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What does 'emergent' mean in a physics context (split from Information Paradox)


StringJunky
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8 hours ago, StringJunky said:

Yes, I'll go with those. The sudden part is where I implied jokingly  'magic'... it just seems to appear.

I am not sure if I proposed an atom bomb explosion as an emergent phenomenon back along but the echange at 'critical mass' is such a change.

(Just fancied a change from my arch as a conversation subject)

:)

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14 hours ago, Markus Hanke said:

 

Ok, but who is to say that “fundamental” necessarily has to be absolute and global? My thoughts were that ‘fundamental’ might be scale-dependent, so that laws can form a hierarchy, wherein each set of laws is fundamental on that level. So basically fundamental to me would mean irreducible. In that picture, nature would come about as a set of strata, ie a multi-level hierarchy of laws, each one of which being irreducible. Each lower level would then form a boundary condition of the next higher level, but does not uniquely determine it.

 

So are you describing an approach where holistic (high-order) phenomena have causal powers somehow above and beyond one micro-constituent interacting with an adjacent one?  For example, on a macro level, could you have a fundamental law in which there is downward causation through lower levels?  A popular example is a mind having the thought to take some action - this is viewed, by strong emergentists, as thoughts having causal power with downward causation through lower levels (neurons, synapses, action potentials, etc.).  This thought-event is not uniquely determined by the lower levels, but happens as a more global process that is somehow irreducible.  I am not asserting any of this as valid, just (like you) exploring some implications.

 

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12 minutes ago, TheVat said:

A popular example is a mind having the thought to take some action - this is viewed, by strong emergentists, as thoughts having causal power with downward causation through lower levels (neurons, synapses, action potentials, etc.) ... I am not asserting any of this as valid, just (like you) exploring some implications.

Mind affecting brain would mean that atoms and molecules disobey laws of physics, unless mind is a new fundamental field.

(Exploring implications as well.)

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53 minutes ago, studiot said:

I think that 'cause' and 'scale' are extraneous parameters that do not bear upon 'emergence' or have at best only the loosest of connection to it.

I think so as well. I propose here a different approach:

A phenomenon appears emergent to us if it emerges as a consequence of some mathematical "hocus-pocus" rather than a straightforward result of other laws.

Such are all statistical phenomena: entropy, statistical distributions, blackbody radiation, Bose-Einstein condensate, superfluidity, superconductivity, ...

Such are conservation laws emerging, via Noether theorem, from symmetries of the system's Lagrangian.

Such is even a familiar phenomenon that solid materials do not collapse in on themselves or on each other. There is nothing emergent about it when it is erroneously explained by electrostatic repulsion of outer electrons in atoms. But it is emergent when viewed correctly as a consequence of Pauli exclusion principle, which in turn is a manifestation of antisymmetry of fermionic wavefunctions. 

Existence of mater and anti-matter is an emergent phenomenon too, because it is a required in order for quantum wave equations to be Lorentz invariant.

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7 minutes ago, Genady said:

I think so as well. I propose here a different approach:

A phenomenon appears emergent to us if it emerges as a consequence of some mathematical "hocus-pocus" rather than a straightforward result of other laws.

Such are all statistical phenomena: entropy, statistical distributions, blackbody radiation, Bose-Einstein condensate, superfluidity, superconductivity, ...

Such are conservation laws emerging, via Noether theorem, from symmetries of the system's Lagrangian.

Such is even a familiar phenomenon that solid materials do not collapse in on themselves or on each other. There is nothing emergent about it when it is erroneously explained by electrostatic repulsion of outer electrons in atoms. But it is emergent when viewed correctly as a consequence of Pauli exclusion principle, which in turn is a manifestation of antisymmetry of fermionic wavefunctions. 

Existence of mater and anti-matter is an emergent phenomenon too, because it is a required in order for quantum wave equations to be Lorentz invariant.

You have put forward a large collection of phenomena as emergent.
So I look forward to your elaboration as to why they are emergent  in support.

:)

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1 minute ago, studiot said:

You have put forward a large collection of phenomena as emergent.
So I look forward to your elaboration as to why they are emergent  in support.

:)

They are emergent, according to the proposed approach, because they are consequences of some mathematical "hocus-pocus" rather than straightforward results of other laws.

No, I cannot clearly define "hocus-pocus" vs. "straightforward". Maybe these are not objective attributes, but rather how the things appear to us.

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1 hour ago, Genady said:

They are emergent, according to the proposed approach, because they are consequences of some mathematical "hocus-pocus" rather than straightforward results of other laws.

