell loopholes is more reason to ditch collapse interpretations all together since this will mean QM being fundamentally incompatible with General Relativity. Einstein was right to question collapse interpretations, but was wrong about the reasons why. He thought there were hidden variables, but Bells Theorem (and the continued closing of the Bell loopholes) is ruling out hidden variables as a possible explanation. What you say about quantum computing is correct, but the reality of the superposition is precisely what Copenhagen (and most indeterministic interpretations) dispute. If superposition is real and applies at all levels, then that's when you get determinism, because it means the Shrodinger Wave Equation applies at all levels. There's no doubt that Occam favors determinism because the simplest interpretation of QM is to take the Shrodinger Wave Equation at face value, as an accurate representation of something that's real. If you do that you get determinism, even though we can never measure/experience it as in classical physics. I don't see how you can come to that conclusion. Superposition collapse is by all accounts random, and depending on the outcome will produce different effects on the physical world (regardless of how "real" or "unreal" the superposition is). How can that random element be compatible with determinism?
|
|
|
Post by Eva Yojimbo on Jun 18, 2017 18:57:25 GMT
Yes, they entail spooky action at a distance under the Copenhagen interpretation, which is a crucial point that the vast majority of such articles leave out. If anything, the closing of the Bell loopholes is more reason to ditch collapse interpretations all together since this will mean QM being fundamentally incompatible with General Relativity. Einstein was right to question collapse interpretations, but was wrong about the reasons why. He thought there were hidden variables, but Bells Theorem (and the continued closing of the Bell loopholes) is ruling out hidden variables as a possible explanation. What you say about quantum computing is correct, but the reality of the superposition is precisely what Copenhagen (and most indeterministic interpretations) dispute. If superposition is real and applies at all levels, then that's when you get determinism, because it means the Shrodinger Wave Equation applies at all levels. There's no doubt that Occam favors determinism because the simplest interpretation of QM is to take the Shrodinger Wave Equation at face value, as an accurate representation of something that's real. If you do that you get determinism, even though we can never measure/experience it as in classical physics. I don't see how you can come to that conclusion. Superposition collapse is by all accounts random, and depending on the outcome will produce different effects on the physical world (regardless of how "real" or "unreal" the superposition is). How can that random element be compatible with determinism? Right, the collapse is random. Remove the assumption of collapse and you remove the randomness. The reason the appearance of such randomness is compatible with determinism is most easily explained in an analogy I made in responding to Terrapin Station in my post here: imdb2.freeforums.net/post/549133/thread
|
|
|
Post by general313 on Jun 18, 2017 22:08:35 GMT
I don't see how you can come to that conclusion. Superposition collapse is by all accounts random, and depending on the outcome will produce different effects on the physical world (regardless of how "real" or "unreal" the superposition is). How can that random element be compatible with determinism? Right, the collapse is random. Remove the assumption of collapse and you remove the randomness. The reason the appearance of such randomness is compatible with determinism is most easily explained in an analogy I made in responding to Terrapin Station in my post here: imdb2.freeforums.net/post/549133/thread Your analogy seems backwards to me. The supposed collapse is more like a merging of paths, but your analogy involves forking. Regardless of that though, a quantum computer algorithm would derive an answer that is a statistical summation of the superpositions, so it should in theory always produce a predictable answer. I'll have to do more reading on this.
|
|
|
Post by Eva Yojimbo on Jun 18, 2017 22:47:16 GMT
Right, the collapse is random. Remove the assumption of collapse and you remove the randomness. The reason the appearance of such randomness is compatible with determinism is most easily explained in an analogy I made in responding to Terrapin Station in my post here: imdb2.freeforums.net/post/549133/thread Your analogy seems backwards to me. The supposed collapse is more like a merging of paths, but your analogy involves forking. Regardless of that though, a quantum computer algorithm would derive an answer that is a statistical summation of the superpositions, so it should in theory always produce a predictable answer. I'll have to do more reading on this.More than merging, collapse interprets the other paths as disappearing when the "fork/measurements" happens. The other paths are what exist in a superpositioned state, though. If you assume that superpositioning is real, then the fork is what the wavefunction says happens. Two good intros to the basics of what I'm talking about: www.askamathematician.com/2010/10/q-copenhagen-or-many-worlds/www.preposterousuniverse.com/blog/2014/06/30/why-the-many-worlds-formulation-of-quantum-mechanics-is-probably-correct/
|
|
|
Post by general313 on Jun 18, 2017 23:35:59 GMT
Thanks for the links. Took a quick peek at the 2nd link, which reminds me that the current issue of Scientific American has the cover issue The Quantum Multiverse (tag line "A surprising connection between cosmology and quantum mechanics could unveil secrets of space and time"). Will check out the links (and the Scientific American article) more.
|
|
The Lost One
Junior Member
@lostkiera
Posts: 2,677
Likes: 1,303
|
Post by The Lost One on Jun 19, 2017 10:28:55 GMT
"The “denial” strategy says “The idea of... (an ontologically real wave function) is so profoundly upsetting to me that I will deny the existence of reality in order to escape having to think about it.” I don't really have a dog in this fight as I don't think it matters which model is most likely to be correct so long as they all make accurate predictions (which as far as I understand, they all do). But I thought this was interesting because I've actually seen those who favour indeterminism or at least a sort of agnosticism actually make a similar polemic against the determinists - that they are still too wedded to classical physics that they can't accept that maybe things aren't as neat as they'd like them to be. I don't really know enough about quantum physics to know if either polemic is more fair but maybe attacking people's motives behind their hypotheses should just be avoided?
