Dear Stefan,
For some reason, Lawrence Crowell cannot post on the FQXi and has not been able to do so for several days. FQXi is fixing the problem. In the meantime, Lawrence asked me to post here his comments on your Essay. I past them below. I profit by this email to inform you that I will also read comment and score your Essay soon.
Good luck in the Contest and best wishes,
Ch.
From Lawrence Crowell
This is a bit late, for some reason I can't post to FQXi. I meant to post this several days ago.
I just read your informal essay and there are points I agree with. Thanks for the kind words with respect to my essay. I finally just now got to reading yours, as this illness came roaring back yesterday and I am still feeling not too well. I am coming up on a month with this thing. I have not been horribly ill, but it is rather debilitating and leads to deep levels of fatigue.
You are making issues with what I see as the continuum. The continuum hypothesis Чђ_0 < C < 2^{Чђ_0} is something that haunts all of this. I am not an expert on this, though I have Cohen's book on the proof he worked on that it is consistent with ZF set theory, but not provable. From a physics perspective it seems almost absurd to worry about this. Though with Robinson's numbers and related matters this does impact the ideas behind calculus. With large N entanglements of states a continuum though should exist. The Raamsdonk idea that spacetime is an epiphenomenology of quantum entanglement should imply that a smooth continuum will emerge from a finite, or with N в†'П‰,using ordinal notation instead of в€ћ, discrete system of states. This can never be observed completely with physics, but it would give a theoretical reason to think there are no granular disruptions to spacetime, at least for IR (E в†' 0) measurements such as across cosmological distances. The NASA and ESA Fermi and Integral measurements bear this out. At UV measurements spacetime should I think appear very bubbly or granular with discreteness, where what are measured are just discrete states and not even what we could call space or spacetime.
You wrote, "Hence, our axiom that the world is an informationally closed (void) system must be erroneous, since the fact that GГ¶del-incompleteness is factually constructible contradicts this axiom." This is a part of what I advocate on several fronts. A black hole with mass m = GM/c^2 has a temperature T = 1/8ПЂm in natural units. If this black hole were placed in a spacetime region with a background temperature equal to its Bekenstein temperature the black hole will emit and absorb photons in a stochastic way. This will mean the temperature and mass of the black hole will drift away from this condition of equality in a Langevin manner. The result is there is no equilibrium. This then points to an open world perspective instead of a closed world.
The halting issue also impact spacetime. Suppose there is a binary state on a Turing machine that we read out. We set this machine to make its first step in 1 second, the next in ВЅ of a second, the next in Вј of a second, it is not hard to see that after 2 seconds we should have an answer. If this machine halts it will finish before 2 seconds. If not something odd happens, for the energy required to fun this machine diverges in an asymptote and even it if is "unbreakable" the energy involved will generate a black hole. If this machine does not halt, we have a black hole, and even if it halts but takes a huge amount of time it could be in a black hole. Thus, if we generate a black hole, we have no information about the halting state of the machine. We must go into the black hole to find out. A Kerr black hole has an inner event horizon, and we could instead have the Turing machine send a regular interval of binary pulses into the black hole. An observer who goes into the black hole could then in principle read off this binary stream and determine completely if a black hole halts or does not halt. This is because the inner horizon is continuous with I^в€ћ and the infalling observer would reach this in a finite time in an eternal black hole. However, the Planck unit of distance muddles this up, and further Hawking radiation breaks the connection between r_- and I^в€ћ. In fact, as the observer reaches r_- it is a singularity at the end point in the black hole explosion into Hawking radiation. So, either spacetime physics or quantum mechanics enforces a condition whereby the GГ¶del-Turing result can't be overruled by physical means.
These are interesting matters to ponder and think about. Your essay does provide food for thought along these lines.
Cheers LC