Sidney Coleman's opinion on interpretation in his Dirac lecture

[gentzen]

pines-demon quoted from Sidney Coleman's Dirac Lecture "Quantum Mechanics in Your Face" (https://arxiv.org/abs/2011.12671)

The other day I was looking at a British videotape of Feynman explaining elementary concepts in science to an interrogator, whom I think was the producer Christopher Sykes. He asked Feynman to explain the force between
magnets. Feynman hemmed and hawed for a while, and then he got on the right track, and he said something that’s dead on the nail. He said:

You’ve got it all backwards, because you’re not asking me to explain the force between your pants and the seat of your chair. You want me, when you say the force between magnets, to explain the force between magnets in terms of the kinds of forces you think of as being fundamental—those between bodies in contact.

Obviously, I’m not phrasing it as wonderfully as Feynman. But, well, as Picasso said in other circumstances, it doesn’t have to be a masterpiece for you to get the idea. We physicists all know it’s the other way around: the fundamental force between atoms is the electromagnetic force which does fall off as one over R squared. Christopher Sykes was confused because he was asking something impossible. He should have asked to explain the pants-chair force in terms of the force between magnets. Instead he asked to derive the fundamental quantity in terms of the derived one.

Likewise, a similar error is being made here. The problem is not the interpretation of quantum mechanics. That’s getting things just backwards. The problem is the interpretation of classical mechanics.

and martinbn added "the full quote" of what Sidney Coleman said before (and refers to here) to make things clearer:

“Every successful physical theory swallows its predecessor alive.” But it does so by interpreting the concepts of the old theory in terms of the new, NOT the other way around. Thus our aim is NOT “the interpretation of quantum mechanics.” It is the interpretation of classical mechanics.

Sidney Coleman's opinion on interpretation in these two quotes is:

• Thus our aim is NOT “the interpretation of quantum mechanics.” It is the interpretation of classical mechanics.
• The problem is not the interpretation of quantum mechanics. That’s getting things just backwards. The problem is the interpretation of classical mechanics.

However, more quotes are needed to capture Coleman's position in his Dirac lecture:

I want to stress that I have made no original contributions to this subject. There is nothing I will say in this lecture, with the exception of the carefully prepared spontaneous jokes—that was one of them—that cannot be found in the literature.

The position I am going to advocate is associated with Hugh Everett in a classic paper.

I will argue the there is

NO special measurement process​

NO reduction of the wave function​

NO indeterminancy​

NOTHING probabilistic​

in quantum mechanics.

ONLY deterministic evolution​

according to Schrödinger’s Equation​

Zurek has made major contributions to the theory of decoherence—where instead of just saying it’s ridiculous or absurd, he actually raised a question one can talk about. He said: “If this is so, why do I the observer perceive only one of the outcomes?” This is now the question I will attempt to address: Zurek’s question. If there is no reduction of the wave packet, why do I feel at the end of the day that I have observed a definite outcome, that the electron is spinning up or the electron is spinning down?
In order to ease into this, I’d like to begin with an analysis of Neville Mott.

In Tom Stoppard’s play Jumpers, there’s an anecdote about the philosopher Ludwig Wittgenstein.

Now people say the reduction of the wave packet occurs because it looks like the reduction of the wave packet occurs, and that is indeed true. What I’m asking you in the second main part of this lecture is to consider seriously what it would look like if it were the other way around—if all that ever happened was causal evolution according to quantum mechanics. What I have tried to convince you is that what it looks like is ordinary everyday life.

Sidney Coleman's position in these quotes is:

• I have made no original contributions to this subject.
• Zurek ... actually raised a question one can talk about.
• In order to ease into this, I’d like to begin with an analysis of Neville Mott.
• Now people say the reduction of the wave packet occurs because it looks like the reduction of the wave packet occurs, and that is indeed true.

The connection to the annecdote about Wittgenstein definitively was an original contribution. This raises the question whether it was the only original contribution. Another likely original contribution is his ambiguous reframing: "The problem is the interpretation of classical mechanics."

But I don't think Sidney Coleman was intentionally lying when he denied having made original contributions. The scientists mentioned in the quotes above are Neville Mott, Hugh Everett and Wojciech Żurek. (Other scientists are mentioned in: "Some of the things I’ll say about probability later come from a paper by Jim Hartle, and one by Cambridge’s own Eddie Farhi, Jeffrey Goldstone, and Sam Gutmann.") So I wonder whether his position can be justified as a non-original selection from published works of Mott, Everett and Żurek, or whether it must be considered as an original position, which was never peer-reviewed or even worked-out properly.

