Unification and Emergence in Physics: the Problem of Articulation by Ian Durham

Hi Ian,

Your essay raised a lot of interesting questions -- but if left me wanting some answers! Which side of the questions in section V do you tend to come down on? Your only "emphatic" answer, asserting that physicists should seriously think about these questions, was only preaching to the choir in my case... So although it was a major point you were trying to get across, I unfortunately can't report on how persuasive you would have been if I didn't already agree!

I found it interesting that you treated the Pauli Exclusion Principle and entanglement as distinct "seemingly strange" concepts; in my mind they tend to be lumped together, where the PEP is a special case of entanglement... but maybe I do need to think about global (anti)symmetrization rules independently.

One nitpick: "We also know that on the microscopic level there are processes that are fully reversible..." That makes it sound like there are a whole host of microscopic processes that are irreversible, when in fact if you zoom in sufficiently, *all* the known laws of physics are time-symmetric (or at least CPT symmetric). As your Partovi quote indicates, one can't really talk about the foundations of reversibility/irreversibility without discussing boundary conditions explicitly, as distinct from the laws themselves.

I need to think more about superselection rules as well... Thanks for bringing them up in this context.

Cheers!

Ken

Ken,

Actually, my point was precisely *not* to address the specific issues I discussed. Rather my point was that there is this missing step of articulation that we too often miss in our work. As such, while the reaction may be that I'm "preaching to the choir," the reality is (and I'm not necessarily singling you out - in fact I think you are much better than most people here) we don't practice what we preach.

So, in regard to section V, I don't think I have formed an opinion yet on many of these issues, but what I am saying is that they need to be addressed. I am, however, taking a clear stand on one issue, though it may appear to be a subtle one: physicists need to consider language and the foundations of mathematics. Not all physicists would agree with that claim.

Ian

Hi Ian.

Interesting essay, but just one point; some grail has recently been found, it wasn't where most were looking, and it needed different eyes to recognise it.

Interestingly it was where Einstein said it would be; "we can't solve problems by using the same kind of thinking we used when we created them". It also met your own criteria of not being "difficult to explain" (also of course as Einstein predicted).

Unfortunately, however beautiful, well evidenced and symmetric, the new way of thinking may still be a problem for most in perceiving it. If you'd like to try just follow the links under essay 495. It doesn't put the missing jigsaw peices together, but shows the picture on the box lid. It includes a key quantum mechanism that works with the postulates of SR.

Best wishes and best of luck.

Hi Ian -- Some confusions/questions:

- I'm confused right away by "taxonomic and statistical" vs. "procedural." How are the life sciences not procedural? There may be a technical sense in which you're using this word that I'm unfamiliar with, or I might just be processing this wrong. Anyway, it confused me. I know you clarify this somewhat in the next sentence, but it was still an unclear distinction to me. Is this a common distinction in philosophy of science?

- You use "theory of everything" in a way counter to the prevailing sense one finds it in the literature. Usually people take it to mean a strictly microscopic description, a la the usual reductionist bias in particle physics. I think it's important to make a distinction here between a "theory of everything" in the microscopic sense (which how I think most folks use this term), and one in the more general sense you use, in which problems of emergent phenomena and strong coupling physics have been solved. Indeed, it may be useful to distinguish between problems of extrapolating macro from micro, and problems of understand strongly coupled systems. These are different (though sometimes related) problems. Would you say that QCD is not a theory of the strong interactions because we don't know the dynamics of confinement? Most people I know would say that it is, and that we are just still trying to understand the low-energy dynamics.

- At the top of p. 3, you call the strong nuclear force "higher order," and say that its mediator is the meson. This is a little misleading -- the mediator of the strong force is the gluon (as you say earlier). Sometimes people use "nuclear force" to describe the force between hadrons, and this force can effectively be described as being mediated by pi and rho mesons. There are lots and lots of mesons in the world (most of which are very unstable, of course), so saying that this force is mediated by "the meson" is confusing to me. Also, you describe this force as "higher order," which sounds like a technical claim but is not precise. It's not like this is a subleading force in any expansion parameter, it's merely the avatar of the strong force once quarks have confined. I would remove the words "higher order" and replace them with something a la "low-energy effective."

