Isn't this supposed to be a debate forum?

  • Thread starter jonjacson
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I asked about alternative formulations of quantum mechanics not using the Hilbert space and I got a mixture personal attacks and a blocked thread.

Is this normal?

I created this thread and got blocked:

https://www.physicsforums.com/threa...-hilbert-space-for-quantum-mechanics.1003389/

According to all the people who answered in that thread the Hilbert space is the only way to compute in quantum mechanics. It is like this Hilbert space is a religion.

Come on guys, I am sure you all know in Classical Mechanics you have Newton laws using forces and accelerations but you also have alternative formulations like the Euler Lagrange equations, or the Hamilton formulation.

Just in case you didn't know I copy and paste:

Hamiltonian mechanics is a mathematically sophisticated formulation of classical mechanics. Historically, it contributed to the formulation of statistical mechanics and quantum mechanics. Hamiltonian mechanics was first formulated by William Rowan Hamilton in 1833, starting from Lagrangian mechanics, a previous reformulation of classical mechanics introduced by Joseph Louis Lagrange in 1788. Like Lagrangian mechanics, Hamiltonian mechanics is equivalent to Newton's laws of motion in the framework of classical mechanics.

So it is possible to have several mathematical formulations of the very same discipline, that means my question was more than appropiate, or in other words, blocking that thread was innapropiate from my point of view.

Continue attacking people that makes proper questions and probably you will end up here alone.
 
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Answers and Replies

  • #2
mcastillo356
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Don't get angry, please. I not know the context. I'm just trying to calm you down.:smile:
 
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  • #3
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I was curious had you posted again. In my post on the thread I listed three other formalisms if you are interested. I think from the phrasing of your OP to others it sounded like you were trying to propose a new formalism.
 
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  • #4
f95toli
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No, it is not primarily a debate forum.
The forums main goal is to teach people "established" physics, i.e. results available in textbooks or in articles published in scientific journals.
Sometimes there is of course disagreement when in comes to how to understand these results which can result in (long) discussions. However, I suspect this is not what you mean by "debate".

This forum is not a good place to discuss personal theories and/or ideas which can not be supported by results from the literature.
 
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  • #5
Ibix
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To answer the question in your thread title: it is a discussion forum, not an unrestricted debate forum.

I'd say that what happened in that thread is that you defined the conversation as "a game" where "Hilbert space...[is] not allowed". Unfortunately that runs smack into a wall: any alternate formulation of QM is a Hilbert space in disguise, so disallowed by your formulation of the question, and any theory that is not equivalent to a Hilbert space is a non-mainstream theory, so disallowed by forum rules (unless you can provide a specific valid reference, which you didn't do). That will be why you got the responses you did and why the thread was closed.

What did you want to ask about with your thread? If you wanted to know about alternate formulations of QM, Kolmo listed a few. You could do some research and/or start a new thread asking for some references or asking specific questions about them. If you wanted to discuss alternative theories you would need to provide a valid reference. If you wanted to do alternate theory development then this isn't the place.
 
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  • #6
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I was curious had you posted again. In my post on the thread I listed three other formalisms if you are interested. I think from the phrasing of your OP to others it sounded like you were trying to propose a new formalism.

Yeah I was looking for that. Thank you very much.

No, I didn't propose anything, just wanted to know solid, well accepted and respected official formalisms.
 
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Yeah I was looking for that. Thank you very much.

No, I didn't propose anything, just wanted to know solid, well accepted and respected official formalisms.
Note they are listed in order of decreasing use across subfields. By far the most important one to learn is the Path Integral formulation. The second is only used in more mathematical treatments of physics and the third is only used in some areas of quantum information.
 
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  • #8
atyy
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Note they are listed in order of decreasing use across subfields. By far the most important one to learn is the Path Integral formulation. The second is only used in more mathematical treatments of physics and the third is only used in some areas of quantum information.
But as you said on the other thread, those are equivalent to the Hilbert space formalism, so the Hilbert space formalism cannot be disallowed.
 
