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  • Post #54

Dear Tommaso

After recovering from my cataract operations I re-read your essay, and enjoyed the lovely photo of the pomegranate and the beautiful causal set plots. I also read the paper by Reid that you referred to. I still do not understand several aspects of causal sets. With my limited understanding of the technicalities involved I will try to express my reaction to the concept as applied to physics: You started by discussing automata and I could follow the logic of causality between nodes following a simple algorithm as in Wolfram's NKS. I have no access to the printed references of your other papers and could not understand the Termite simulations.

Generally I think complications occur when applying the automata concept to physics. GR and Quantum mechanics are accepted as they are now formulated, and the simplicity of a node structure has to be abandoned to accommodate their physically unrealistic and mutually incongruous methodologies. The resulting causal sets are bloated beyond necessity. In my earlier 2005 Beautiful Universe theory on which my present fqxi paper is based, both GR and QM have to be reverse-engineered and some complications discarded before my simple dielectric node-interactions are applied. Hope this makes some sort of sense!

Best wishes from Vladimir

At that level, a universal computation keeps running. We do not know yet

the program code, but, in accordance with a fundamental principle of minimality

('Occam razor'), we like to believe that it is small, at least initially.

Tommaso,

Do you think we will ever know the "program code"? You provide a fetching argument, but I tend to believe that reality is unknowable, though my argument isn't as definitive as yours.

Jim Hoover

    Hi Juan Enrique,

    first let me clarify once more that the computational model I regard as most promising for deriving causal sets (that is, instances of spacetime) is NOT cellular automata, but network mobile automata, a sort of Turing machine acting on graphs by applying graph rewrite rules. In the causal sets derived from the computations of this model, MANY 'particles' may emerge as a result of the operation of ONE single, state-less control head, as it happens with Turmites. With cellular automata you may also obtain many particles, but you have to assume the synchronous action of MANY cells (many active elements). One active element is cheaper than many.

    It seems that the ingredients you require for cooking your universe are MANY particles, modeled as some sort of relatively complex automata. It would be interesting to run some simulation of your system, for checking what might possibly emerge. Being very lucky, this might give some anticipation of what could happen when starting with more minimalistic assumptions.

    But, for interacting, your automata probably need a background where to move. That's additional work to be carried out, and another elements that adds 'weight' to the model...

    Cheers

    Tommaso

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    • Post #57

    Constantin,

    your last post is basically a cut and paste of your original message: I could probably cut and paste my original answer again here (but I won't). Apparently, none of my arguments has succeeded in convincing you that there are many good reasons for investigating the computational universe conjecture (not 'theory'), in spite of the many problems that are still open. Never mind. I still see the glass half-full, while you see it half-empty...

    Tommaso

    PS - When you cross a black-hole horizon, nothing special happens to you; hitting the singularity at its center is another story. But in a discrete model of spacetime there is no room for infinities, and we talk, for example, of huge, but still finite curvature. A computation may well produce (or take place on) a graph with huge curvature!

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    • Post #58

    Thanks on the comments. Very enlightening.

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    • Post #59

    Yes, my last post is basically a cut and paste of my original message because I don't received any rational answer. Your ''answer'' explains nothing, it is a stream of senseless information; I'm afraid it is impossible to find an answer because it is a fundamental flaw in this theory.

    ''I could probably cut and paste my original answer again here.'' It makes no sense to cut and paste it, since it is a senseless information. Your ''original answer'' cannot explain my questions and therefore it is senseless.

    ''But in a discrete model of spacetime there is no room for infinities, and we talk, for example, of huge, but still finite curvature''.

    Please read Wikipedia Black Hole - ''At the center of a black hole lies a gravitational singularity, a region where the spacetime curvature becomes infinite. Inside of Black Hole the exchange of information is not possible, consequently no computation is possible. Since I found at least one phenomenon that exist without need in computation conjecture, it is a proof this theory/essay is wrong.

    Also this theory is forbidden by quantum mechanics and Heisenberg Uncertainty. The computational conjecture is not able to explain the motion of a simple particle and Heisenberg Uncertainty. To process the motion of particle, your computation conjecture must know the complete information about position and momentum before events occurs. Also I found other errors yet in this theory.

