Talk:De Broglie–Bohm theory

message: From the article as of 15 Feb 2011:
However, while standard quantum mechanics is limited to discussing experiments with human observers, de Broglie–Bohm theory is a theory which governs the dynamics of a system without the intervention of outside observers (p. 117 in Bell[10]).
The statement that "standard quantum mechanics" requires a human observer is not accurate. Feynman states explicitly (but I have not found the reference, sorry) that a consciousness is not required for the measurement process, only the existence of some perhaps microscopic or distant effects left behind by an experiment, which might in principle be used to reconstruct in retrospect what happened. In other words, effecting a "measurement" means leaving behind a track of some kind, whether or not it can feasibly be interpreted to yield the desired information. In this, Feynman's point of view seems so sensible as to appear obvious. I am not aware of any challenge to it.
Dratman (talk) 23:53, 15 February 2011 (UTC)
thread_title:  Human role in standard quantum mechanics is misrepresented 

message: The article confidently states that dBB agrees with standard QM, but this article states that it has
failed an experimental test. 1Z (talk)
So it does, but the claim is well-known to be utterly spurious, as was demonstrated in at least the following three references: 
"Two particle interference in standard and Bohmian quantum mechanics", E. Guay and L. Marchildon, 
J. Phys. A: Math. Gen 36, 5617 (2003).
"Comment on 'Bohmian prediction about a two double-slit experiment and its disagreement with standard quantum mechanics'", W. Struyve, W. de Baere, J. de Neve, and S. de Weirdt,J. Phys. A: Math. Gen. 36, 1525 (2003)
"Comment on 'Experimental realization of a first test of de Broglie-Bohm theory'", O. Akhavan, M. Golshani, J. Phys. B 37, 3777 (2004).
Zicovich (talk) 15:08, 7 March 2011 (UTC)
thread_title: Test

message: This sentence puzzles me:
"Because the known laws of physics are all local, and because non-local interactions combined with relativity lead to causal paradoxes, many physicists find this unacceptable."
All the known laws, except QM... Am I missing something? I just wanted to get feedback before changing it. Paxfeline (talk) 21:41, 21 May 2012 (UTC)
replies: text: Indeed your criticism concerns this edit of 30 Jan 2012 that did not improve the article - to be reverted or at least re-worded. --Chris Howard (talk) 19:37, 8 July 2012 (UTC)
thread_title:  Nonlocality 

message: I may be wrong, but there might be an error in this section.  The text currently reads: "Bell showed that von Neumann's objection amounted to showing that hidden variables theories are nonlocal, and that nonlocality is a feature of all quantum mechanical systems" (emphasis mine).  However, my interpretation of the preceding material is that it should actually read: "... showing that hidden variables theories are local ..." (emphasis mine).  Otherwise it reads as if von Neumann was objecting to hidden variable theories because they shared nonlocality with actual quantum mechanical systems.  Which wouldn't really be an objection at all.  Perhaps I'm missing something subtle here?  Anyway, I'll change it if I don't hear anything to the contrary.  Cheers, --PLUMBAGO 14:15, 25 February 2013 (UTC)
replies: text: The hidden variables theories that the Bell Test disproves are those that are local, that is, more or less classical in nature, but with unknown or "hidden" effects added. These were the theories that Einstein hoped would be correct, since he didn't like wave function collapse, probability as axiomatic, and other mysterious aspects of Bohr's theory. But the pilot wave theory that David Bohm proposed in 1952 converted de Broglie's local theory into a nonlocal theory, one that still reproduced the probabilistic effects of the Copenhagen Interpretation. All of the strange nature of QM was now located just in the guiding equation (part of the Schrödinger wave function), which Bohm viewed as a nonlocal quantum force that would guide particles in a wavelike way, taking the entire experimental configuration (both slits) into account. Then the subsequent trajectories of particles in the two-slit experiment were the results of interaction with that force, in a classical way. So, yes, there was an experimental objection, and yes, John Bell liked the way Bohmian mechanics used a nonlocal force to resolve the local hidden variables error. David Spector (talk) 13:02, 30 July 2020 (UTC)
thread_title:  Bell and De Broglie–Bohm theory 