- In Section III, you use the term "interaction picture." I think you just mean that this is the model where forces are described via exchanging messenger bosons. However, "interaction picture" is a technical term used to describe as particular picture of time evolution, just like the Schroedinger picture or Heisenberg picture. Of course, it's important for building up the exchange picture you're talking about, but I don't think they're synonymous. Are they? Anyway, this was a bit confusing to me.

Anyway, I hope these comments are at least a little useful. Also, I apologize if I'm just correcting stuff you already know but toned down deliberately for an article directed towards a non-technical crowd. I enjoyed reading this -- thanks!

B

Brian,

Thanks for the great comments.

> - I'm confused right away by "taxonomic and statistical" vs.

> "procedural." How are the life sciences not procedural? There may be

> a technical sense in which you're using this word that I'm unfamiliar

> with, or I might just be processing this wrong. Anyway, it confused

> me. I know you clarify this somewhat in the next sentence, but it was

> still an unclear distinction to me. Is this a common distinction in

> philosophy of science?

I wrestled with that word 'procedural' for a long time but couldn't come up with anything better. The life sciences are certainly partly procedural, but they are very clearly primarily taxonomic. I've been discussing this point with one of our biologists (who is actually a biochemist and thus straddles the boundary) and he agrees with me. In fact we're trying to implement this into our core curriculum. This is why, in some philosophy of science circles, physics is included in what is called the 'exact sciences.'

> - You use "theory of everything" in a way counter to the prevailing

> sense one finds it in the literature. Usually people take it to mean

> a strictly microscopic description, a la the usual reductionist bias

> in particle physics. I think it's important to make a distinction

> here between a "theory of everything" in the microscopic sense (which

> how I think most folks use this term), and one in the more general

> sense you use, in which problems of emergent phenomena and strong

> coupling physics have been solved.

Aha! My point exactly (though I clearly didn't articulate it well enough - so much for following my own advice). How can we use that term if it's only on a microscopic level that we truly mean it? And how, then, is it a fair representation of what we do if people like Brian Greene become household names in the process of muddling the distinction, i.e. Is it truly *everything* or just everything microscopic? Popularizers of science are not always clear on this point. Again, it's all about consistency in the language we use.

> Indeed, it may be useful to

> distinguish between problems of extrapolating macro from micro, and

> problems of understand strongly coupled systems. These are different

> (though sometimes related) problems. Would you say that QCD is not a

> theory of the strong interactions because we don't know the dynamics

> of confinement? Most people I know would say that it is, and that we

> are just still trying to understand the low-energy dynamics.

Hmmm. That's a really good question. I'd have to ponder it before I say one way or the other. But I will say that this relates to your next point a bit...

> - At the top of p. 3, you call the strong nuclear force "higher

> order," and say that its mediator is the meson. This is a little

> misleading -- the mediator of the strong force is the gluon (as you

> say earlier). Sometimes people use "nuclear force" to describe the

> force between hadrons, and this force can effectively be described as

> being mediated by pi and rho mesons. There are lots and lots of

> mesons in the world (most of which are very unstable, of course), so

> saying that this force is mediated by "the meson" is confusing to me.

> Also, you describe this force as "higher order," which sounds like a

> technical claim but is not precise. It's not like this is a

> subleading force in any expansion parameter, it's merely the avatar

> of the strong force once quarks have confined. I would remove the

> words "higher order" and replace them with something a la "low-energy

> effective."

This is one of my biggest pet peeves. Forget the names for the moment. We have interaction A that mediates between quarks and exchanges gluons. This is the interaction that holds nucleons together individually (not to mention mesons themselves), i.e. the reason nucleons exist to begin with. Interaction B mediates *between* the nucleons and exchanges mesons and thus binds the nucleons *to each other.* These are not only two different (though related) things, they are of different orders (or on different levels, if you will). Interaction B involves particles (including the exchange particles) that are *not* fundamental and that are held together by interaction A. Think of it in terms of Legos. Interaction A uses all the base Legos. Interaction B builds up something bigger using pre-assembled pieces. I call interaction A the color interaction while I call interaction B the strong nuclear interaction. Physicists tend to either intermingle these terms *or* use 'strong nuclear' to refer to both (or to gloss over the fact that there are actually *two* things going on here).