No, I cannot clearly define "hocus-pocus" vs. "straightforward". Maybe these are not objective attributes, but rather how the things appear to us.

Personally I don't think that's good enough support.

Can you not take one of these proposals and say what characteristic of emergence it matches and under what circumstances.

'Hocus Pocus' belongs on the Magic Circle website, not the Physics section of SF.

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3 minutes ago, studiot said:

Personally I don't think that's good enough support.

Can you not take one of these proposals and say what characteristic of emergence it matches and under what circumstances.

'Hocus Pocus' belongs on the Magic Circle website, not the Physics section of SF.

Sorry, no, I cannot. This is the only characteristic of emergence I assume: not to be a result of direct application of other laws, but to be a consequence of some elaborate and not obvious mathematical construction built upon other laws.

In the examples above these constructions are: statistics, Noether theorem, antisymmetry of fermionic wavefunctions, and Lorentz invariance of wave equations.

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5 hours ago, TheVat said:

So are you describing an approach where holistic (high-order) phenomena have causal powers somehow above and beyond one micro-constituent interacting with an adjacent one?

Well, kind of. But I haven’t, in my own mind, arrived at a rigorous definition of the concept just yet.

5 hours ago, TheVat said:

For example, on a macro level, could you have a fundamental law in which there is downward causation through lower levels?

I don’t know the answer to this - personally I prefer to think of the lower levels as kind of a boundary condition to the ‘higher’ laws. Consider, for example, the laws of evolution - clearly, they are closely connected to lower levels, but are they determined by them? Can you start off with - say - statistical mechanics, and eventually arrive at the laws of evolution, perhaps through a simulation? Or how about the laws of psychology, sociology, or macroeconomics? Are they derivable from, say, the Standard Model? 

I think these are important questions to ponder.

Edited by Markus Hanke
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42 minutes ago, Markus Hanke said:

Well, kind of. But I haven’t, in my own mind, arrived at a rigorous definition of the concept just yet.

I don’t know the answer to this - personally I prefer to think of the lower levels as kind of a boundary condition to the ‘higher’ laws. Consider, for example, the laws of evolution - clearly, they are closely connected to lower levels, but are they determined by them? Can you start off with - say - statistical mechanics, and eventually arrive at the laws of evolution, perhaps through a simulation? Or how about the laws of psychology, sociology, or macroeconomics? Are they derivable from, say, the Standard Model? 

I think these are important questions to ponder.

Is this a bit analogous to chaos theory where systems are deterministic  in principle but not in practice?

 

And ,as someone said above does it make more sense to view emergence as being an phenomenon of perception?

(If that is the case there may never be a satisfactory answer because understanding our own nature** is subject to the law of diminishing returns.)

Are all transactions in macro systems mediated according to laws of quantum mechanics   but perceived according to the models we make  to understand them?

**are we first and foremost creatures that seek to learn?

 

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6 hours ago, TheVat said:

For example, on a macro level, could you have a fundamental law in which there is downward causation through lower levels?

As to emergence there is, I think, a dilemma between principle and practice that I think overrides almost any other consideration. Directionality of emergence is very clear in principle, but there are insurmountable difficulties in practice to ellucidate causation.

Atoms make a dog.

Dogs don't make an atom.

It's what Weinberg called 'arrows of explanation.'

That's very clear in principle. Even though it's impossible in practice to tell anything about dogs from the laws of atomic motion. It's very clear to me that dogs emerge from atoms; atoms do not emerge from dogs. I happen to know that some very philosophically-minded people think otherwise, which are the ones that @TheVat characterises as 'strong emergentists.' I think they can do that, only because the 'arrows of explanation' are invisible to all intents and purposes. It's a hopeless problem, so there is room for people to exploit this practical disconnect, interpret it as fundamental, and what's more, invert the 'arrows of explanation.' In this example,

7 hours ago, TheVat said:

A popular example is a mind having the thought to take some action - this is viewed, by strong emergentists, as thoughts having causal power with downward causation through lower levels (neurons, synapses, action potentials, etc.).

I think people who hold this view are disregarding an approach that's much more plausible: feedback mechanisms. Those are compatible with molecular determinism, IMO. Even though they're extremely complex.

 

1 hour ago, Markus Hanke said:

Can you start off with - say - statistical mechanics, and eventually arrive at the laws of evolution, perhaps through a simulation?

 

1 hour ago, Markus Hanke said:

Or how about the laws of psychology, sociology, or macroeconomics? Are they derivable from, say, the Standard Model? 