message: I tried to apply a Bohmian equation to a hydrogen atom. I got that an electron falls into the nucleus along a helical path at a constant speed. After that I took into account uniformly increasing magnetic field, with decreasing radius of the electron trajectory. In this case, an electric field arises, which is directed against of the decreasing of the radius of the trajectory. In this case, there are no electromagnetic waves, so there is no loss by radiation. Thus, we have a stationary orbit for the ground state of the hydrogen atom. 
The same way you can consider the deuterium nucleus, using the Yukawa potential and taking into account relativistic corrections, and thus, learn more about the nature of intranuclear spin interactions.
Mark L. Gurari  — Preceding unsigned comment added by 76.10.139.212 (talk) 03:21, 2 March 2013 (UTC)
replies: text: An interesting theory. Unfortunately, there is no place in Wikipedia for original research. This must be discussed in other fora, such as Stack Exchange/Physics or arXiv. David Spector (talk) 13:07, 30 July 2020 (UTC)

text: Indeed, the failure of the hydrogen atom to spontaneously collapse was one of the first clues that nature works in a quantized way in the very tiny regime. Observation failed to confirm the naive theory that atoms were like our solar system, with electrostatic attraction substituted for gravity. David Spector (talk) 01:54, 25 November 2021 (UTC)
thread_title:  A hydrogen atom ground state in Bohmian mechanics 

message: I removed the link between the term "foliation of space-time" and the article "frame of reference".  Foliation is used several times here in reference to Relativity, but remains totally unexplained and undefined in either article.  The term does not appear at all in the Frame of Reference article.  Using that as a reference is really poor authoring/editing.  I expect that the two concepts are heavily related, but unless someone wants to EXPLAIN the relationship, it is simply obfuscation to add a link that explains nothing.  It is just as poor a practice to use a term with virtually no explanation.  Can someone FIX this absurdity?173.189.78.18 (talk) 16:44, 15 July 2013 (UTC)
thread_title:  Foliation 

message: I think this article http://newsoffice.mit.edu/2014/fluid-systems-quantum-mechanics-0912 also has some relevance to the topic and might add value to the discussion. I cannot incorporate it into the main article due to the lack of expertise. It is also refrenced here: http://www.sciencedaily.com/releases/2014/09/140912120634.htm.  —  comment added by EricBright (talk • contribs) 18:51, 14 September 2014 (UTC)
replies: text: Yes, the bouncing droplet experiments can replicate some aspects of QM (double-slit). But, so far, it is not clear whether the nonlocal effects shown by these experiments use the same mechanism as nature does in the very tiny regime. For now, it is simply a very convenient (though delicate) model, one that is currently being explored. David Spector (talk) 02:00, 25 November 2021 (UTC)
thread_title:  Bouncing droplet experiments 

message: An early paragraph in this article mentions two polls that are meant to show that the de Broglie-Bohm theory is taken seriously by physicists, and has footnote 2 and 3 attached. If you follow the footnotes, the first "poll" involved 8 physics students in a hut in the forest. This sample size is far too small to be meaningful. Furthermore, physics students are hardly experts on the subject. The second "poll" had only 33 respondents and the paper specifically stated that the poll the purpose of the poll was "not so much of finding a “truly representative sample”. — Preceding unsigned comment added by 129.63.129.196 (talk) 16:58, 29 October 2014 (UTC)
thread_title:  Referenced Polls are useless 

message: "The main fact to notice is that this velocity field depends on the actual positions of all of the N particles in the universe"
1) Is the theory readily generalisable when dealing with an Infinite universe (some people would clearly ask what an 'infinite universe' would actually entail). 
 
2) The Velocity field equation in this case does NOT indicate HOW all the particles in the universe affect the velocity field, only that they do,   according to the diff eqn.  that is, the wavefunction is arbitrary.  
ASavantDude (talk) 15:43, 12 September 2016 (UTC)
thread_title: Infinite or Finite Universe?

