Smolin's Edge Response - Deterministic Quantum Theory?

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Main Question or Discussion Point

Did anyone read Lee Smolin's response to the Edge.org question: "What are you worried about?"

http://edge.org/response-detail/23778

Opening paragraph:

I worry that we don't really understand quantum phenomena. We have a successful theory—quantum mechanics, which has passed every experimental test since it was formulated in 1926 and which is the foundation for our understanding of all of physics—except gravity. It is the basis of new technologies of quantum information and computation which are presently under intensive development. Still, I don't believe quantum mechanics gives a complete description of nature. I strongly believe there is another, truer description, waiting to be discovered.
 

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  • #2
marcus
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As I recall he didn't say anything very definite about what such a theory might look like, so I didn't pay very close attention. It's not unusual for people to propose deterministic theories that they think might underlie and give rise to the quantum probabilistic behavior we observe.

Last year I heard Gerard 't Hooft give two talks about his current pet idea for a deterministic quantum theory---one was a well-attended seminar with a high proportion of faculty and postdocs. So there is interest in this kind of thing. Personally it didn't grab me, but 't Hooft is congenial and impressive to watch.

About 5 years ago, Smolin was proposing such a thing---I think it may have been based on what he called "disordered locality" but I could be confusing two research papers. I don't have an accurate memory of it. Anyway he too, at that time, had a definite proposal for a deterministic basis for quantum theory.

There may be conferences which have been all or part devoted to this kind of thing. For some reason I don't find it at all interesting. Anyway I think Smolin and 't Hooft are just two examples out of many who've aired thoughts about it.
 
  • #3
member 11137
As I recall he didn't say anything very definite about what such a theory might look like, so I didn't pay very close attention. It's not unusual for people to propose deterministic theories that they think might underlie and give rise to the quantum probabilistic behavior we observe.

Last year I heard Gerard 't Hooft give two talks about his current pet idea for a deterministic quantum theory---one was a well-attended seminar with a high proportion of faculty and postdocs. So there is interest in this kind of thing. Personally it didn't grab me, but 't Hooft is congenial and impressive to watch.

About 5 years ago, Smolin was proposing such a thing---I think it may have been based on what he called "disordered locality" but I could be confusing two research papers. I don't have an accurate memory of it. Anyway he too, at that time, had a definite proposal for a deterministic basis for quantum theory.

There may be conferences which have been all or part devoted to this kind of thing. For some reason I don't find it at all interesting. Anyway I think Smolin and 't Hooft are just two examples out of many who've aired thoughts about it.
As every one knows here, I like to play the role of "mister naive" and concerning that topic (a deterministic origin for the quantum theory), I have a old standing question. When I was a student (thirty years ago), teachers used to say that electrons are situated/moving "around" the nucleus of a given atom and that we may only find them at a given place with a given probability. That probability is normalized in such a way that, if we integrate it on the whole spacetime, we find 1. This is the more or less official quantum interpretation; the theory has introduced the probability of presence as an indirect consequence of the HUP. Well this is one side of the story. In between I have heard about the tunnel effect (also another consequence of the way of thinking developped by the quantum theory). So, now comes my questions: "Do we actually consider that a particle which is tunneling (in extenso: traveling in an energetically forbidded region - things being seen from the classical point of view) exists in the classical sense of that word?" If the answer is: no (= a tunneling particle does not exist in our classical world), could we not see here the starting point for an alternative and deterministic interpretation? In extenso, if have only 50 chances under 100 measurements to find an electron here and now, does not this fact only means that that electron is just tunneling the half of the time here (due to some topological modifications)? Despite of my not optimal english I hope my question is clear enougth. Do you have some scientific references going in that direction? Thanks
 
  • #4
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So, now comes my questions: "Do we actually consider that a particle which is tunneling ..... exists in the classical sense of that word?"
No, I don't think so; but nevertheless it seems a 'real' phenomenon ....quantum stuff does 'exist' in our world.

how about tunnel diodes, Josephson junction, a possible way the big bang started, Hawking black hole radiation, fission, fusion.......

are my first thoughts.....


ok, so as not to appear too idiotic, I checked...

"quantum tunneling" turned up similar stuff..

http://en.wikipedia.org/wiki/Quantum_tunneling

See what you think....

also,bunch of references given at the end of the article.
 
