2,780 reputation
1324
bio website staff.science.uu.nl/~hooft101
location Utrecht, Netherlands
age
visits member for 2 years, 9 months
seen Jan 20 at 23:07

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.


Feb
27
revised How does Bell's theorem rule out the possibility of local hidden variables?
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Feb
27
answered How does Bell's theorem rule out the possibility of local hidden variables?
Feb
27
comment What are the 't Hooft papers about classical models underlying QM?
except that it raises the suspicion that what's really happening in this world might be just these ontological states, and the rest is due to our limited understanding, somewhat contaminated with some sort of religious feeling that God likes to superimpose. So, the answer to @Motl's objection is that it's our equations used to describe observed reality that allow for superpositions, not reality itself. I thought that this statement would be trivial and unimportant, but if not understanding it causes someone to reject the models first-hand, apparently the statement is important after all.
Feb
27
comment What are the 't Hooft papers about classical models underlying QM?
Our theory is now that physicists describing the real world have no way of knowing whether they are describing an ontological event, or just any other solution of their equations (except when it's about cats, where we think we DO know!). The simple reason for this is that Schroedinger's equation is linear. We keep that property throughout. But now I add something new: a true, ontological state should, some way or other, evolve to become again a true, ontological state. That's just a constraint on the set of Schroedinger's equations that we impose. What's wrong with that? Nothing of course,
Feb
27
comment What are the 't Hooft papers about classical models underlying QM?
There's this little point that @Motl failed to grasp about these models: It's the "ontological, true" events described here that are such that any superposition of such events is NOT an ontological event. That's just like cats: the dead cat is ontological, the live one is, but any superposition of the two isn't, or at least, that's the case in our models. Now the superposition of the two cats DOES obey Schroedinger's equation. What I have done is take all "ontological" states of a system and look at the equations they obey. Now superpositions of ontological states also obey the equations.
Dec
27
awarded  Good Answer
Nov
8
comment Will Determinism be ever possible?
sigoldberg1 and Seamus's remarks about Laplace apply if the world is described by real numbers. The problem with real numbers is that they each require infinite sets of digits. If you can't control the millionth digit you will have indeterminism. This problem would not arise if we would have theories based only on integers, or even better, bounded integers.
Nov
7
comment Will Determinism be ever possible?
Indeed, I should have stated more clearly that I mean local reality, and that this should be interpreted in a completely classical sense. But, as you say, this "reality" is not about particles with position, momentum, etc. My minority view is that there is a loophole in the arguments usually employed against local reality.
Nov
4
awarded  Citizen Patrol
Nov
4
answered Will Determinism be ever possible?
Nov
1
comment Is flying really easier on smaller scales?
Apologies to AlanSE, my comments and questions were to be directed to @miceterminator.
Nov
1
revised Is flying really easier on smaller scales?
added 6 characters in body
Oct
30
comment Is flying really easier on smaller scales?
But this is what I read on my screen, signed by your name. If you didn't mean $\sqrt{\text{diameter}}$, then what are you trying to say?
Oct
28
comment Is flying really easier on smaller scales?
@AlanSE Please explain why you write $\sqrt{\text{diameter}}$ where I would have expected $\text{diameter}^2$, assuming that strength of muscle tissue is more or less size independent. Of course, the energy produced by a muscle scales with its volume, times frequency.
Oct
28
revised Is flying really easier on smaller scales?
added 2 characters in body
Oct
27
answered Is flying really easier on smaller scales?
Sep
15
revised Why do people categorically dismiss some simple quantum models?
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Sep
12
comment Why do people categorically dismiss some simple quantum models?
In principle, yes, one should be able to construct a Bohmian field theory, but I think it would be inelegant. To my taste, Bohmian mechanics adds far too many "unobservable observables" in the form of pilot waves. This would be awful for field theories, where the pilot wave would be a field functional, or a function of infinitely many particle positions.
Sep
7
comment Why do people categorically dismiss some simple quantum models?
Think of qft as a large set of quantum harmonic oscillators, each oscillating at isolated points in space. Then assume that each oscillator shows interactions only with its direct neighbors. In qft, these are quantum interactions. To most theorists, this looks sufficiently local, no spooky signals.
Sep
7
comment Why do people categorically dismiss some simple quantum models?
@user7348: No, quantum field theory as it stands has causality built in; for that, it is sufficient to demand that all commutators vanish outside the light cone. This guarantees that no signal ever will go faster than light. So qft obeys relativity and has ordinary qm particles in its non-relativistic limit. Everything is fine, no problem with relativity, until you try to understand what the ontology is. You have to remember that spacelike correlations are fine if you can explain them in terms of intial states in the past.