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thread_title:  External links modified 

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thread_title:  External links modified 

message: The Hartle–Hawking state page indicates that "the Hartle–Hawking state universe has no beginning...it simply has no initial boundaries in time nor space."
The De Broglie–Bohm theory page states that "the latter depends on the boundary conditions of the system".  
Do these two observations, put together, imply that there is no non-local hidden variables theory that is compatible with the idea of the Hartle-Hawking state? (presumably the Hidden variables theory needs boundary conditions given that it is deterministic - but the Hartle-Hawking state article seems to negate this possibility).  
ASavantDude (talk) 20:29, 23 September 2017 (UTC)
replies: text: A very clever question. While Schrödinger's equation is frequently accompanied by claims of its application to the entire universe, what is actually meant is that the environment of a QM experiment must be considered as being a conceptual and very real part of the experiment. This is clearly shown in the two-slit experiment when a measurement is added to reveal which slit a particle went through. The measurement itself has high enough energy and interaction to perturb the paths of the particles enough to destroy the interference pattern due to the two slits. The measurement may be considered a part of the universe "outside of" the two slits, but in this case must be considered as part of the configuration of the experiment itself. However, a subway train moving 300 meters away from the experiment is observed to have a negligible effect (in this experiment). So, while any event in the entire Universe may be said to "have an effect" everywhere else, that effect for most forces falls off at least with the square of the distance, and can certainly reach zero. However, I'm not sure this question itself is relevant to this article, which may account for its getting no response in 2 years. David Spector (talk) 16:20, 29 July 2020 (UTC)
thread_title: "the latter depends on the boundary conditions of the system"

message: The article states : 
-\frac{\partial\rho}{\partial t} = \nabla \cdot (\rho v^\psi) 
But the idea of  v^\psi  seems like a typo to me.  Did the contributor of this forumula intend the following instead?:
-\frac{\partial\rho}{\partial t} = \nabla \cdot (\rho v\psi) 
Any response appreciated.  
ASavantDude (talk) 20:01, 21 March 2018 (UTC)
thread_title: Possible Equation Typo

message: The section "Bohmian mechanics" is woefully inadequate.
For example, it fails to mention the very heart of Bohmian mechanics, that particle trajectories can be made deterministic simply by adding the intial velocities of the particles to the wave function. While the wave function describes with precision all the effects of an experimental geometry, it leaves much mystery under the Standard, or Copenhagen Interpretation of quantum mechanics. You cannot trace a particle trajectory even if you know the force field acting on it without the initial position of that particle.
Bohmian mechanics is not based on Born's Rule, as stated in this section, but derives it from first principles, analogous to the Maxwell-Boltzmann derivation of black body temperature.
Bohmian mechanics has been verified by several experiments, in which the trajectories of particles through one slit of the double-slit experiment have been experimentally determined. They agree with the predictions of Bohmian mechanics. The randomness comes from the variation in location of the particles as they enter the slit, and the "wave interference" distribution comes from the Bohmian force field determined by the Schrödinger equation. There is a widely-published computer generated image of this force field, and it is very interesting to see clearly how it determines the screen pattern.
We may be irritated by the apparent influence of Slit 1 when a photon passes through Slit 2, but this nonlocality is truly the way QM works, and reaches its peak of strangeness with QM entanglement, in which separate particles share a common QM state.
Our commonsense view of physics was determined by our senses, which operate in the standard size regime. But physics is not limited to the standard regime. For example, we want to understand how Nature works in fundamental particles, which behave strangely in the tiny regime.
The Standard Interpretation of QM was pushed on physics by Neils Bohr and has survived intact in spite of its basis being a set of axioms that must not be questioned or investigated. It enshrines wave/particle duality, wave function collapse, and many other aspects of QM as strange principles that must be accepted instead of investigated. David Bohm was free of such restrictions, and his 1952 theory has held up well in spite of the hand-waving prejudice against it. John Bell, who famously disproved all local "hidden variables" theories, wrote near the end of his life that Bohm's nonlocal "hidden variables" theory passed his test. David Spector (talk) 11:29, 30 June 2021 (UTC)
thread_title:  Inadequacy of "Bohmian mechanics" 

message: It seems to me that these pages need to be either merged or distinguished:
https://en.m.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory
https://en.m.wikipedia.org/wiki/Pilot_wave_theory
There is a lot of different information in each, but they seem to be the same topic. Etomology (talk) 18:27, 24 November 2021 (UTC)
replies: text: Thank you for the comparison. Too bad there isn't a clear winner, but I think the choice of main title isn't too important, as WP redirects would provide appropriate search targets and since the most common/popular name for this theory/interpretation is likely to change with time, as physicists start taking it more seriously. David Spector (talk) 21:36, 2 December 2021 (UTC)
thread_title:  Merger 