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  • #9
atyy
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Like Lagrangian mechanics, Hamiltonian mechanics is equivalent to Newton's laws of motion in the framework of classical mechanics.
That's why your question was nonsensical. If formalisms are equivalent, you cannot say that one of them is disallowed if their equivalent formalisms are allowed.
 
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  • #10
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I think "disallowed" was just an unfortunate phrasing of "if you were not using it". The OP was really just asking "what are the other formalisms" in a confused way.
 
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  • #11
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I think the title of your thread "Do we really need the Hilbert space for QM?" was a reasonable question and this was the question I chose to answer in my response. Indeed I think you were advised of a number of other approaches to QM that may be the answer you were looking for. I'm not entirely convinced that my own suggestion of the geometric algebra approach could be described as a Hilbert space in disguise but perhaps that is a subject for another thread.

I would agree that the rest of your initial post, ("lets play this game", "disallowed") perhaps unintentionally muddied the waters of the question you were quite reasonably trying to ask.
 
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  • #12
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personal attacks

attacking people

Um, where? I see 0 (zero) attacks. But, yes, I do agree that purpose of your thread was a little bit misunderstood.
 
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  • #13
DaveE
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I think part of the problem was that your question was nearly impossible to answer. Similar to asking "What if there was another universe with different physical laws, what would it be like?" The answer could be anything. It may have been more appropriate in the Science Fiction Forum. I'm sure that's not what you intended, but that's how it appears to a bunch of physicists.
 
  • #14
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@Justice Hunter I presume that this complaint was partially motivated by the closing of this thread?

Relativity is one of the most fascinating and elegant ideas that humanity has ever come up with, and just about everyone who has put in the effort required to understand and appreciate it is glad that they did. It's up to you whether you want to try it for yourself.... but if you do, a necessary first step is listening when people who have already been there tell you that you're on the wrong track.
 
  • #15
Ibix
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you can describe physics without math, let alone the actually math that's currently used.
You can describe physics (edit: kind of, anyway) without maths, but you can't do physics without maths.
geodesics [...] are just lines connecting points together on a geometry
Even interpreting "on a geometry" as meaning "on a manifold", that description misses out an awful lot. The correct definition is that a geodesic is a path that parallel transports its own tangent vector.
you can literally make any language to describe any mathematical abstraction.
Sure. Now see if you can write ##G^{\mu\nu}=\frac{8\pi G}{c^4}T^{\mu\nu}## in English (or other natural language of your choice) in the twelve characters it took me to write it in maths. For extra credit, use your natural language version to make quantitative predictions of something. When you've done that, then you can say that you don't need maths to do science and expect me to keep a straight face.
the typical response from the ego-strokers is that your question was "stupid" or that "it doesn't make sense."
jonjacson's question was just badly phrased, I think. Yours this afternoon was based on a quotation that was nothing more than a catastrophic misunderstanding of relativity, and you wouldn't listen when we kept pointing out that the whole basis of the thread was nonsense. You aren't obliged to listen to us, of course, but it makes me wonder what purpose you thought asking questions would serve if you were only going to listen to answers that didn't point out the problems with what you asked.
 
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  • #16
Vanadium 50
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Well, Mr. Hunter, we have on the one hand one group of people who have studied a subject, in some cases for years. On the other we have someone who has not even studied the subject but thinks the first group is wrong.

Who has the problem with ego?
 
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Anyway...so the typical response from the ego-strokers is that your question was "stupid" or that "it doesn't make sense."
This is only an abbreviation. But you are right. Maybe we should take the time and respond in the extended version:

"Your question reveals that an appropriate answer would require holding several lectures in several fields, beginning on a very elementary level. Unfortunately, this isn't something we could provide, despite our continuous efforts to teach and help students."

We can talk about a theory of everything, but we cannot do it with more than a handful of people and in a language, all others won't understand. Any other form would only be small talk and very likely nonsense.
 
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  • #18
PeterDonis
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it is possible to have several mathematical formulations of the very same discipline
Yes, it is possible. But "possible" is not the same as "guaranteed". Nor is it the same as "known".