  • #5
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Did anyone read Lee Smolin's response..........

I have seen that quote.....and I have a book of Smolin's that treks along those lines:

Smolin
Still, I don't believe quantum mechanics gives a complete description of nature. I strongly believe there is another, truer description, waiting to be discovered.
THREE ROADS TO QUANTUM GRAVITY, 2001, a book for the general public...

It's a story of how different theories relate to at an as yet incomplete quest for a theory of quantum gravity ..things like GR, QM, LQG, holographic insights, string theory,etc.....I found it a good introduction to some of the things we think we know and some we know we don't know.
 
  • #6
I am happy to read the Smolin words. When we start out as young students, the quantum is very mystify. Then we learn what the maths are and there is a bifurcation. Some will say, "Now I understand." Others will say, "I still do not understand." To me quantum theories are engineers solution to philosopher's problem. So the students who get diploma and say "Now I understand," those are the engineers. The physicist agree with Smolin and do not understand.

"If you are hammer, all problems look like nails." ...so it is with people who "understand" quantum theories.
 
  • #7
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John Archibald Wheeler: Law Without Law, 1983
http://what-buddha-said.net/library/pdfs/wheeler_law_without_law.pdf

“Is thre not some underground machinery beneath the working of the world which one can ferret out to secure an advance indication of the outcome? Some secret determiner, some “hidden variable”? Every attempt, theoretical or observational, to defend such a hypothesis has been struck down. Not the slightest hard evidence has ever been found that would throw doupt on the plain, straightforward prediction of quantum mechanics, the prediction that no prediction is possible. Probability? Yes. A definite forecast? No. Einstein could be unhappy that “God plays dice”; but Bohr could tell him jokingly, “Einstein, stop telling God what to do.”
 
  • #8
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Carlo Rovelli has this to say about quantum phenomena in UNFINISHED REVOLUTION [a research paper]

At the beginning of the XX century, General Relativity (GR) and Quantum Mechanics (QM) once again began reshaping our basic understanding of space and time and, respectively, matter, energy and causality —arguably to a no lesser extent. But we have not been able to combine these new insights into a novel coherent synthesis, yet. The XX century scientific revolution opened by GR and QM is therefore still wide open. We are in the middle of an unfinished scientific revolution. Quantum Gravity is the tentative name we give to the “synthesis to be found”.
In fact, our present understanding of the physical world at the fundamental level is in a state of great confusion. The present knowledge of the elementary dynamical laws of physics is given by the application of QM to fields, namely quantum field theory (QFT), by the particle–physics Standard Model (SM), and by GR. This set of fundamental theories has obtained an empirical success nearly unique in the history of science: so far there isn’t any clear evidence of observed phenomena that clearly escape or contradict this set of theories —or a minor modification of the same, such as a neutrino mass or a cosmological constant.1 But, the theories in this set are based on badly self contradictory assumptions. In GR the gravitational field is assumed to be a classical deterministic dynamical field, identified with the (pseudo) Riemannian metric of spacetime: but with QM we have understood that all dynamical fields have quantum properties. The other way around, conventional QFT relies heavily on global Poincar´e invariance and on the existence of a non–dynamical background spacetime metric: but with GR we have understood that there is no such non–dynamical background spacetime metric in nature.
In spite of their empirical success, GR and QM offer a schizophrenic and confused understanding of the physical world. The conceptual foundations of classical GR are contradicted by QM and the _conceptual foundation of conventional QFT are contradicted by GR. Fundamental physics is today in a peculiar phase of deep conceptual confusion.
And Roger Penrose has made these observations:


The following quote is from Roger Penrose celebrating Stephen Hawking’s 60th birthday in 1993 at Cambridge England.....this description offered me a new insight into quantum/classical relationships:

..Either we do physics on a large scale, in which case we use classical level physics; the equations of Newton, Maxwell or Einstein and these equations are deterministic, time symmetric and local. Or we may do quantum theory, if we are looking at small things; then we tend to use a different framework where time evolution is described.... by what is called unitary evolution...which in one of the most familiar descriptions is the evolution according to the Schrodinger equation: deterministic, time symmetric and local. These are exactly the same words I used to describe classical physics.

