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Comment by jostylr | Hacker News Reader

I never understand why the double slit experiment puzzles people. Is it not clear that we are dealing with particles guided by a wave? This is Bohm's theory and it works perfectly well for answering these questions.

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Bohm theory is not well regarded by most of physicists, as it is a desperate try to use some intuitions from classic word. It helps with understanding double slit the same way as "God created it" helps with understanding universe - makes one calm and content. You may argue that Bohm theory works... but well, once you get other systems, you run into nasty complications and loose symmetries.

I believe the Born Rule[1] may address some of these concerns.

[1] http://en.wikipedia.org/wiki/Born_rule

You can reject Bohmians as being emotionally attached to their ideas, but you can also reject non-Bohmians for the same reason. Many (most?) who grasp quantum mechanics on any level feel they've climbed an important intellectual mountain and don't want to find out they discarded their intuition for no good reason.

Emotional attachment it one thing. But pilot wave stuff does not explain anything, adds complexity and makes problem for more complicated systems that "a single particle in spatial representation". I do know professional physicist who prefer Bohmian interpretation (but most I know are in some version of Many Worlds or Quantum Bayesianism). The thing is whether a choice is made for purity or because of adherence to classical physics.

BTW: If you want to get some data:

http://www.preposterousuniverse.com/blog/2013/01/17/the-most...

I'm well aware of the adoption rates of Bohmian Mechanics. What I object to is dismissing it as being the product of emotions and not differing ideas about the universe. On that graph 42% went to the Copenhagen Interpretation whose fans are just as emotional as Bohm's.

Feel free to reject BM on technical merit, really, I couldn't care less.

As an aside, the graph is a little funky since Bohmian Mechanics is not an interpretation of QM but a reformulation of it.

I would guess that for Copenhagen interpretation its mostly experimentalists. While its coarse grained (i.e. is problematic at timescales of the "measurement") it does not add extra stuff.

Plus, let us take a very simple system: one particle in a two-level system. Does Bohmian make it simpler for you?

> Bohmian Mechanics is not an interpretation of QM but a reformulation of it.

Could you explain the difference?

Different "interpretations" of QM are in a large part just philosophy at this point. Individual physicists might find one interpretation more appealing, but it doesn't actually have much, if any, impact on their work.

A reformulation of a physical theory is a new mathematical approach. It might be motivated by a particular interpretation, but since existing approaches are all confirmed by experiment, it won't actually offer different predictions.

However, it might be substantially easier to calculate a particular quantity in one formulation. Or, it might naturally imply a way to extend QM that will ultimately produce different predictions than the original formulations. (At some scale that we haven't yet probed.)

Feynman's path integral formulation[1] is a pretty notable example of this. I've never looked at the Bohmian thingy, but the fact that I've heard more about it on reddit/HN than from physicists is not an encouraging sign...

1. http://en.wikipedia.org/wiki/Path_integral_formulation

We're well above my pay grade here but this is how I look at it.

A different system of mechanics is a different system of math, basically. One system of mechanics can have many interpretations but those interpretations may not be experimentally different from each other because they fundamentally calculate things in the same way. Bohmian Mechanics (correct me if I'm wrong) isn't just a different window-dressing on QM, it's built differently, that's why it can't make all the predictions of QM.

At the end of the day I don't really have a side in all of this, but I think Bohmian mechanics is at least interesting for what it is.

Hardly desperate. One can easily derive Bohm's equation even before Schrodinger's equation just by using de Broglie's relation. It is not about intuitions form the classical world, but rather noting that we have particulate events. Always. Heck, in cloud chambers, we see paths (or so they tell me -- I am not an experimentalist).

When creating a theory, it helps to start with the stuff whose behavior will explain your results. Who would start with a wave function on configuration space of the universe when you do not even have any configurations of stuff? The whole thing seems farcical.

I am unaware of any nasty complications. Spin, many particles, creation and annihilation of particles, scattering experiments, and all the rest are not only easily dealt with in Bohm's theory, but actually explain what is going on.

It's not remotely clear, because although this concept explains the result it does not uniquely explain it, and it does not make predictions that allow it to be distinguished from many of the other potential explanations.

The double slit experiments puzzle people because they wonder how the thing works. A particle guided by a wave doesn't help much - a wave in what? How does that physically guide the particle? What would happen to the waves after the particle has hit the screen - do they slosh about or head across the universe or what? Why do they only effect that particle? etc.

The wave of one particle is just a suitable approximation. The wave is a wave in configuration space, one for the whole universe. This is also what it is in standard quantum mechanics or in many worlds. It is always the same wave. Somehow Bohmian mechanics gets a bad wrap because it takes the wave seriously despite the other interpretations only having a wave function in their views.

The fact that quantum mechanics limits the information density of a field is a feature not a bug. Giving absolute numbers of position and momentum makes physicists pretty uncomfortable.

I think it's the argument for the hidden variable 'issue', mostly. It may be 'clear' but it's also philosophical at the same time.

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