    ''there are many good reasons for investigating the computational universe conjecture''

    We need the true, powerful Science, if we support the erroneous theories our civilization may die. There are revolutionary theories supported by nobody because all money are absorbed by false theories. It is a crime against humanity and science to support the false theories.

    Constantin

    Hi James,

    I am certainly optimistic about the possibility for science to understand more and more about nature, but I can imagine at least one way in which this process will never come to a conclusion. The upper end of the hierarchy of natural emergence is a moving target, that science cannot anticipate, but only monitor. I believe that science will never be able to predict the major evolutionary steps in the history of the universe, or the next layer of emergence (a simple retrospective example of such a step would be the appearance of life as we know today). The reason is that simulating this evolution would take at least as much time as the time taken by nature for unfolding it for real. There is no computational shortcut. In this respect, Wolfram had the right intuition with his concept of 'computational irreducibility'.

    Nevertheless, I expect a number of nice progresses to happen, as we try to figure out the 'program code' for nature. To me, one of the most desirable achievement is as follows. We should be able to find a simple program in which the localized entities that emerge should not only be capable of Turing-universal interactions (this has been done), but should also manifest some ability to modify their own behavior, to compete, and to evolve, giving rise to a sort of Darwinian ecology. I am fully convinced that the mechanisms of natural selection and evolution should play a role also at the level of physics, not only of biology. Perhaps a first indication of this trend would be the emergence of a population of entities that act as sequential (in the sense of stateful), as opposed to combinatorial (stateless) devices. Note that this whole system should be fully supported by the operation of ONE control head only. And, we should not explicitly program the system for behaving like that -- it should all emerge for free. This is what I believe is possible, and has NOT been done yet!

    As I suggest at the beginning of my essay, it would also be great if the rule of operation of this little automaton were not fixed apriori, but evolved itself...

    Dear Tommaso

    I read your essay with great interest, I think the possibility of model reality based on a digital model is a very interesting point but the potentiality it does not reside on the discreteness but on emergence. I tried to explain this on my essay from a different perspective that reveal the importance or true meaning of the digital approach, I would like to hear your opinions about it.

    Regards,

    J. Benavides

      Hi John,

      I've read your essay and I really like it. I will rate it, and comment at your page. Ciao

      Tommaso

      P.S. Fotini Markopoulou is a 'she', not 'he'.

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      • Post #63

      Hello,

      I liked this essay. I think it is more appropriate for this contest although I think it considers a very restrictive view of the problem. Unlike the other three essays of high popularity, which I basically believe they should not have been accepted at all, this essay offers a novel perspective although too "ontological".

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        • Post #64

        Peter, I think your comment is mean and uninformed. You should be reminded to be constructive. Remember that the essays are being rated by the community too, so if you think they don't even deserve to be accepted you are also disqualifying the rest of the participants.

        Thank you Peter.

        I guess that any unifying theory of everything, and, in particular, one based on emergence, will be somehow 'restrictive' by definition: it will consist of a simple, completely abstract-looking, computational rule, and all the rest should emerge from there. Proving that the right physics eventually emerges will require a lot of additional brain and computer work, but that would not be, strictly speaking, part of the fundamental theory. Anyway, I suspect this is not what you meant by 'restrictive' -- or was it?

        As for the 'ontological' flavor, in fact I am doing a lot of concrete things in my daily research on this topic, as reported in some of the references. Mainly, I am designing and implementing algorithms, turning computations into causal sets (spacetime candidates), monitoring their behaviors by devising appropriate complexity indicators, and so on. Several essays in this contest seem to follow much more philosophical paths.

        Thanks a lot for considering my essay well organized. At this point, however, I have clearly identified a presentation bug: I should NOT have included Figure 2 ('Emergent structures in Wolfram's elementary cellular automaton 110'), since it apparently leads readers to erroneously believe that my work is focusing on CA's. Most of my experimental results (as discussed in some of the references) refer to automata with a single control head operating on a graph; these are much more similar to Turing machines than to CAs, and do not require global synchronization.

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        • Post #68

        Dear Tommasso

        You do not pay attention to my essay

        http://www.fqxi.org/community/forum/topic/946

          OK, perhaps I should not have said 'CAs' but rather 'automata or 'digital computation.' All in the spirit of Turing and von Neumann, at any rate!