We know multiple formulations of Newtonian mechanics are possible because we know the formulations. Nobody knows a formulation of QM that doesn't involve Hilbert spaces. So asking what such a formulation would be like is pointless, since we don't have one to go look at. As I said in the thread, if you don't like that, then go invent a non-Hilbert space formulation of QM, the way Hamilton invented his different formulation of Newtonian mechanics.
 
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  • #19
PeterDonis
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They are allowed to insult you personally
If you think someone else pointing out where you are wrong, or where what you are saying doesn't make sense, is an insult, you need to adjust your attitude. We are not responding to you personally. We are responding to the statements you make in your posts, which are about physics, not about you.
 
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  • #20
PeterDonis
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I'm not entirely convinced that my own suggestion of the geometric algebra approach could be described as a Hilbert space in disguise
Geometric algebra is not just a different formulation of quantum mechanics; it's a different formulation of all of physics (or at least it claims to be). So it's not really comparable to the different formulations of QM alone, or QM/QFT. It's more comparable to, say, spin foams or loop quantum gravity, which are attempts to encompass all of physics, not just QM.
 
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  • #21
You can describe physics (edit: kind of, anyway) without maths, but you can't do physics without maths.

And the OP's question wasn't whether you can do physics without math...it's whether there is a formalism that exists that doesn't use Hilbert Space.

Like I said in my response, you can describe QM with any language...and what's variable is the approximation of that description. You can describe QM by saying "It's particles acting like waves bro" and you can make predictions based on that information...how accurate those predictions are is going to be based on how well the description is formalized. Math is no different, and approximates QM to the best of current human knowledge...doesn't mean a BETTER or even DIFFERENT formalism doesn't exist out there.

Great example, Fine Tuning and Renormalization. Do you really think this is gonna fly forever? Of course not, someone is gonna come along, with some other model that better describes nature so that you don't have to put "off by 120 orders of magnitude" in fine print on your observables.
 
  • #22
PeterDonis
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the OP's question wasn't whether you can do physics without math
Which is irrelevant since the one who made that claim and is getting pushback about it is you, not the OP of this thread.

You can describe QM by saying "It's particles acting like waves bro" and you can make predictions based on that information...how accurate those predictions are is going to be based on how well the description is formalized.
Um, "formalized" means "math". "Particles acting like waves bro" doesn't predict anything.
 
  • #23
"Particles acting like waves bro" doesn't predict anything.

Okay you tell me "Particles act like waves bro"

I can say Prediction: "Okay bro then sticking a particle through a double slit will produce an interference pattern, just like other waves."

So yea, you can predict things in languages that aren't math...how accurate is the prediction is based on the level to which it's formalized. QM predictions are accurate to with 10^12 decimal places, not so much using English but that all depends on how well you describe it. You describe it well enough, you can get more and more accurate predictions.

That's what...thought experiments are for...such a novel idea right?
 
  • #24
PeterDonis
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I can say Prediction: "Okay bro then sticking a particle through a double slit will produce an interference pattern, just like other waves."
But a particle going through a double slit does not produce an interference pattern. It produces a single dot on the detector screen. So your prediction is wrong.
 
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  • #25
Nugatory
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You can describe QM by saying "It's particles acting like waves bro"
Yes, if we're talking to our little bro and want to mislead him. But the only people who would consider that a description of QM are people who have no idea what QM is. To be fair, they'd be in good company - there are a lot of bad popularizations out there.

Quantum mechanics does not (as least for me - tastes vary) have the same compelling beauty and elegance as relativity. Nonetheless, my comment above ("just about everyone who has put in the effort required to understand and appreciate it is glad that they did. It's up to you whether you want to try it for yourself.... but if you do, a necessary first step is listening when people who have already been there tell you that you're on the wrong track.") applies to quantum mechanics as well. If you're starting with the idea that it's particles acting like waves, you're taking a wrong turn that many physicists took at the begining of the last century, but recognized and abandoned a few decades later. What do you have to lose by listening to people who have already been through it?
 

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