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Physics Stack Exchange users whose comments are worth studying include Lubos Motl and Ron Maimon (now at http://www.quora.com/Ron-Maimon and http://www.physicsoverflow.org/user/Ron+Maimon). Also see http://arxiv.org/abs/hep-ph/0207124 for a review of physics since the standard model.


Aug
11
comment Discreteness and Determinism in Superstrings?
So basically, I consider this work an important contribution to the cause of realism in QM, it breaks new ground there. But I don't think you'll get quantum-like nonlocality from a local CA unless there is some nonlocality in the transformation from CA grid coordinates to space-time coordinates.
Aug
11
comment Discreteness and Determinism in Superstrings?
That these papers contain CAs which are equivalent to QFTs (in the limited sense that CA evolution maps to eigenvalue evolution for certain states and observables in the QFT) is no guarantee that it will even be possible to construct a "Bell scenario" in the QFT. The May paper describes a free field theory - good luck building a "detector" with that physics! - and the July paper a type of "interacting" string theory whose potentials are still unknown. The conservative prediction is that there will be no-go theorems explaining why these models, though quantum, aren't counterexamples to Bell.
Aug
11
comment Discreteness and Determinism in Superstrings?
I have to say that I do not see how the time evolution of a locally deterministic CA can violate a Bell inequality. If you had the equivalent of an EPR experiment, where the filter orientations were controlled by pseudorandom number generators, there just shouldn't be a way to get all the right counterfactuals without cheating (by finetuning the CA initial conditions, case by case).
Aug
10
comment Discreteness and Determinism in Superstrings?
There's an opportunity for someone here: try to explicitly construct EPR states, GHZ states, etc, in the field theory described in this paper, and thereby show that it can or can't be done. But act quickly, or Gerard 't Hooft himself might get there first, once again.
Aug
6
comment “Time” by epistemic subdivision of a closed system
The problem of connecting them to the world as known in physics will remain, but that is going to require new metaphysics, such as you may find in the wild lands of "quantum mind" or "quantum brain" research, and 95% of that stuff is going to be wrong, so good luck finding the right approach.
Aug
6
comment “Time” by epistemic subdivision of a closed system
It sounds like a typically confused attempt by a physicist to explain one of the many things we know about subjectively (time, existence, colors, emotions, thoughts...). You can tell this explanation is wrong because it makes time less than completely real - it is supposed to be relative or imaginary or an artefact of method of description. If you want to understand such "subjective" things, it's best to start with phenomenology, like Husserl, which doesn't try to reduce them to anything, but only seeks to ascertain their nature...
Aug
3
comment Will the Big Rip tear black holes apart?
Anon may be favoring your second possibility, see en.wikipedia.org/wiki/Nariai_spacetime
Aug
2
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Aug
2
comment Is space unending?
The true holographic boundary is future infinity, Ron. Galaxies don't stop existing when they cross our horizon! :-)
Aug
2
comment Is space unending?
Ashwin, there is one other option and that is the "closed universe" where if you go in one direction you eventually return to where you started, but from the other direction. This is impossible according to the intuitive "Euclidean" idea of space, but it is a logically self-consistent alternative idea. However, if you have to choose between the two insanities of "it goes on forever" and "it ends with a wall and there's nothing on the other side", I would advise you to choose "it goes on forever". "Space ends at a wall" is a logically well-defined possibility but it is not well-motivated.
Aug
1
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Aug
1
comment What counts as an observer and memory states in quantum interpretations?
So how do you explain memory in infants?
Jul
29
comment Discreteness and Determinism in Superstrings?
't Hooft's theory doesn't have a wavefunction at a fundamental level, just the CA. But he's saying that the dynamics of his CA is the same as the dynamics of the beables in a particular Bell-Bohm theory. This Bell-Bohm theory is the one which can be described as a basis permutation in Hilbert space, but 't Hooft is saying that if you look at the eigenvalue dynamics induced by this permutation, it equals the CA.
Jul
27
comment Why aren't we Boltzmann brains in an infinite universe?
What @Mad scientist really wants to know is, why don't BBs dominate the counting of observers? Well, any argument that BBs dominate depends on particular physical and cosmological hypotheses. So one or more of the hypotheses is wrong, and quantum cosmology is still mostly speculation, so this is hardly surprising.
Jul
27
comment Why aren't we Boltzmann brains in an infinite universe?
"Why aren't we Boltzmann brains in an infinite universe?" Because BBs usually die or disintegrate immediately after their creation. That's how we know that this is an ultra-exponentially unlikely hypothesis...
Jul
27
comment Why aren't we Boltzmann brains in an infinite universe?
"Are they all the same brain" - no, because when you apply a diffeomorphism to move one BB to where the other one is, the other one will also be moved by the diffeomorphism to a new position. So you'll still have two of them after the move.
Jul
27
comment Discreteness and Determinism in Superstrings?
... because all the dynamics is in the wavefunction part of the ontology. Similarly, the QFT observables that 't Hooft defines in terms of his ultimate CA beables (in part 6 of 1205.4107 and part 5 of 1207.3612) are the second-order beables out of which the macroscopic world is constructed. The mysterious part is that the CA dynamics is also supposed to produce the right dynamics for measurements of all observables.
Jul
27
comment Discreteness and Determinism in Superstrings?
See prac.us.edu.pl/~ztpce/QM/Bell_beables.pdf page 8 for what I think is 't Hooft's real philosophy. In this paper Bell constructs a hidden variables theory in which there is a "basic local beable" (he uses fermion number density) out of which all space-time objects are constructed. Bell remarks that any observable capable of specifying the positions of objects at mesoscopic resolution could play the role of basic local beable. Your experiment might be measuring spin, but even if your ontology only contains position beables, it will still describe the experiment correctly...
Jul
27
comment Discreteness and Determinism in Superstrings?
+1 for the remarks about ghosts, scalars, and SUSY. But you must be wrong to say that 't Hooft wants superpositions of his ontological basis states to play any role (such as representing states of imperfect knowledge). He explicitly says, e.g. in 1112.1811 page 1, that such superpositions do not occur...
Jul
25
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