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comment by b_b
b_b  ·  4593 days ago  ·  link  ·    ·  parent  ·  post: Kolmogorov Complexity, Causality And Spin
The convergence in appearance of planetary nebulae, electron probability clouds, black hole jets, etc., basically results from the fact that the electromagnetic and gravitational forces both follow inverse square laws. Is his generalized thesis that the inverse square law itself, that is so common in physics, is a result of the low pass Kolmogorov filter? And that these laws can be somehow backed out of the generalized Kolmogorov complexity that he is proposing? Admittedly, I don't have any expertise on information theory, so I'm not at all qualified to critique it, but seems like a pretty awesome idea.




alpha0  ·  4593 days ago  ·  link  ·  
Alright, so Dara says:

    [that law] has a very low kolmogorov complexity i.e. 
    few ALU operations of add and shift and multiply 
    (taylor series).
    
    So LOW kolmo complexity = 1/r^2 or any other 
    simple law
I found that interesting, and it 'fits' into his framework, but it is not clear to me why that specific relationship predominates. Intuitively, I would seek a group theoretic explanation. Back to numbers and our favorite formula. Regardless, that made me do a quick search and fished this out:

    I would like to interrupt here to make a remark. The fact that
    electrodynamics can be written in so many ways - the differential
    equations of Maxwell, various minimum principles with fields, minimum
    principles without fields, all different kinds of ways, was something
    I knew, but I have never understood. It always seems odd to me that
    the fundamental laws of physics, when discovered, can appear in so
    many different forms that are not apparently identical at first, but,
    with a little mathematical fiddling you can show the relationship. An
    example of that is the Schrödinger equation and the Heisenberg
    formulation of quantum mechanics. I don't know why this is - it
    remains a mystery, but it was something I learned from experience.
    There is always another way to say the same thing that doesn't look at
    all like the way you said it before. I don't know what the reason for
    this is. I think it is somehow a representation of the simplicity of
    nature. A thing like the inverse square law is just right to be
    represented by the solution of Poisson's equation, which, therefore,
    is a very different way to say the same thing that doesn't look at all
    like the way you said it before. I don't know what it means, that
    nature chooses these curious forms, but maybe that is a way of
    defining simplicity. Perhaps a thing is simple if you can describe it
    fully in several different ways without immediately knowing that you
    are describing the same thing. 
source
b_b  ·  4593 days ago  ·  link  ·  
Ah, I think I am beginning to see more clearly his point. So can we say that a function can be said to have low Kolmogorov complexity if an infinite series expansion (Taylor series, as your example, but I suppose any infinite series could substitute) is relatively simple and repetitive? If I am making a correct assumption here, then I can better understand his point, at least qualitatively. Most physical systems are built on sets of equations that have relatively simple infinite expansions. Take for example the steady state solutions to an arbitrary separable partial diff eq, as is common in systems whose force weakens with distance. The solutions are oscillators; sines waves, bessel functions, etc. Even in QM, we see recursion formulae that determine the stable states of the wave function, single formulae that can describe the entire set of possible states for particles in a given boundary condition. I suppose this is what is meant by low Kolmogorov complexity (or I am missing the point, which is equally--or perhaps more--likely).

There is another extension of this that comes to mind, and that is the convergence of the form of equations that describe vastly different systems (beyond inverse square laws, I mean). For example, Newtonian oscillators, in some circumstances, form solutions to population models in certain ecological systems. It seems that every time that Equation X satisfies problem 1 and (unrelated) problem 2, the complexity of the system (in a descriptive sense, anyway) has decreased.

If there is some generalized string out of which these common forms of equations can be backed, I would be speechless, stunned, but not really surprised. Maybe there is hope for a unified field theory in information theory, instead of quantum (or the wretched string theory).

alpha0  ·  4593 days ago  ·  link  ·  
I think you have it. My question remains as to why 1/r^2 'emerges' over say '1/r' which is of even lower complexity. Clearly there is a sort of structural substrate that pushes up (so to speak) while the 'low pass filter' pushes down.

