51–60 of 170 posts
Sounds more like a cop-out
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So when does decoherence happen? Provide a formula for it. That is what people struggle with in quantum mechanics, MWI just deflects the question. Without a formula for when this phenomena happens any "interpretation" is just nonsense, except as a tool to get towards that formula.
There's no yes/no equation as decoherence is statistical in nature.
This is the problem with MWI gospel, people come and say that it solves all the math but it leaves gaping holes like this. And you didn't even solve the randomness, since as you say it is "statistical", although that is just a theory we currently have no formula for this.
Calling it a wave function collapse is much more honest since it accurately describes the situation, that we have no clue at what it is, why or when it happens. All we know how to do is calculate what possibly happens when we know that a wave function collapse will happen in a certain way.
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So you’re endorsing Many Worlds with an appeal to the anthropic principle. That’s fine, but you do have to assume MWI is the true interpretation of the mathematical formalism.
The Many-Worlds Interpretation is not really an interpretation. It just says that the known laws of Quantum Mechanics are correct, and that any measurement process itself has to obey the laws of Quantum Mechanics. In other words, nothing un-Quantum-Mechanical happens during measurement.
The article misses that we do not know how classical world that we perceive arises. Ultimately according to QM the whole universe is just single wave function with no probabilities. But this contradicts our experience of the classical world including that we measure probabilities. So we need to explain that to avoid various very ad-hock notions of classical measurement device and similar routes. There are attempts to…
In any case, none of the crutches of the article seem contradictory to me.
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MVI doesn't solve wave function collapses, if it did it would be able to tell exactly when the universe will split into many worlds, but it can't. So it doesn't solve anything, the difficulty with the theory is still there.
There isn't some physical event in MWI that splits worlds. It's just a consequence of decoherence.
Why that’s Feynman’s interpretation. “Shut up and calculate”
My difficulty with quantum mechanics is much earlier, that is, more elementary and basic than what Aaronson considers. I've watched MIT lectures, looked into books by experts, ..., and I get nothing I can believe in. Right in the first hour, I get questions with no answers. E.g.,
(1) Wave Function. Okay. I can't find a definition of a wave function. Nothing subtle but just the most elementary objection possible: What are the range and domain of the function? That is, for a function f, we usually write
f: A --> B
for sets A and B meaning that for each element x in set A there is an element y in set B so that f(x) = y. For function f, set A is the domain and set B is the range. Fine. Now for a wave function, what are the sets A and B? No joke -- I can't find a clean, clear, unambiguous, simple, beginning, first step definition.
(2) Everything. There is a common statement that the wave function has everything we can know about the particle, molecule, whatever. Okay: What about Schrödinger's Cat -- where in the wave function is the color of the cat? Simpler, for an electron, where in the wave function is the spin of the electron?
(3) Probability Density. We are supposed to take the complex valued wave function, take its absolute value, scale the function so that its integral is 1, and then, presto, bingo, since it is continuous, non-negative, and integrates to 1, it can be a probability density. In particular it can be the probability density of the current location of the particle. Okay, it CAN be.
Now, what is the evidence that it actually IS the probability density of the particle? That is, so far I can't find any argument, justification, reason to conclude that the probability density of the particle is not something else. E.g., the probability density of the particle might be Gaussian.
(4) Hilbert Space. I've read so many times, more than I can count, that the set of all wave functions form a Hilbert space. Tilt. The definition of Hilbert space I saw in math, e.g., W. Rudin, Real and Complex Analysis, is that a Hilbert space is a complete inner product space where complete means that every Cauchy convergent sequence converges. Well, the wave functions have to be differentiable and, thus, continuous, and it's easy enough to have a sequence of such functions converge to a discontinuous and, thus, not differentiable function and not a wave function. So, wave functions might be points in a Hilbert space, but they can't form a Hilbert space.
(5) Superposition. Some definitions say that superposition is just linearity. But if I have complex numbers a and b and wave functions f and g and form the linear combination
h = af + bg
that seems to be an example of superposition. Okay.
Now, is h actually also a wave function? Its absolute value might not integrate to 1. Okay, scale it so that we do get 1. Now what particle has wave function h? That is, what physics does this linear combination describe? What does h in
h = af + bg
have to do with physics? E.g., from the Pauli exclusion principle, maybe h can't correspond to anything in physics. What is going on with superposition?
(6) Can't Know. We are told that as an electron goes by, we can't know anything about it except its wave function unless we take a measurement at which time we change the wave function, what the electron might do, or some such.
Hmm. The electron has a negative charge and mass. As it goes by, it has to emit from its electric charge an electrostatic force, that is, a Coulomb field and since it has mass, a gravitational wave.
If that situation is not strong enough, then have the electron go past a strong Coulomb field so that it moves in a curve. Such a curve is acceleration so that the electron might generate a photon. We detect the photon and then "know" that the electron went by. And, even if we don't have a strong Coulomb field, our universe is awash in Coulomb fields that might deflect the electron. So, the wave function can't be "destroyed" merely by some Coulomb field. Then we just use a strong Coulomb field, detect the photon, and, thus, know a lot about the electron without changing its wave function. So, the claim that we can't know seems wrong.
(7) The Other Half. We take a beam splitter, such as in the Mach-Zehnder interferometer, and shoot an electron at it. The wave function splits into two parts, say, f and g. For part f, we have a detector. For the last electron we shot, we got a detection from part f. Now, what happens to part g?
No fair saying that part g does not exist since the Mach-Zehnder interferometer can bring such f and g back together and generate interference fringes that part f or g can't generate alone. So, part g does exist. So, what happens to it?
(8) Domain. For the wave function, a guess at the domain is the set of all ordered pairs (x, t) where x is a point in three space and t is time. Well, three space is a big place, and we usually believe that nothing can travel, propagate faster than the speed of light. So, all the wave functions so far are still traveling, still expanding. Right? What happens to them?
Just a few, simple, obvious, elementary, first day questions. I can't find any answers.
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> Plus, it can certainly have psychological implications, dramatically impacting how we feel about the things that have happened to us and life in general. Other than offering amusement by recreationally asking how many parallel universes can dance on the head of a pin, how should it affect anything? It is no mercy to know there are kinder universes out there, for with them come those more cruel. You are already a mo…
Well, do you think there is a truth, understandable by humans, about the nature of the universe? If you think there is, what better guide than our best theories of physics so far? So of course what the nature of the universe is doesn't really affect anything, on a physical level, but our sense of what happens after we're gone does in fact change our behaviors. E.g. Most people contemplate with more horror the possibi…
The Alter where you both exist and is better is not actually guaranteed to exist. In fact basically all them are guaranteed to essentially identical. Quantum splits at a macro level would basically only happen now that we have quantum random number generators to make decisions based on and I doubt that will add up to alters where things are much better.
Earlier quoted context omitted.
There isn't some physical event in MWI that splits worlds. It's just a consequence of decoherence.
But we only observe the cat being alive or dead. Where is the other cat? Are the many worlds hiding in the equation?