message: The two articles both seem to discuss exactly the same topic: the interpretation of quantum mechanics and theory behind quantum mechanics first proposed by David Bohm in his two-part paper in 1952.
I would urge that these two articles be merged, using appropriate WP synonyms (redirects) for search purposes. I recognize that merging these articles may be a major project, one which I may not be able to find the time to undertake.
I would further urge that a distinction be drawn between the local hidden-variables theory of de Broglie and the later nonlocal hidden-variables theory of Bohm. In brief, Bell proved that de Broglie's theory (initially favored by Einstein) was incorrect and that Bohm's theory was correct.
To this day the confusion caused by lumping together the incorrect early pilot-wave theory with the later correct pilot-wave theory has been one of several obstacles to the widespread acceptance of Bohm's theory.
Another obstacle to acceptance was Bohm's getting in trouble with the House Committee on Un-American Activities, which, under the leadership of Sen. J. McCarthy hunted Communists as being the primary evil of our times. Appearing before the Committee was in many cases enough to brand a person as a Communist, regardless of actual membership in the party.
And another obstacle was Bohm's long-time interest in the philosophy of nonduality in general and of J. Krishnamurti in particular. But note that Erwin Schrödinger himself agreed with nonduality enough to write a book that was mostly about it.Erwin Schrödinger, "What is Life?", 1944, What is Life website
I would like to see some additions to the merged article: an explicit discussion showing how Bohm eliminates the need for the axioms required by the Copenhagen Interpretation, and examples showing how the Bohm theory removes nondeterminism from at least the three following experiments: double-slit, light-polarizing filters, and the silver atom or electron spin effects of sequentially-connected Stern-Gerlach interferometers. David Spector (talk) 20:37, 24 November 2021 (UTC)
replies: text: Thank you for the comparison. Too bad there isn't a clear winner, but I think the choice of main title isn't too important, as WP redirects would provide appropriate search targets and since the most common/popular name for this theory/interpretation is likely to change with time, as physicists start taking it more seriously. David Spector (talk) 21:36, 2 December 2021 (UTC)
thread_title:  Agree with Merging 

message: It seems the current article's organization doesn't follow the traditional style of putting the history as one of the first topics (it's currently at the bottom). I suggest this to be changed to fit what seems to be the more traditional organization of Wikipedia articles.
Momergil (talk) 03:22, 16 September 2022 (UTC)
thread_title:  History 

message: I think it would immensely improve the article to give a brief explanation of how the theory explains the double slit experiment. 192.38.90.165 (talk) 08:28, 23 November 2023 (UTC)
thread_title:  Double slit experiment? 

message: I started to make one small change, but as I read more I realized the article has numerous problems. Thus I have by now made a number of changes.  The most visible ones concern tightening the intro. It should be a succinct summary but it had grown with some long blocks of quotes etc. I moved the quotes to the History section.
The other changes are mostly around incorrect or misleading content. I tried to squeeze my justification in to the edit summary but I will reply to any complaint about my changes made here in the Talk pages.  I want to be clear I'm not a Bohm-hater (or supporter), I just want the article to be clear and correct. Johnjbarton (talk) 17:02, 18 March 2024 (UTC)
thread_title:  Recent changes I made. 

message: The (tiny) experimental section has a cryptic comment about ESSW. There is actually quite a lot of work related to this paper. 
* Frumkin, Valeri, and John WM Bush. "Misinference of interaction-free measurement from a classical system." Physical Review A 108.6 (2023): L060201.
* Frumkin, Valeri, et al. "Real surreal trajectories in pilot-wave hydrodynamics." Physical Review A 106.1 (2022): L010203.
* https://thales.mit.edu/bush/wp-content/uploads/2015/01/Bush-AnnRev2015.pdf
In particular some of the work out of JWM Bush's group shows that the surreal trajectories of ESSW are real trajectories in classical hydrodynamics. Johnjbarton (talk) 19:09, 18 March 2024 (UTC)
thread_title:  ESSW, surreal trajectories, many hydrodynamic results.