However this is not the entire story..... In addition we require what is called the "reduction of the state vector" or "collapse" of the wave function to describe the procedure that is adopted when an effect is magnified from the quantum to the classical level.....quantum state reduction is non deterministic, time-asymmetric and non local....The way we do quantum mechanics is to adopt a strange procedure which always seems to work...the superposition of alternative probabilities involving w, z, complex numbers....an essential ingredient of the Schrodinger equation. When you magnify to the classical level you take the squared modulii (of w, z) and these do give you the alternative probabilities of the two alternatives to happen...it is a completely different process from the quantum (realm) where the complex numbers w and z remain as constants "just sitting there"....in fact the key to keeping them sitting there is quantum linearity...
QUOTE]
and he goes on to relate this linearity and superposition to the double slit experiment.
 
  • #9
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must come some day....
 
  • #10
marcus
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Did anyone read Lee Smolin's response to the Edge.org question: "What are you worried about?"
http://edge.org/response-detail/23778
==quote from edge.org, Lee Smolin==
Still, I don't believe quantum mechanics gives a complete description of nature. I strongly believe there is another, truer description, waiting to be discovered.
==endquote==

Now he has made a fairly detailed presentation of a proposal of a deeper theory underlying QM. They are doing computer simulations to see if it can generate realistic probabilities in simple situations.

Smolin's new book Time Reborn gives a lengthier description. It comes out in a month or so from now.

But this Perimeter Institute video gives a brief desription and explain the reasoning and motivation behind it. The video is quite recent: 26 February 2013. Just eleven days ago.

to get it, google "smolin pirsa"
or click on this:
http://pirsa.org/13020146/

The title of the video lecturer is The universe as a process of unique events.

He has discovered an elegant minimalist way in which regularities (physical laws) can EVOLVE, so there are no fixed eternal physical laws above or outside the universe. The laws are an evolving part of the universe like everything else. The model also generates probabilities. It is extremely simple. the question is, could it generate the same probabilities as quantum mechanics, and thus fit observation?
 
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  • #11
marcus
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Back in January when Inflector started this thread, I posted a very unenthused response. Now after watching Smolin's February Pirsa video, which is a very interesting talk, I have changed my mind.

Before I did not read the Edge 2013 Question response perceptively and I was thinking of earlier ideas of Smolin's along these lines that, it seemed to me, had not gone anywhere.
And the book with Roberto Unger that never seemed to get pubished. But now that has changed.

1. a coherent picture of the universe, containing evolving regularities (natural laws) has come to fruition, and it even seems to be testable. It's presented in the 26 February video lecture.

2. the book with Roberto Unger is finished and is being read by potential publishers (but not yet in press)

3. Smolin has his own book, Time Reborn, containing a simplified wide audience account of these ideas, that is actually being reviewed. It goes on sale in April.

So the situation has moved forward and I want to sit up and take notice.

the idea could be right or wrong, we don't know, but in any case it is interesting. It is also radically ANTI-MULTIVERSE. Nothing above or outside. Nothing causing stuff that is not itself reacted back on. Nothing happening without a sufficient reason. No purely random stuff (but still effective probabilistic stuff, quantum mechanical uncertainty can emerge, something I don't understand yet.) Physical law is subject to explanation like everything else. There is a kind of uncompromising pragmatic empirical spirit about the proposed world-system.

It's a clever scheme that puts all these things together.

Rob Myers is in the audience and IIRC he asks one or more respectful questions to which Smolin answers at length. Neil Turok the director at Perimeter is also in the audience, I don't recall whether he asks a question or makes a comment. The video may bear watching again. After re-reading and thinking about the Edge 2013 response that Inflector linked in post #1.
http://edge.org/response-detail/23778
http://pirsa.org/13020146/ (26 February video lecture)
https://www.amazon.com/dp/0547511728/?tag=pfamazon01-20&tag=pfamazon01-20
 
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  • #12
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Did anyone read Lee Smolin's response..........
Yes, I did and I did also read the recommanded link concerning the tuneling.

In one of the last paragraphs Smolin suggests that (citation) ... : "a complete theory of quantum phenomena must contain a theory of space and time..." (end of the citation).