It's all about being as consistent in our description as we can be and what I'm saying is that, while nothing will ever be perfect, there is room for improvement and, in pushing ahead, we need to consider these points. I took on Frank Wilczek in Physics Today about this a few years ago regarding the definition of mass. I forgot to add to my letter, though, that my description of mass in that letter (as the magnitude of the four-momentum vector) is the only self-consistent definition for mass if we want to use the term for both point particles as well as extended objects (atoms, boxes, desks, etc.).

> - In Section III, you use the term "interaction picture." I think you

> just mean that this is the model where forces are described via

> exchanging messenger bosons. However, "interaction picture" is a

> technical term used to describe as particular picture of time

> evolution, just like the Schroedinger picture or Heisenberg picture.

> Of course, it's important for building up the exchange picture you're

> talking about, but I don't think they're synonymous. Are they?

> Anyway, this was a bit confusing to me.

Oops. Well, there goes any chance I had at winning a prize. Doh!

Ian

A first class assay with depth and breadth of content and a very readable presentation. Some comments:

1. I thoroughly agree about the importance of language. All truly great scientists recognise the crucial requirement to explain all science REASONABLY; i.e. in language a general educated & intelligent person can understand. This is the starting point for my essay but I merely note the importance of language and defer consideration of to another occasion. It is commendably one of the requirements of this competition (although the ratings don't seem to reflect that). Your essay, like the one by Norman Cook, is admirable in this respect. This general reader understood most of it and learned much.

2. For another view of "Stuff" - have a look at "Words without Objects" by Henry Laycock OUP 2006

3. Re Language & PEP Feynman is on record as saying that as we cannot explain the Spin-Statistics Theorem in simple Language we do not really understand it - in accordance with (1).

4. You write "Unfortunately this bumps up against REALITY in the form of incompleteness: fully axiomatized systems are logically impossible." and rely on Godel. Godel relies upon established maths and countable structures. These supports may not be as sound as you and everyone thinks.

5. Many essays here equate GUTs with TOEs - but don't even mention emergence.

6. Re QM you write " ... that new interpretations pop up regularly." I argue that the multiplicity of Interpretations renders Interpretation a Symptom only. For me the issue is representation - the Logic & Maths.

7. You write " .. is the question of whether or not our cherished conceptual notions are really conceptual at all." I list 10 specific points in my essay. The first one points out that logically particles cannot have a Velocity or a Kinetic Energy.

8. You write "On a practical level we may need to ask ourselves if mathematics is a sufficient language of description." I prefer the terminology "representation' to "description", and my essay concludes, based on the 10 points, that it is insufficient. Therefore maths needs augmenting; not lamenting !

Terry Padden was as usual Anonymous - but never gets both pay packets.

Dear Ian,

You raise relevant points which I have been struggling with for quite a long time. Physics, and especially its most fundamental part, must be expressed in plain language. I'll have to read Fortun and Bernstein.

I also think that we should question the paradigm that quantum / micro opposes classical / macro. This opposition emerged due to the classical context in which quantum mechanics was formulated, but is experimentally doubtful.

The reference to the exclusion principle is also pertinent. Science vulgarization focuses too often on four forces, of which we know how to unify three, etc, etc. But the day that we'll know how to unify gravity with the 3 other forces, we'll be confronted with a new challenge: explaining 'this non vanishing piece of junk' in terms of a physical process, and the whole search for a theory of everything will begin from start.

By the way, I promote the FQXi contest on my twitter profile and my blog. Would you mind if I post quotes of yours, linking to your essay?

Regards,

Arjen

Arjen, feel free to post quotes on Twitter and thanks!

I'm glad I seem to have raised some points deemed relevant. I have been busy but do intend to read the aforementioned essays.

Mr. Durham,

Thank you for this well written, thought provoking essay. Apropos of the thrust of your essay, as I understand it, is John Archibald Wheeler's comment that, "We have to learn how to use our words. It's a fantastic thing -- we humans are so easily trapped in our own words. The word time for instance -- we run into puzzles about the concept of time and then we say, oh, what a terrible thing. We don't realize we're the source of the puzzle because we invented the word . . . ."