An algorithm to run on a machine that proved beyond any doubt that there must be such a thing as a dog based on the quantum laws of motion. That would be a sight to behold. But I wouldn't wanna be the person analising the data. This would-be machine would have to prove the logical necessity (from the atomic laws, to be kept in mind) of giraffes, and T-rex, and gut bacteria, and... covering all the organisms that ever were, that ever will be, and that would have been.

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9 hours ago, joigus said:

As to emergence there is, I think, a dilemma between principle and practice that I think overrides almost any other consideration. Directionality of emergence is very clear in principle, but there are insurmountable difficulties in practice to ellucidate causation.

Atoms make a dog.

Dogs don't make an atom.

It's what Weinberg called 'arrows of explanation.'

That's very clear in principle. Even though it's impossible in practice to tell anything about dogs from the laws of atomic motion. It's very clear to me that dogs emerge from atoms; atoms do not emerge from dogs. I happen to know that some very philosophically-minded people think otherwise, which are the ones that @TheVat characterises as 'strong emergentists.' I think they can do that, only because the 'arrows of explanation' are invisible to all intents and purposes. It's a hopeless problem, so there is room for people to exploit this practical disconnect, interpret it as fundamental, and what's more, invert the 'arrows of explanation.' In this example,

I think people who hold this view are disregarding an approach that's much more plausible: feedback mechanisms. Those are compatible with molecular determinism, IMO. Even though they're extremely complex.

 

 

An algorithm to run on a machine that proved beyond any doubt that there must be such a thing as a dog based on the quantum laws of motion. That would be a sight to behold. But I wouldn't wanna be the person analising the data. This would-be machine would have to prove the logical necessity (from the atomic laws, to be kept in mind) of giraffes, and T-rex, and gut bacteria, and... covering all the organisms that ever were, that ever will be, and that would have been.

Very interesting and perceptive comments added to the discussion. +1

The Principle of Reversibility.

 

Can you also incorporate the Reciprocal Theorem somehow ?

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11 hours ago, joigus said:

As to emergence there is, I think, a dilemma between principle and practice that I think overrides almost any other consideration. Directionality of emergence is very clear in principle, but there are insurmountable difficulties in practice to ellucidate causation.

Atoms make a dog.

Dogs don't make an atom.

It's what Weinberg called 'arrows of explanation.'

That's very clear in principle. Even though it's impossible in practice to tell anything about dogs from the laws of atomic motion. It's very clear to me that dogs emerge from atoms; atoms do not emerge from dogs. I happen to know that some very philosophically-minded people think otherwise, which are the ones that @TheVat characterises as 'strong emergentists.' I think they can do that, only because the 'arrows of explanation' are invisible to all intents and purposes. It's a hopeless problem, so there is room for people to exploit this practical disconnect, interpret it as fundamental, and what's more, invert the 'arrows of explanation.' In this example,

I think people who hold this view are disregarding an approach that's much more plausible: feedback mechanisms. Those are compatible with molecular determinism, IMO. Even though they're extremely complex.

 

 

An algorithm to run on a machine that proved beyond any doubt that there must be such a thing as a dog based on the quantum laws of motion. That would be a sight to behold. But I wouldn't wanna be the person analising the data. This would-be machine would have to prove the logical necessity (from the atomic laws, to be kept in mind) of giraffes, and T-rex, and gut bacteria, and... covering all the organisms that ever were, that ever will be, and that would have been.

There is another possibility in addition to the two directions of explanation being either bottom-up or top-down. The explanations of the laws on all levels could come from the same direction or from the same principles. For example, symmetry principles. Such principles are level independent and apply to all levels of phenomena, i.e. dogs, atoms, galaxies, etc.

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4 hours ago, studiot said:

Very interesting and perceptive comments added to the discussion. +1

The Principle of Reversibility.

 

Can you also incorporate the Reciprocal Theorem somehow ?

Thank you. I suppose you mean logical reversibility... 

I can see no reason why you couldn't in principle prove (work for another supercomputer) that given that there are dogs, there must be something like atoms. Seems to me that it would be far more difficult to do, though. I don't know if that can be formulated as a theorem either.

Suppose this: You feed the data to the supercomputer that there must be dogs. But dogs is not enough. You feed the data that there must be gut bacteria and black holes (interpolate from three different scales). The SC starts crunching numbers and.. bingo ==> There must be atoms that couple with a certain range of coupling constants, and so on. That's not impossible. Sounds reasonable. But atoms give dogs, and gut bacteria, and black holes seems inscapable. That's within the range of what I called 'in principle.'

2 hours ago, Genady said:

There is another possibility in addition to the two directions of explanation being either bottom-up or top-down. The explanations of the laws on all levels could come from the same direction or from the same principles. For example, symmetry principles. Such principles are level independent and apply to all levels of phenomena, i.e. dogs, atoms, galaxies, etc.