So my stupid question: "How are actually the "psy" functions (representing the waves) related to positions and time?" Are they depending on position and time such that we arbitrarily have Psy = Psy(x, t)? Or are these Psy(x, t) the diverse representations in the quantum world of the speeds of the particles? Why do I ask so? In fact just because a non linear projection of the Lorentz-Einstein law of motion can be mathematically represented by a law which is very similar to the Schrödinger equation (You can check it if you want)!

What is the official situation today concerning the incorporation of spacetime into a quantum theory?
 
  • #13
marcus
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What is the official situation today concerning the incorporation of spacetime into a quantum theory?
"official":biggrin:

Probably the "incorporation of space-time into a quantum theory" is an ongoing creative process about which it is impossible to have an official report. In post #3, you mentioned the "role" of asking Mr. Naive questions. I really appreciate when people take on this role. Thanks.

My private assessment of the situation today is that the Plebanski action for geometry is very important because it does not need background geometry and it can be extended to include matter fields. So I think that one should listen to the two online talks by Alexander (26 Feb) and by Marciano (May). They are the highest risk talks of the season---about incorporating both matter and geometry in the same backgroundless action. There is also the December 2012 paper by Alexander Marciano Smolin.

It is known how to quantize the Plebanski action (and extensions of it) via triangulation.
 
  • #16
member 11137
"official":biggrin:
Don't misunderstand this "official". I just meant "the academic position", what is teached in universities... Nothing else. Otherwise, I want to tell you that the physicsforums are no more secure, safe and that for example, my account has been hacked.

That's the reason you wull never more heard from me.
 
  • #17
Fra
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A while since I was here.

Before I did not read the Edge 2013 Question response perceptively and I was thinking of earlier ideas of Smolin's along these lines that, it seemed to me, had not gone anywhere.

And the book with Roberto Unger that never seemed to get pubished. But now that has changed.
...
2. the book with Roberto Unger is finished and is being read by potential publishers (but not yet in press)

3. Smolin has his own book, Time Reborn, containing a simplified wide audience account of these ideas, that is actually being reviewed. It goes on sale in April.
I have been waiting for that book. Judging from how I perceived Smolins ideas to be scattered and drifting I was almost convinced he had lost the track (to my dissapointment)

If I can get my hands on that book i will definitely read it. My highest hopes are on Unger to guide Smolins sometimes incoherent but more technical ideas (as I perceived it) in a fruitful direction.

Physical law is subject to explanation like everything else.
Yes indeed, but so far the sense I get from Smolins response in the edge post does not look (from my information abstracted perspective) too promising. But I REALLY look forward to the book!

Do you have any info on it? isbn number? where can we get it eventually?

/Fredrik
 
  • #18
marcus
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for goodness sake, Fra, google "pirsa smolin" and watch his video TALK about this.
It is far more specific, and interesting, than the Edge response.

The Edge response is just a vague teaser for what he is talking about with actual diagrams and stuff in his video talk.

The book is on Amazon (for pre-order). you merely google the book title "Time Reborn"
together with what information you think appropriate, like
"amazon smolin time reborn"

I don't KNOW that the book will be as specifically interesting to you as the pirsa video talk.
the talk is for fellow scientists and focused on the new ideas, it is not for popular wide audience.

If you have any trouble getting the video talk, please let me know and I'll help.

Haven't seen you for quite a while! Hope you are well and keeping busy :-D

Oh, here is the PIRSA link:
http://pirsa.org/13020146/
"The universe as a process of unique events"
 
  • #19
Fra
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Thanks Marcus for the direct pointer! I'll check that out!

Yes I'm doing well just too much to do to be omnipresent unfortunately. I hope you're well too!

/Fredrik
 
  • #20
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Very interesting and promising direction. As an outsider coming to physics as an accomplished adult about six years ago, I found the baseline assumption of many physicists that quantum reality is fundamental and therefore that causality is an emergent phenomenon to be misguided, at best. After all, how does causality emerge from an acausal substrate? Sort of like building with sand and no binder to hold the sand together.

It also strikes me that deBroglie-Bohm demonstrated that this was not necessary, so I have always been puzzled at the mass adoption of the quantum-reality-is-fundamental perspective.

So going back to causality as fundamental is, at the very least, a better philosophical foundation.
 

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