Ed Witten on Symmetry and Emergence

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star apple
Hmmm...

This kind of "simple" emergence of spacetime geometry, in the perturbative approach from a classical geometry and a given topology is a very weak form of emergence that I dont think is not what Smolin means, and for sure not what i have in mind, without going into details.

Smolin generically talks about emergent statespaces in an evolutionary sense, but this is in his later books, i dont remember how far these ideas was expressed in the early books like three roads.
https://www.amazon.com/dp/1107074061/?tag=pfamazon01-20
https://www.amazon.com/dp/1107074061/?tag=pfamazon01-20

Thanks for mentioning this book. I didn't know he wrote this. I just bought one and it completes my collection of all Smolin books. I like the part where he mentioned:

"* the fundamental theory will not be quantum mechanical.. but quantum mechanics will emerge in the case of small subsystem.
* the fundamental theory will not exist in space, but space will be emergent in some eras of the universe."

Do you know of authors or papers where they explored the "dna of physical law" as you put it? Where there is perhaps some idea of elementals that embody certain forces of nature... this is the truly radical theory.. smolin stuff is just not radical or powerful enough to explain all of nature.

or
https://www.amazon.com/dp/0544245598/?tag=pfamazon01-20
or
http://pirsa.org/08100049/

The connection between "evolution of law", and the emergence of symmetry, and the concept of observer depdenent observer invariance as an hierarchy of observers, is probably not too easy to explain briefly simply because noone to my knowledge does it this way, but you can understand the vision maybe by as a synthesis of the below spirits exemplified by some quotes, like take the good parts of each, try to deform it to make it selfconsistent, dump the rest, and what do you get? ;-)

"However, the rules of classical probability theory can be determined by pure thought alone without any particular appeal to experiment (though, of course, to develop classical probability theory, we do employ some basic intuitions about the nature of the world). Is the sametrue of quantum theory?"
-- Lucien Hardy, https://arxiv.org/pdf/quant-ph/0101012.pdf

"Entropic dynamics, a program that aims at deriving the laws of physics from standard probabilistic and entropic rules for processing information, is developed further."
-- Ariel Caticha, https://arxiv.org/abs/0808.1260

The problematic common denominator of all the various statistical emergence problems is that they fail to give the appropriate observational physical footing to the probability spaces. One part of this is also how lightly the concept of uncountably many alternatives are introduces in the theory, becuase it destroys computability of the inference system. It also seems intuitive that finite physical systems does not encode infinite amounts of information. So why the need for continuum models? That is often easier to work with from the point of view of analytical appraoches, but computers prefer finite sets. And nature might well too, who knows?

Then add these ideas..

" We need determinism only in alimited set of circumstances, which is where an experiment has been repeated many times. In these cases we have learned that it is reliable to predict that when we repeat an experiment in the future, which we have done many times in the past, the probability distribution of future outcomes will be the same as observed in the past. Usually we take this to be explained by the existence of funda mental timeless laws which control all change. But this could be an over-interpretation of the evidence. What we need is only that there be a principle that measurements which repeat processes which have taken place many times in the past yield the same outcomes as were seen in the past."
Lee Smolin, https://arxiv.org/pdf/1205.3707.pdf

To be honest i dont think that Smolin managed to explain this as good as it maybe could. As i see it, you can easily misread this suggestion and find it completely ridiculous, but then think again. The idea is, could the reason for the APPARENT timeless law, that most of use think of as constraints, simply be explained as a principle where nature tends to (in a sense of induction) respond as it always did? Seen the right way, this is a rational action principle in disguise. It also is a kind of solution to the problem of induction, as we know the problem is that the induction can be flat our wrong (ie no black swans). But this might not be how nature works! Its not a matter ot true or false, its a matter of best guess. If you only have seen white swans, betting on another white swan may still be a goot bet. Sometimes the best guess is wrong, and sometimes its exactly this explains certain interactions.

You can apply this reasoing also to "symmetries" if you consider the actual observer symmetries of an observer. If a certain observer has evidence for a certain symmetry, it will itself proabably behave "as if" this was law. But it is not. And sometimes a black swan actaully appears and breaks the illusion. But nature might be a stable illusion, and how else to explain it?

This is a way to also then understand evolution of law.

Then add the ideas of evolving laws of smolin, and you arrive at my position.