    If there is some generalized string out of which these common forms of equations can be backed, I would be speechless, stunned, but not really surprised. Maybe there is hope for a unified field theory in information theory, instead of quantum (or the wretched string theory).

It has to be Number. It must be N - simple act of partitioning and counting. I'm convinced of it, but how to prove it! :(

b_b  ·  4592 days ago  ·  link  ·  
I think 1/r^2 emerges because of the geometry that has emerged. If a pulse of particles is emitted uniformly in n-dimensional space, and each travels at the same speed, then their density will fall off as 1/r^(n-1), since in 3D they cover a spherical surface (2D object of size r^2), and in 2D its a line (1D circular surface of size r). Its the geometry that's important. We should search for why our world is 3D, and not some other space, if we want to know why we have inverse square laws.
alpha0  ·  4592 days ago  ·  link  ·  
quick p.s. Did you ever read Flatland by Edwin Abbott Abbott?
b_b  ·  4592 days ago  ·  link  ·  
No. But a quick search has intrigued me. I'll put it in the queue.
alpha0  ·  4592 days ago  ·  link  ·  
    Its the geometry that's important

Agreed. But is geometry more foundational than number? (I feel like we're back in ancient Greece.) There is a very interesting tension between number and geometric form. And addressing this will drag in Cantor as well. This question has been giving headaches to the pointy head set for thousands of years.

    We should search for why our world is 3D, and not some other space, if we want to know why we have inverse square laws.

Great insight and question. I wonder if answering that is beyond our ken. I am open to the future possibility, given the root words earth-measure, of a demonstration that provides a number theoretic basis for geometry. But indeed, why would it cap at 3-D. Per ancient lore, scripture, and even recent musings of string theory, there are additional dimensions that are 'unseen'. So I would read your "We should search for why our world is 3D" as "why our perception of the world is 3D".

b_b  ·  4592 days ago  ·  link  ·  
    I would read your "We should search for why our world is 3D" as "why our perception of the world is 3D".

I actually considered writing the reply that way, but I shy away from speculation; we know the universe has at least three large dimensions (four if we count time). I would love to hear a number theoretical reason for three. I can't accept that it is arbitrary. I can generally see why we can't exist in 1 or 2D, as movement around other objects would be impossible for anything solid. But I have never been able to imagine a reason why more didn't occur. I suppose that's because we can't dream in 4D. We can imagine--and therefore reasonably reject--lower dimensions, but only math can tell us about higher ones.

alpha0  ·  4592 days ago  ·  link  ·  
Actually it is interesting you mention dreams, given that our 'normal' sense of time collapses in dreams. Dreamland is a wonderfully strange and distinct reality.
alpha0  ·  4593 days ago  ·  link  ·  
    Is his generalized thesis that the inverse square law itself, that is so common in physics, is a result of the low pass Kolmogorov filter?

I'll pass the question along, but yes, that is the general thrust of the paper.

The def. of causality was imo brilliant. Also note the remark regarding the threshold of broken symmetries is the most tantalizingly clue informing the pervasive phenomena of phi/fibonacci in natural systems I have found to date.

b_b  ·  4593 days ago  ·  link  ·  
The whole idea of convergence is an interesting one. We can see it in physics, and by extension, in biology. E.g. there are marsupial "wolves" in the fossil record that require expertise to differentiate from placental wolves, because the two creatures converged to such a high degree. These convergences are a result of creatures "solving" physical problems in their environment. So physics dictates biologic form in many cases.

Have you come across D'Arcy Thompson? He spent great effort in his career trying to generalize convergent trends in evolution based on simple mathematical models (well, as simple as he could make them). He was writing before information theory was discovered. I suspect that if physical laws are generalize-able from information theory that evolutionary trends must be, as well, given that species are forged as one possibility among seemingly infinite states. (Interestingly, I first came across Kolmogorov when studying mathematical biology; there's a strange convergence!)

alpha0  ·  4593 days ago  ·  link  ·  
I promised myself I'll work today so this (and you too mk) will have to wait until the p.m. as this is a very deep and interesting discussion that deserves attention.

(Yes. I love On Growth and Form. [arch school days and my obsession to create a morphological system for generating buildings. Remember that drawing?])