Regarding your discussion of the reversibility of microscopic processes versus the irreversibility of macroscopic processes, I freely admit to being more than a little confused about this concept; you wrote, "We know there is a deep link between the notion of causality (and thus locality) and reversibility, yet we also know that on the microscopic level there are processes that are fully reversible. Nonetheless, the latter we tend to explain away by assuming that, as we scale up, processes become irreversible as the multiplicity increases [5, 6]."

As a brief thought experiment to help me understand this concept, please consider the case of a gas in a sealed container. First, would it be correct to say that dynamical processes in the sealed container (i.e., collisions between the gas molecules, for example) would fall under the general heading of microscopic, time reversible processes? If so, then if we assume that the sealed container is located on the Earth, which is hurtling through space in its orbit around the sun, which in turn is hurtling through space in its orbit around the center of our galaxy, can we still say that the processes taking place in the sealed container are really time reversible, i.e., can they be fairly considered in isolation from the larger dynamical context in which they exist? Or is this simply a case of me totally misunderstanding the question/problem? If the latter, I regret to say it wouldn't be the first time this has happened, and it probably won't be the last. Any clarification greatly appreciated.

Thanks again for a nice essay!

Cheers

OK, I have finally found a pause during which I can respond to some of these great posts.

> These supports may not be as sound as you and everyone thinks. [Re: Gödel]

I fell into my own trap by calling this 'reality.' It is a mathematical truth, but as I point out, there may be a limit to the use of mathematics in describing physical reality.

> Many essays here equate GUTs with TOEs - but don't even mention emergence.

This is one of my pet peeves.

> For me the issue is representation - the Logic & Maths. [Re: interpretation]

Right, but addressing the issues of representation ends up addressing some of the issues of interpretation. That's kind of my point - they're inextricably linked.

> "We have to learn how to use our words. It's a fantastic thing -- we humans

> are so easily trapped in our own words. The word time for instance -- we run

> into puzzles about the concept of time and then we say, oh, what a terrible

> thing. We don't realize we're the source of the puzzle because we invented

> the word . . . ."

Fantastic quote.

> First, would it be correct to say that dynamical processes in the sealed

> container (i.e., collisions between the gas molecules, for example) would

> fall under the general heading of microscopic, time reversible processes?

No, not in the aggregate. If you're talking about an individual gas molecule, then yes, but if you're talking about the whole gas, then that's macroscopic since it is macroscopically measurable in some sense. In other words, macroscopic properties arise from the aggregate behavior of microscopic processes. In one sense, irreversibility arises in this way. Think of a single coin flip. In and of itself, it's 50% perfectly reversible. Have more coin flips, either simultaneously or in sequence, and the probability that the sequence as a whole is reversible drops dramatically.

> can they be fairly considered in isolation from the larger dynamical context

> in which they exist?

Certainly not as a whole, but on extremely short time scales and over extremely short distances, they can be isolated (we do this all the time in order to solve problems). In truth, is anything *perfectly* reversible? Probably not, but to a great degree of precision some processes are extremely close because external interactions are so weak.

Thanks for the great comments!

ITD

Dr Durham,

I read your essay but it was next to impossible to comprehend the text. For me, it touches far too many points and it was beyond my intellectual capabilities to link these points into a coherent picture.

Since I thus have nothing general to say, let me make a few specific remarks:

1. You write [p 4]:"We know there is a deep link between the notion of causality

(and thus locality) and reversibility,". What exactly is this "deep link"?

2. You write [p 5]: "We like rules. Unfortunately this bumps up against reality in the form of incompleteness: fully axiomatized systems are logically impossible [12]." With respect, but this statement is nonsense. There are many fully axiomatized and complete logical systems. Goedel only showed that a complete axiomatization of logical systems which include number arithmetic is impossible.

3. You write [p 5]: "Nonetheless, macroscopic objects are quite clearly more physically complex than microscopic ones." Interesting assertion, but of what measure of "physical complexity" have you thought specifically? In what sense, for example, is the quantum field vacuum (and its fluctuations) less complex than a chair? I don't quite understand.

