2,299 reputation
1122
bio website staff.science.uu.nl/~hooft101
location Utrecht, Netherlands
age
visits member for 1 year, 8 months
seen Feb 4 at 15:15

Theoretical physicist, Utrecht University.

University Professor. Elementary particle physics, quantum gravity, black holes, quantum mechanics.

Won some prizes (such as the nobel prize 1999), but please don't hold that against me.


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revised Why do people categorically dismiss some simple quantum models?
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revised Why do people categorically dismiss some simple quantum models?
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Aug
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answered In 't Hooft beable models, do measurements keep states classical?
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comment In 't Hooft beable models, do measurements keep states classical?
Let me add a question, for comparison: My favorite "classical" theory is the planetary system, assuming that planets move as point particles under Newton's laws. Yoy can actually introduce non-commuting operators there as well. The "Earth-Mars exchange operator" puts Mars where Earth is and Earth where Mars is (and some simple rules about their velocities and moons). The eigenvalues of this operator are $\pm 1$. We can calculate how it evolves. Is this an observable?
Aug
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awarded  Popular Question
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awarded  Revival
Aug
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answered Discreteness of Spacetime and Violation of Lorentz symmetry
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awarded  Supporter
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Aug
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comment Why do people categorically dismiss some simple quantum models?
@Peter Shor: I have always opted for your 3rd possibility: the "error correcting codes" will eventually fail. The quantum computer will not work perfectly (It will be beaten by a classical computer, but only if the latter would be scaled to Planckian dimensions). This certainly has not yet been contradicted by experiment.
Aug
17
comment Why do people categorically dismiss some simple quantum models?
@ Lubos Motl, you still didn't get it: the ammonia molecule is in the SM, and there superpositions are meaningful. But if you use the CA as a basis, superposition of two basis elements acts as a classical composition with classical probabilities. "Superdeterminism" here boils down to saying that 2 ammonia states that are not orthogonal only become "ontic" if you make them orthogonal by including other quantum states elsewhere, and making those orthogonal. It looks inelegant but I do think that this actually happens.
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answered Why do people categorically dismiss some simple quantum models?
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comment Why do people categorically dismiss some simple quantum models?
To be precise: the ontic states are only separable if presented with the CA states as basis. The states are non-separable if described with Standard Model(SM) states as a basis. The SM states obey local diff equs when expressed in terms of CA states, but the solutions of these equations are non-local.
Aug
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comment Why do people categorically dismiss some simple quantum models?
-| the upsetting thing is that this might not be true. The ontic states of the universe may form a much smaller class of states psi_i -| all we need to assume is that all ontic states of the universe form an orthonormal set. This orthonormal set is NOT separable, and this is why, locally, we think we have not only the basis elements but also all superpositions. Observe that it is easy to imagine such sets. This orthonormal set is then easy to map onto an automaton. There is no need to think that this automaton cannot be a local one.
Aug
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comment Why do people categorically dismiss some simple quantum models?
I am tempted to think that the answer to this question is a radical one, that may well upset many of you: -| to describe our world, we have invented Hilbert space which contains not only basis elements but also all superpositions. -| we have learned to think that this Hilbert space is separable, that is, inside every infinitesimal volue element of this world there is such a Hilbert space, and the entire Hibert space is the product of all these. -| normally, we assume that any of the states in this joint Hilbert space may represent an "ontic" state of the Universe.
Aug
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comment Why do people categorically dismiss some simple quantum models?
The real issue I think has been exposed most clearly by Ron Maimon and some others in their earlier contributions: the problem is that in a CA the "ontic" wave function of the universe can only be in specific modes of the CA. This means that the universe can only be in states psi_1, psi_2, ... that have the preoperty ( psi_i | psi_j ) = delta_ij (apologies for this non-latex notation), whereas the quantum world that we would like to describe allow for many more states that are not at all orthonormal to each other. How could these states ever arise?
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