          Best wishes,

          Paul

          Tommasso

          Very nicely written and argued essay, though I note no falsifiability. There are however possible distant parallels with my own, adding one more dynamic dimension, although I believe I show quite conclusively and falsifiably that Lorentz cannot and will not emerge from your pomegranate. I believe this also becomes intuitive. I do however see your essay as more 'on subject' than some.

          I know we are close and wish to say I think our concepts are closer than appeared initially the case. I go, and cannot go, beyond the logic and conception, that is my domain but hope you also see both aspects are important. To progress the disparity of mankind needs to work in complementarity not just in competition.

          I have just added a logical explanation in my string of where it appears our predecessors got lost over 100 years ago. It is important this is studied and analysed and I hope you will offer comment. If correct it would be nice if we could see it in use before 2020! I have offered other thought experiments in my and other strings, and could do more. If you have a test for the model do ask.

          Well written, and very best of luck

          Peter

          Tommaso

          A very interesting essay; definitely one of the more worthy approaches amongst the submissions I have had the time to look through so far.

          Has also been very interesting to see in recent times (e.g. from your paper, the discussion here and other related research) that concrete examples of work, concerned with such discrete worldview topics, are now being pursued!

          I have spent many years pondering such topics, but have not yet properly delved into fully quantitative modelling; so I will have to look into some of the work you mention or reference here.

          From your paper (and this discussion thread) I get the impression we probably have fairly similar views concerning some of the likely underpinnings of macroscopic reality

          e.g. the existence of some level of discrete substrate underlying space-time; several levels of emergent order between that substrate's operation (whatever form it is eventually found to have!) and the world we and our instruments actually observe; and some general organising principle possibly accounting for the generation of those differing levels of order/complexity (perhaps an evolutionary/Darwinian-selection type process of some sort??).

          I only heard about the contest recently, so was regrettably unable to enter an essay of my own, but if I had been able to enter, my contribution probably would have touched on some of the overall topics your essay addresses.

          So, good luck with the contest.

          Regards,

          David C.

            Hi Tommaso,

            I like your essay, well written and illustrated, and very convincing while still open to other point of view. My own work is in the way of debugging it. But I prefer to use the word hacking. I present a trivalent graph model where GR emerges through Tetrad gravitationnal field as in LQG, and where SM emerges from internal structure as E8 roots from a double D4 lattice. Surprisingly, the emergent structure in my figure 10a (48 valent supernode as a trivalent graph) is very similar to the graph on figure 23 of your paper in Complex System that I am referencing, but I haven't noticed this before. So your c(4, {16, 4}, 199) trinet may represent a fundamental cell of universe before crystallization and polarization. After this phase transition to hyperdiamond universe, spacetime would be born, instead of needing a big bang. (just a big freeze). But this universe, if perfectly crystallographic, would be perfectly void. And some minimal imperfections, yes, bugs, are nothing else that all matter, energy and forces, we have in our universe. I prefer not to remove all the bugs...

            Best regards,

            Ray

              Paul,

              sure you are right, that's the general spirit of the approach, which is in itself already quite controversial.

              But let me take this opportunity to point out that, within this general approach, several models are available that, in my opinion, should not be considered as equivalent, and not only because of the mentioned issue of global synchonization. I am referring to what Ed Fredkin calls 'the tyranny of computational universality': many models of computation are universal, that is, they can simulate a universal Turing machine and perform any algorithm. So, why bother choosing one in particular, for the foundations of physics?

              Well, when model B tries to simulate a computation of model A by using its own mode of operation, it usually needs to perform additional 'spurious' steps, that have to be filtered away in order to retain just the original steps (not to mention the fact that the original input has to be coded before being fed into the simulator). Fredkin suggests that there should be a one-to-one correspondence between the 'states and function' of the model and those observed in the physical universe: so, the choice of a specific (universal) model is indeed relevant, because we would select one, or the one, whose features have a clear physical counterpart, and viceversa.

              In my work I have adopted this nice, economical idea by Fredkin, specializing it to a one-to-one correspondence between the events of physical specetime and those of a causal set from a formal computation. And, again, the choice among different causal sets from different models is far from being irrelevant: for example, some causal sets end up being totally ordered, or admit nodes with unbounded degree, others don't. These properties have clearly an impact on the emergent physics.

              Regards

              Tommaso