Dr. Lisewski,

> I read your essay but it was next to impossible to comprehend the text. For me, > it touches far too many points and it was beyond my intellectual capabilities > to link these points into a coherent picture.

Well, a lot of other people had no trouble comprehending it including a class of freshman undergraduates. Most other people also had no trouble understanding what the coherent picture was: in developing a unified theory physicists need to a) be consistent with their language (including the mathematics) and b) address the issue of emergence. The two points are brought together in the discussion of interactions where our language is neither fully unifying nor able to account for certain macroscopic phenomena.

> What exactly is this "deep link"?

Do a Google search on this topic or read some Davies, Eddington, Bohm, Leibniz, Popper, Clausius, etc, etc, etc. You could also read my PhD thesis (on the arXiv).

> With respect, but this statement is nonsense. There are many fully > axiomatized and complete logical systems. Goedel only showed that a complete > axiomatization of logical systems which include number arithmetic is > impossible.

Actually, there are multiple incompleteness theorems that Gödel developed. Not all include number arithmetic. Again, there's a lot of literature out there on attempts to axiomatize physics and its various pitfalls. I will admit that this is partially an 'educated' opinion on my part. But it's not out of the blue and I'm hardly the only one that holds this opinion.

> In what sense, for example, is the quantum field vacuum (and its > fluctuations) less complex than a chair? I don't quite understand.

Describe the chair in quantum field theoretic terms. It's far more complex in that sense than the quantum vacuum. The only reason it seems simpler is because you're using a different 'language' to describe it - classical versus quantum. But if we want to have a consistent description of the world - and we need one in order to understand emergent phenomena - we need one language that can describe everything. It doesn't mean ditching classical physics. Engineers aren't going to use quantum field theory to design a chair. But if our hope is to understand the link between classical and quantum, macro and micro, then we need one language. In this sense, I suppose I am anti-Bohrian (whatever that means - read Mara Beller's Quantum Dialogue).

Finally, why is it that physicists, mathematicians, and other such folk - theorists in particular - find the need to be rude and condescending when they are critical of something? One can be critical without being rude.

Pardon me, I never wanted to be rude. Every single point you make in your essay is in itself interesting but I think, given the contest's text length constraints, a little less would be more in your case.

Dear Ian,

I found your paper contained many very interesting and helpful questions and observations. I am not a physicist but venture a few comments.

First, I feel that the radical answer to the current crop of problems in physics is to recognize that physicists and physics are just as much part of the universal process as any other process. In particular, I would see the 'collapse of the wave function' and the human act of insight as isomorphic up to a scale factor. In other words the universe is intelligent in the same way as we are intelligent.

From a communication point of view, both insight and collapse are acts of coding, whose outputs and inputs are is a messages. These words are the message output of some of my own insights into physics derived from the inspection of thousands of pages of data and modelling. A particle of some sort is usually the output of a physical observation. Human talk and universal talk are abstractly the same.

By seeing the world as a communication network (the 'interaction picture') we get an explanation for quantization. As Shannon showed, the strategy for defeating error in communication is to encode messages into long strings or packets whose letters are equiprobable so that we can place packets as far apart as possible in message space, so minimizing the chances of confusion. This is quantization. Messages with no overlap are orthogonal, like quantum mechanical basis states.

This picture may resolve the macro micro quantum classical question. Wherever there is error free communication there is quantization, whatever the scale. We are led by the apparent continuity of motion to attribute continuity to the foundations of the universe. In fact nothing is continuous, and continua carry no information. At the most fundamental level, quantum field theory sees motion as a series of discontinuous creations and annihilations, and at the macroscopic level everything is broken up into pieces like letters, sentences, people, stars and so on.

From the communication point of view, we may see quantum mechanics as a method for computing the traffic in various channels in the universal network. The transition to quantum field theory introduces space and special relativity. One might see special relativity as a consequence of the delay induced by error defeating coding, since the channel must wait for the source to emit enough letters to form a packet before it transmits a signal.