Yes, I'm aware of your observation before. The problem with this, I think, is that there are so few conservation laws that, as soon as the system goes above 3 degrees of freedom, you've got chaos. And chaos displays emergent structures (strange attractors, Studiot's catastrophic points --think phase transitions, etc.--) that are not related with conservation laws AFAIK, and I think it's safe to assume, as far as anybody knows.

A discussion of what is a symmetry and what's not would lead us far too far, but I think has to do with why your point is missing something. Is there a way to interpret non-analitically-integrable variables as obeying some kind of hidden symmetry that we haven't been able to recognise so far just because it's not one of the garden-variety symmetries that we know and love?

Edited by joigus
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14 hours ago, joigus said:

wanna be the person analising the data. This would-be machine would have to prove the logical necessity (from the atomic laws, to be kept in mind) of giraffes, and T-rex, and gut bacteria, and... covering all the organisms that ever were

Can  a baby step be taken?Can it be shown that the smallest imaginable system can arise out of some more fundamental process?

In a deterministic ,reproducible way...

 

(Not sure what I am asking,but we agree surely that the links between an individual  quark and the movement of the left ear of a giraffe are impossible to show in practice  and perhaps in principle)

 

I think the idea I think someone may have brought up.of replacing spacetime distances with other forms of correlation  sounds very interesting (exciting?)

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12 minutes ago, geordief said:

Can  a baby step be taken?Can it be shown that the smallest imaginable system can arise out of some more fundamental process?

In a deterministic ,reproducible way...

I think it can, and I think it has --promising steps-wise.

1) Chaos with strange attractors.

2) Theory (and experiments) on open systems with structure formation or so-called self organisation.

It is key in these systems that they are open --they exchange energy, momentum, and angular momentum with their surroundings. That's also another reason why I think the path is not following the traditional conservation laws, but other organising mathematical entities, perhaps based on hidden correlations. 'Hidden' here means we still don't know what they are.

Edited by joigus
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1 hour ago, joigus said:

as soon as the system goes above 3 degrees of freedom,

To correct myself: as soon as the system is above 2 degrees of freedom and the evolution equations are non-linear (@studiot mentioned it before.) ==> We've got chaos.

1 hour ago, joigus said:

Suppose this: You feed the data to the supercomputer that there must be dogs. But dogs is not enough. You feed the data that there must be gut bacteria and black holes (interpolate from three different scales). The SC starts crunching numbers and.. bingo ==> There must be atoms that couple with a certain range of coupling constants, and so on. That's not impossible. Sounds reasonable. But atoms give dogs, and gut bacteria, and black holes seems inscapable. That's within the range of what I called 'in principle.'

As a thought byproduct that might be relevant: It's interesting to notice that, in a way, that's what the Classical atomists, like Democritus, Leucippus, and Lucretius did: Given that there are these things and there are these behaviours (Democritus' clepsydra,) it stands to reason that the world is made of atoms.

Now that's not an algorithm, but use of common --if learned-- intuition. How does intuition lead you to a well-founded hypothesis about what things are made of? Maybe some day we can teach intuition to computers, amplifying their reasoning abilities.

Do I digress?

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On 1/9/2022 at 7:26 AM, joigus said:

That's very clear in principle. Even though it's impossible in practice to tell anything about dogs from the laws of atomic motion. It's very clear to me that dogs emerge from atoms; atoms do not emerge from dogs. I happen to know that some very philosophically-minded people think otherwise, which are the ones that @TheVat characterises as 'strong emergentists.' I think they can do that, only because the 'arrows of explanation' are invisible to all intents and purposes. It's a hopeless problem, so there is room for people to exploit this practical disconnect, interpret it as fundamental, and what's more, invert the 'arrows of explanation.' In this example,

Interesting and very valid thoughts. Thank you!

11 hours ago, joigus said:

I can see no reason why you couldn't in principle prove (work for another supercomputer) that given that there are dogs, there must be something like atoms.

I think all you could prove is that the dog isn’t infinitely divisible - it must be made of constituents that interact in certain ways. However, I don’t think you can determine the nature of these constituents via a top- down approach; if I was to somehow replace every single atom of the dog with a nano-machine that interacts with its environment in the same way an atom would, then nothing should change - you’d still have the same dog. I know this is controversial, but I don’t see what could possibly be different about the dog as a whole. 

10 hours ago, joigus said:

That's also another reason why I think the path is not following the traditional conservation laws, but other organising mathematical entities, perhaps based on hidden correlations. 'Hidden' here means we still don't know what they are.