|
|
|
Post by general313 on Jun 19, 2017 14:51:12 GMT
"The “denial” strategy says “The idea of... (an ontologically real wave function) is so profoundly upsetting to me that I will deny the existence of reality in order to escape having to think about it.” I don't really have a dog in this fight as I don't think it matters which model is most likely to be correct so long as they all make accurate predictions (which as far as I understand, they all do). But I thought this was interesting because I've actually seen those who favour indeterminism or at least a sort of agnosticism actually make a similar polemic against the determinists - that they are still too wedded to classical physics that they can't accept that maybe things aren't as neat as they'd like them to be. I don't really know enough about quantum physics to know if either polemic is more fair but maybe attacking people's motives behind their hypotheses should just be avoided? It reminds me of the Greek reaction to the discovery of irrational numbers. Supposedly they were so troubled by this realization that they tried to keep the discovery secret, which some observers think weakened Greek algebra.
|
|
The Lost One
Junior Member
@lostkiera
Posts: 2,677
Likes: 1,303
|
Post by The Lost One on Jun 19, 2017 17:13:09 GMT
I don't really have a dog in this fight as I don't think it matters which model is most likely to be correct so long as they all make accurate predictions (which as far as I understand, they all do). But I thought this was interesting because I've actually seen those who favour indeterminism or at least a sort of agnosticism actually make a similar polemic against the determinists - that they are still too wedded to classical physics that they can't accept that maybe things aren't as neat as they'd like them to be. I don't really know enough about quantum physics to know if either polemic is more fair but maybe attacking people's motives behind their hypotheses should just be avoided? It reminds me of the Greek reaction to the discovery of irrational numbers. Supposedly they were so troubled by this realization that they tried to keep the discovery secret, which some observers think weakened Greek algebra. I've always liked the Kuhnian view on these things - that people working within a paradigm find it near impossible to cast that paradigm off (as seen by resistance to irrational numbers, heliocentrism, quantum physics etc) This might be a case of two competing paradigms: determinism vs single universe. Perhaps if you're working within one, you will always see the other as ridiculous. Though I'm nowhere near knowledgeable enough about the details to say that with much certainty!
|
|
|
Post by Eva Yojimbo on Jun 19, 2017 23:05:17 GMT
"The “denial” strategy says “The idea of... (an ontologically real wave function) is so profoundly upsetting to me that I will deny the existence of reality in order to escape having to think about it.” I don't really have a dog in this fight as I don't think it matters which model is most likely to be correct so long as they all make accurate predictions (which as far as I understand, they all do). But I thought this was interesting because I've actually seen those who favour indeterminism or at least a sort of agnosticism actually make a similar polemic against the determinists - that they are still too wedded to classical physics that they can't accept that maybe things aren't as neat as they'd like them to be. I don't really know enough about quantum physics to know if either polemic is more fair but maybe attacking people's motives behind their hypotheses should just be avoided? They do all make the same (accurate) predictions, and not worrying about interpretations is the standard "shut up and calculate" approach promoted by most experimental physicists; still, there are those out there that, like Einstein did, want to know the truth even if the truth was pragmatically useless. I'm sure you can make the polemic go both ways (you can with most things), but I don't think determinists would be so "wedded to classical physics" if QM and GR were made compatible, or if somehow the former subsumed the latter, or something along those lines. As it is, you have these two theories that are among the most widely successfully tested in the history of mankind... and they're inexplicably incompatible with each other. Besides Occam favoring the simplicity of the deterministic interpretation (it's really the "neat" theory since it's not adding anything to fundamental formalism), the deterministic interpretation is at least compatible with GR in theory by also being local and real; though we still don't know how gravity works on the quantum level. As for avoiding polemic, I think that's generally a good policy; but Sean Carroll admitted he was being polemical there, and I think it was meant to be taken more humorously than seriously.
|
|
The Lost One
Junior Member
@lostkiera
Posts: 2,677
Likes: 1,303
|
Post by The Lost One on Jun 20, 2017 8:32:50 GMT
They do all make the same (accurate) predictions, and not worrying about interpretations is the standard "shut up and calculate" approach promoted by most experimental physicists; still, there are those out there that, like Einstein did, want to know the truth even if the truth was pragmatically useless. Sure, I think that's only natural but it seems we're a long way from having anything close to certainty about the truth. But which form of determinism? I was reading this article on the subject: www.benbest.com/science/quantum.htmlHere he rejects the many worlds theory as an extreme violation of Occam. Though as he says (and I'm inclined to agree) the use of Occam in these matters as to what is really simpler is largely a judgement call. Also I still have misgivings about Occam in that a simpler theoretical model of reality should not be preferred to ontological simplicity. For instance perhaps things being at heart random and unpredictable is in its way simple, a brute fact of reality that allows no further investigation. While from a theoretical point of view it complicates matters greatly, perhaps it could be argued to be simpler ontologically than say positing many worlds or hidden variables. Fair enough.
|
|