Finally, the quantum network picture may also enable us to understand emergence in the universe. It seems reasonable to start with an initial singularity with no internal structure which, communicating with itself slowly builds up the universe as we know it. Like practical engineered communication networks, we see this network as layered, each layer charcterized by a certain set of software. We may see quantum mechanics as the lowest layer. As Zee notes (Nutshell page 16) (0 1)-dimensional quantum field theory is just quantum mechanics, ie quantum mechanics antedates space.

It seems clear that the origin of space has something to do with the Pauli Exclusion Principle. Following the computer network analogy, we might see space as memory and the exclusion principle as maintaining the orthogonality between independent memory locations. The selective advantage of remembering algorithms which enable error free communication thus somehow bootstraps the exclusion that makes independent memory possible. I can not see much further than this, but do suspect that space has become fixed at three dimensions because (as chipmakers, wirers and pipelayers know) three dimensions is the minimum space in which one can join many pairs of points without crossed wires.

The network picture may provide the 'missing conceptual layer in quantum physics. The universe is inherently dynamic, but, since it maps onto itself, is constrained by fixed point theorems, It is the fixed points in the dynamics which physicists seek, since, as Parmenides noted 2500 years ago, we cannot write a permanently true text about something that is changing. Mathematics turns out to be a good language for the expression of these fixed points.

All the best,

Jeffrey

Ian Durham,

it is truly a pity that i could find your nice essay to see so late. You have provided the freshness criteria for doing Physics and have rightly emphasised the need for articulate language to present the conceptual aspects of Physics. To me the conceptualization aspect is the most significant part of Physics, followed by a concise presentation of the same in a mathematical form, devoid of unnecessary mathematical jugglery. The experimnetation stands apart that finally seals the the theory as correct or reasonable. Howver. all these three approaches have scope for improvement as one attempts to appraoch better and better relative Physics.

May i request you to find the time to go through my essay site on this forum, as it may help me approach the subject with the benefit of the maturity you possess in the field. We all gain from one another and it is a separate human trait wheather we acknowledge other sources adequately or not. There comes the ethical aspect that is often ignored by scientists who are after name & fame. Science needs an impersonal touch from us all, as it is search for truth about the physical world/universe.

@Jeffrey: Seth Lloyd has some very similar ideas along these lines. It's an intriguing way to view the world around us. There's an alternate to it, though, that cuts more to the chase: if we allow that there are at least some objective, universal mathematical truths (number, for example) then mathematics is even more encompassing since, as a whole, mathematics is entirely self-consistent.

@Narendra: I will endeavor to read your essay and comment on it. Thanks for commenting on mine.

Re: Macro-not-necessarily-classical and Micro-not-necessarily-quantum.

If Harold Macmillan had been a scientist rather than a politician he might have said "Correlations, dear boy, correlations" instead of that famous bit about events. We may be engulfed all the time within entanglement or something doing a pretty good job of faking it. How else to "explain" the efficacy of statistical sampling, all the way from quality control management to political tracking polls? Why should a sample population be an ongoing microcosm of the general population? Etc.

As Diederik Aerts has demonstrated (and he personally ran this past both Bell and Aspect before initial publication back in 1981 ... Bell worried that it'd confuse people but didn't fault the science, and Aspect said, in effect, so big deal) you can even macroscopically violate BI by the simple expedient of connecting two buckets of water with a hose. Then, as they say, just do the math. No kidding. Actually this shouldn't be all that surprising. You get interference effects whether you're double-slit experimenting with hydraulics (purely coincidental relationship to the dihydrogen oxide mentioned above) or quanta. Arjendu Pattanayak tracks "classical" chaos well into the quantum realm. It's the interfaces that are fun. And doubtless where truth lurks.

(Interpreting the Aerts gedanken can lead to deep technical debate about the locality condition in Bell, but if Charles Tresser is right you don't need that assumption anyway. It's all about realism.)

Dear Ian,

An intriguing essay. The exchange of particles is described by probability waves just like the force generated by the Pauli exclusion principle. So they have something in common. Why is this Pauli exclusion principle force so different?

I always wondered how the force generated by the pauli exclusion principle is calculated. How big is it? How can it be that the gravitational force becomes bigger then this 'exclusion principle force'? What happens with the particles? Or are there no particles left, but all what left is space, time, mass and other continues substances? What happens with the probability waves?

Greetings

Peter