The question that arises then is why simple systems should organise themselves into vastly more complex ones. It is interesting to note that the universe at large is a sea of increasing entropy interspersed with islands of low entropy - which is what living ecosystems fundamentally are. Left alone, these islands of low entropy grow and spread about, and it is not immediately obvious why that should be so, given the principle of least action.

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In an affort to stay on the topic of emergence, I looked carfully at the Wikipedia entry on emergence.

https://en.wikipedia.org/wiki/Emergence

It looks like other members have also looked there since I note several terms (words and phrases) that have been mentioned here.

Two things stands out.

A)

Apart from also discussing emergence in non scientific contexts, Wiki offers several ancient and also very modern contradictory accounts and definitions of emergence in the the Sciences.

B)

About the only characteristic of these different emergent characteristics seems to be the notion of emergence being the result of a combination/interaction of parts which do not themselves possess this characteristic.

This second point begs the immediate questions

  1. How many parts are required?
     
  2. Is the process reversible? That is can the emergence disappear if we revert to a collection of the parts?
     
  3. Can we actually revert to or recover the original parts?

However though Wiki is rich in general statements, it is poor in detailed examples.

So taking my exples of an arch and an atom bomb and comparing them I note

For the arch the answers are

  1. Minimum 1,  no upper limit
  2. Yes the parts may be deconstructed and reconstructed as many times as required
  3. Yes

For the atom bomb

  1. Many parts are required. The actually number is statistically detemined.
  2. No
  3. No The actual parts are destroyed in the emergence

 

 

 

 

 

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On 1/10/2022 at 2:51 AM, Markus Hanke said:

I think all you could prove is that the dog isn’t infinitely divisible - it must be made of constituents that interact in certain ways. However, I don’t think you can determine the nature of these constituents via a top- down approach; if I was to somehow replace every single atom of the dog with a nano-machine that interacts with its environment in the same way an atom would, then nothing should change - you’d still have the same dog. I know this is controversial, but I don’t see what could possibly be different about the dog as a whole. 

I've been pondering this for quite a while. I'm not enamoured of the 'inverse' approach, but I don't think it's impossible. But the way I see it, you would need more 'points' to interpolate. Levels of self-organization appear at different scales --already I know @studiot doesn't find this plausible--. Let's say: cells, multi-cellular organisms, planetary biota, and so on. At stellar level you would reach the point where no longer is there self-organisation. Instead, what you get is qualitatively different systems that, not only don't give rise to self-organisation, but actually erase information from their environment, and give it back to the universe completely thermalised (collapsing stars).

I'm not saying it's plausible, I'm just saying the next Boltzmann of this world may be able to outline something like that.

On 1/10/2022 at 2:51 AM, Markus Hanke said:

The question that arises then is why simple systems should organise themselves into vastly more complex ones. It is interesting to note that the universe at large is a sea of increasing entropy interspersed with islands of low entropy - which is what living ecosystems fundamentally are. Left alone, these islands of low entropy grow and spread about, and it is not immediately obvious why that should be so, given the principle of least action.

Very interesting. Let me keep thinking about this. One difficult aspect about the principle of least action is that, while its application is quite useful and simplifying in many cases, its meaning is obscure at best. It's a very abstract principle of physics.

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17 hours ago, joigus said:

Levels of self-organization appear at different scales --

I would tend to agree.

17 hours ago, joigus said:

Instead, what you get is qualitatively different systems that, not only don't give rise to self-organisation, but actually erase information from their environment

Good point!

 

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On 1/12/2022 at 4:23 AM, joigus said:

One difficult aspect about the principle of least action is that, while its application is quite useful and simplifying in many cases, its meaning is obscure at best. It's a very abstract principle of physics.

I remember that stationary action "emerges" from the Feynman path integral. Doesn't QM "explain" it?

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7 hours ago, Genady said:

I remember that stationary action "emerges" from the Feynman path integral. Doesn't QM "explain" it?

The principle of least action is a general principle of nature, which applies both in the classical and the quantum domain. It says that a given system will evolve such that the variation of the ‘action’ - a quantity which equals the time integral of the Lagrangian of the system (being the difference between kinetic and potential energy) - vanishes, ie it is stationary. This is equivalent to the Euler-Lagrange equation. Hence, to find the evolution equation of a system, you can first work out its Lagrangian, and then make the variation of the action vanish. For example, the Einstein equations emerge in this way from the Hilbert action.

This is amongst the most fundamental and most powerful known principles in physics.

Edited by Markus Hanke
Change extremum -> vanishing variation
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