/Fredrik
 
Fra
3,073
142
Do you know of authors or papers where they explored the "dna of physical law" as you put it? Where there is perhaps some idea of elementals that embody certain forces of nature... this is the truly radical theory.. smolin stuff is just not radical or powerful enough to explain all of nature.
No I don't. Given how the field looks like, i think its equally probably to find that book in shops written anyone, as it is to work this out all on your own and write it yourself.
I like the part where he mentioned:

"* the fundamental theory will not be quantum mechanical.. but quantum mechanics will emerge in the case of small subsystem.
* the fundamental theory will not exist in space, but space will be emergent in some eras of the universe."
Its exactly when you think about this that not even QM as generalized probability theory in the sense of hardy and entropic dynamics solves the problem. The problem is that these ideas solve the problem that was created when we went from classical physics to QM. And where we still have a classical observer, to "attach" probability to. The limit of small subsystems is imo related to the limit of a large classical observer. Its the same thing relationally. As long as we are in this domain, the generalized probability theory works fine.

But in cosmological theories of measurement, and when you consider the logic of unification, i think the problem is much worse. And the revolution needed here is larger than the transition from classical realism to QM, now some 100 years ago. After all, the "probability" in QM is still realistic. The "generalization" needed is much more radical i think.

Some people are still thinking the classical->quantum is a problem (which it partly is) but to the point where they dont see the next generation of the bigger problem. If one thinks quantum mechanics is "weird", the new thing we seek is going to be far harder to "grasp".

/Fredrik
 
star apple
No I don't. Given how the field looks like, i think its equally probably to find that book in shops written anyone, as it is to work this out all on your own and write it yourself.

Its exactly when you think about this that not even QM as generalized probability theory in the sense of hardy and entropic dynamics solves the problem. The problem is that these ideas solve the problem that was created when we went from classical physics to QM. And where we still have a classical observer, to "attach" probability to. The limit of small subsystems is imo related to the limit of a large classical observer. Its the same thing relationally. As long as we are in this domain, the generalized probability theory works fine.

But in cosmological theories of measurement, and when you consider the logic of unification, i think the problem is much worse. And the revolution needed here is larger than the transition from classical realism to QM, now some 100 years ago. After all, the "probability" in QM is still realistic. The "generalization" needed is much more radical i think.

Some people are still thinking the classical->quantum is a problem (which it partly is) but to the point where they dont see the next generation of the bigger problem. If one thinks quantum mechanics is "weird", the new thing we seek is going to be far harder to "grasp".

/Fredrik
Fra. I'm looking for a theory or paper where this whole spacetime/matter being emergent from something else and relational quantum mechanics and information flow thing by Rovelli and Smolin, etc. can be related to Dark Matter.. that is.. matter and dark matter being part of the fundamental theory that uses relational (or inference) measurement thing that doesn't use quantum mechanics (as mentioned by Smolin). Remember the fact of the matter is that there is no theory of dark matter consistent with all the data. So use dark matter as extension of matter in the fundamental theory that won't use quantum mechanics nor occur in space as Smolin mentioned but where space is emergent. Is this possible? Please give the fundamental ideas (or any paper) if any author has explored this before. Thanks.
 
Fra
3,073
142
There are so many of papers out there, and while its important to somehow be aware of that others have done it is a huge task on its own. All I can say is that there are no papers i have stumbled upon that is doing things that fully complies to my thinking. But as we just discussed there are many that i think partially in the right direction.

Maybe someone else can advise. Marcus that isnt with us anymore used to do a good jump by monitoring and highlightning new papers. I dont really spend any time at all screening papers, its more that i stumble upon them due to references etc.

But if we turn this around, and ask pragmatically if I had to pick one of the major programs that i think is the "least bad" with biggest potential then i would probably be string theory after all. While i think the program by design is not addressing the foundational quesitons rationally, it has at least the potential to maybe work out their problems and actually turn into a theory of inference (although i am in doubt as it needs to change so much that the "strings" would be something else), where the branes and various dual -theories correspond to different inference systems, which in turns correspond to different "observers" and the landscape is then real, and should be understood evolutionary. The missing part is to understand the evolution mechanisms withing the landscape; why are certain theories not manifest in nature while others are? I think there are no deductive answer to this, but the answer maybe lies in evolutionary learning algorithms. But if you se it this way, the original starting point of constructing string theory from quantiing a classical string is not the right way to understand it. This is just the historical path, which i consider to be accidental, providing no insight - probably just confusion! This is the reason why i still enjoy some of wittens writings, just to try to guess what new ideas that may come from there.

Just a remote hope there was this thread, but still far from the vision
https://www.physicsforums.com/threads/a-new-hope-for-st-hold-the-thought-of-jonathan-j-heckman.923630/

/Fredrik
 
star apple
There are so many of papers out there, and while its important to somehow be aware of that others have done it is a huge task on its own. All I can say is that there are no papers i have stumbled upon that is doing things that fully complies to my thinking. But as we just discussed there are many that i think partially in the right direction.