 

[Demystifier]

I don't know whether Coleman's position contains something original, but there is something else that I find problematic. Coleman first says that his aim is not the interpretation of QM, but then he says that he will advocate the Everett's position. Well, the Everett's position is an interpretation of QM. Moreover, it is very questionable how successful this interpretation is. It is certainly not the mainstream interpretation that most physicists use in practice, so it cannot be said that it is very successful in a practical sense. So, when he says

“Every successful physical theory swallows its predecessor alive.” But it does so by interpreting the concepts of the old theory in terms of the new, NOT the other way around. Thus our aim is NOT “the interpretation of quantum mechanics.” It is the interpretation of classical mechanics. (my bolding)

it is very questionable whether this can be applied to the Everett's view of QM.

What I'm really saying is this. I agree that every successful physical theory should interpret the concepts of the old theory in terms of the new, not the other way around. However, QM in general, and Everett's QM in particular, is still not successful enough. QM still contains open conceptual questions within itself, that's why we have various interpretations, each with some advantages and drawbacks. Hence QM is still not understood sufficiently well to present, with full confidence, the interpretation of classical mechanics in terms of quantum mechanics.

 

[haushofer]

It's comparable to the time where the geocentric and heliocentric models both successfully explained planetary orbits. It was only in accepting the heliocentric model that modern cosmology could develop. From this modern standpoint the heliocentric model of course is to be preferred.

Sometimes I get the feeling physicists think that this whole interpretational issue is just a luxury which won't bring us any further in the development op physics. I think that's a huge mistake, comparable to how the catholic church in Galilei's time thought you could just see the heliocentric model possibly as some useful tool without any ontological or scientific consequences.

 

[Demystifier]

It's comparable to the time where the geocentric and heliocentric models both successfully explained planetary orbits. It was only in accepting the heliocentric model that modern cosmology could develop. From this modern standpoint the heliocentric model of course is to be preferred.

Sometimes I get the feeling physicists think that this whole interpretational issue is just a luxury which won't bring us any further in the development op physics. I think that's a huge mistake, comparable to how the catholic church in Galilei's time thought you could just see the heliocentric model possibly as some useful tool without any ontological or scientific consequences.

If the geocentric model preferred by the catholic church is the metaphor for the orthodox interpretation of QM, then the heliocentric model is the metaphor for which interpretation of QM?

I would say it must be some realist interpretation, which does not put an observer into the "center of the universe". So the main candidates seem to be the many worlds interpretation, the Bohmian interpretation, the consistent histories interpretation, and the objective collapse interpretation. But I would rule out many worlds, because it is the most extreme example of mistaking the map for the territory. Next I would rule out the objective collapse interpretation, not because it is wrong, but because it is an alternative theory, so it is not really an analog of the heliocentric model. Finally, the consistent history interpretation holds that reality depends on the framework, which is analogous to a statement that any object can be taken as the origin of coordinates, not to a statement that it must be the Sun. So I conclude that the best analog of the heliocentric model is the Bohmian interpretation. (Which, of course, does not make it the right.)

 

[gentzen]

Coleman first says that his aim is not the interpretation of QM, but then he says that he will advocate the Everett's position. Well, the Everett's position is an interpretation of QM.

Careful, he only said "associated with Hugh Everett". Since Coleman is very careful with words, this means that he is not claiming to advocate for Everett's position.
And as John McAndrew remarked, Coleman gets asked if he is a follower of Everett’s Many Worlds interpretation at 1:04:20, and clarifies even more explicitly why he is very careful:

Yeah, but that's a tricky thing to say. That's like saying you're a Christian. I mean Everett wrote this one truly wonderful paper and then everyone got on their horse and rode off in all directions. The position I'm advocating is a position that (at least in my case) was certainly largely inspired by Everett's paper. Whether it's really Everett's position or not I would prefer not to discuss.

Peter Woit nicely captured the association between Coleman and Everett (in the comment above John McAndrew's):

Coleman explicitly does refer to Everett, and yes, he’s an Everettian in the sense of seeing no reason QM without a reduction postulate can’t describe the world as we know it. My point was just that he doesn’t invoke a splitting into “many worlds” to replace wave-function reduction.