Maybe someone else can advise. Marcus that isnt with us anymore used to do a good jump by monitoring and highlightning new papers. I dont really spend any time at all screening papers, its more that i stumble upon them due to references etc.

But if we turn this around, and ask pragmatically if I had to pick one of the major programs that i think is the "least bad" with biggest potential then i would probably be string theory after all. While i think the program by design is not addressing the foundational quesitons rationally, it has at least the potential to maybe work out their problems and actually turn into a theory of inference (although i am in doubt as it needs to change so much that the "strings" would be something else), where the branes and various dual -theories correspond to different inference systems, which in turns correspond to different "observers" and the landscape is then real, and should be understood evolutionary. The missing part is to understand the evolution mechanisms withing the landscape; why are certain theories not manifest in nature while others are? I think there are no deductive answer to this, but the answer maybe lies in evolutionary learning algorithms. But if you se it this way, the original starting point of constructing string theory from quantiing a classical string is not the right way to understand it. This is just the historical path, which i consider to be accidental, providing no insight - probably just confusion! This is the reason why i still enjoy some of wittens writings, just to try to guess what new ideas that may come from there.

Just a remote hope there was this thread, but still far from the vision
https://www.physicsforums.com/threads/a-new-hope-for-st-hold-the-thought-of-jonathan-j-heckman.923630/

/Fredrik
I thought you read every paper at arxiv. Ok. Good to know you like Superstrings.. and not a hater of it like some LQG folks. i'll google everything I could read about Superstrings without SUSY and relational QM and how they combine the two. I need a good background of superstrings and will read about it (and contemplate it) for the remaining days of the year. Thanks a lot for sharing.
 
Fra
3,073
142
I thought you read every paper at arxiv.
[emoji1]

/Fredrik
 
There are so many of papers out there, and while its important to somehow be aware of that others have done it is a huge task on its own. All I can say is that there are no papers i have stumbled upon that is doing things that fully complies to my thinking. But as we just discussed there are many that i think partially in the right direction.

Maybe someone else can advise. Marcus that isnt with us anymore used to do a good jump by monitoring and highlightning new papers. I dont really spend any time at all screening papers, its more that i stumble upon them due to references etc.

But if we turn this around, and ask pragmatically if I had to pick one of the major programs that i think is the "least bad" with biggest potential then i would probably be string theory after all. While i think the program by design is not addressing the foundational quesitons rationally, it has at least the potential to maybe work out their problems and actually turn into a theory of inference (although i am in doubt as it needs to change so much that the "strings" would be something else), where the branes and various dual -theories correspond to different inference systems, which in turns correspond to different "observers" and the landscape is then real, and should be understood evolutionary. The missing part is to understand the evolution mechanisms withing the landscape; why are certain theories not manifest in nature while others are? I think there are no deductive answer to this, but the answer maybe lies in evolutionary learning algorithms. But if you se it this way, the original starting point of constructing string theory from quantiing a classical string is not the right way to understand it. This is just the historical path, which i consider to be accidental, providing no insight - probably just confusion! This is the reason why i still enjoy some of wittens writings, just to try to guess what new ideas that may come from there.

Just a remote hope there was this thread, but still far from the vision
https://www.physicsforums.com/threads/a-new-hope-for-st-hold-the-thought-of-jonathan-j-heckman.923630/

/Fredrik
There is a nice name for this problem that there are too many papers and everyone is struggling to keep up with what's happening: Research Debt. However, so far there is no good solution.
 
Jimster41
Gold Member
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Yes this is the key. I can only guess, but the probable idea that fits in string thery is bulk dimensionality is emegent from boundaries. And there new symmetries form. This need to be phrased without starting from 4d continium spacetime baggage.
The part that I got caught on is what models are there that can describe a system that starts with no symmetries (isn't this like as a non-repeating fractal?) but develops/supports symmetries?
This seems to be the implication that "symmetries are emergent": To some observer there ain't any in the raw ingredient but they show up in the pie when you mix and bake those ingredients.

I was struck by how there are fractals that are non-repeating and there are fractals that repeat periodically (have symmetric states?).
What I wondered is whether there are multi-fractals that start with more than one of the first kind (non-repeating/a-symmetric) and produce the second (repeating/supporting symmetries). It's one mathematical model that I can think of that at least maybe could support the idea of the symmetry pie with purely asymmetric ingredients- though maybe there are others.

I have this naive cartoon that strings start with symmetries - because the simplest strings themselves are symmetric (identical). So strings already require the support for symmetry.

I know this is all naive, please consider it a question.

[I am certainly confused about the difference between irrational numbers and non-repeating fractals, maybe that's obvious]
 
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