Quantum mechanics has a “branch both ways” that is sometimes mistaken for randomness. True randomness would be non-unitary and break a bunch of the maths.
Which is an odd things to say, since the maths used by Copenhagenists is identical to the maths used by many worlders.
It isn’t totally inconceivable that the universe does it anyway, but it seems unlikely. Do you have any coherent idea of what the universe might possibly do
You are trying to appeal to the Yudkowsky version of Deutsch as incontrovertible fact, and it isn’t.
If the MWI is so good, why do half of all physicists reject it?
If Everett’s 1957 thesis solved everything, why have there been decades of subsequent work?
Bearing in mind that evolution under the Schrodinger equation cannot turn a coherent state into an incoherent one, what is the mechanism of decoherence?
What is there a basis problem, and what solves it?
If the MWI is so good, why do half of all physicists reject it?
Because physisists aren’t trained in advanced rationality, program length occams razor etc. Their professor taught Copenhagen. And many worlds is badly named, misunderstood and counterintuitive. The argument from majority can keep everyone stuck at a bad equilibrium.
If Everett’s 1957 thesis solved everything, why have there been decades of subsequent work?
If the sentence “god doesn’t exist” solved theology, why is there so much subsequent work.
Bearing in mind that evolution under the Schrodinger equation cannot turn a coherent state into an incoherent one, what is the mechanism of decoherence?
I don’t think there is one. I think it likely that the universe started in a coherent state, and it still is coherent.
Note a subtlety. Suppose you have 2 systems, A and B. And they are entangled. As a whole, the system is coherent. But if you loose A somewhere, and just look at B, then the maths to describe B is that of an incoherent state. Incoherence = entanglement with something else. If a particle in an experiment becomes incoherent, it’s actually entangled somehow with a bit of the measuring apparatus. There is no mathematical difference between the two unless you track down which particular atom in the measuring apparatus.
I don’t think there is one. I think it likely that the universe started in a coherent state, and it still is coherent
Then why don’t we see other universes, and why do we make only classical observations? Of course, these are the two problems with Everett’s original theory that prompted all the subsequent research. Coherent states continue to interact, so you need decoherence for causally separate, non interacting worlds...and you need to explain the preponderance of the classical basis, the basis problem.
Incoherence = entanglement with something else.
No, rather the reverse. It’s when off diagonal elements are zero or negligible.
Decoherence, the disappearance of a coherent superposed state, seems to occur when a particle interacts with macroscopiic apparatus or the environment. But thats also the evidence for collapse. You can’t tell directly that you’re dealing with decoherent splitting,rather than collapse because you can’t observe decoherent worlds.
Then why don’t we see other universes, and why do we make only classical observations?
What do you mean by this. What are you expecting to be able to do here?
Shrodingers cat. Cat is in a superposition of alive and dead. Scientist opens box. Scientist is in superposition of feeding live cat and burying dead cat.
The only way to detect a superposition is through interference. This requires the 2 superimposed states to overlap their wavefunction. In other words, it requires every last particle to go into the same position in both worlds. So it’s undetectable unless you can rearrange a whole cat to atomic precision.
Coherent states continue to interact, so you need decoherence for causally separate, non interacting worlds.
In practice, if two states are wildly different, the interaction term is small. With precise physics equipment, you can make this larger, making 2 states where a bacteria is in different positions and then getting those to interact. Basically, blobs of amplitude need to run into each other to interact. Quantum space is very spacious indeed, so the blobs usually go their own separate way once they are separated. It’s very unlikely they run into each other at random, but a deliberate collision can be arranged.
No, rather the reverse. It’s when off diagonal elements are zero or negligible.
That is what the matrix looks like, yes.
But thats also the evidence for collapse.
Interaction with the environment is a straightforward application of schrodingers equation. Collapse is a new unneeded hypothesis that also happens to break things like invarence of reference frame.
Show that coherence is simple but inadequate, and decoherence is adequate but not simple
.
Shrodingers cat. Cat is in a superposition of alive and dead. Scientist opens box. Scientist is in superposition of feeding live cat and burying dead cat.
The two problems with this account are 1) “alive” and “dead” are classical states—a classical basis is assumed. and 2) the two states of the observer are assumed to be non-interacting and unaware of each other. But quantum mechanics itself gives no reason to suppose that will be the case. In both cases, it needs to be shown, and not just assumed that normality—perceptions “as if” of a single classical world by all observers—is restored.
So it’s undetectable unless you can rearrange a whole cat to atomic precision.
So you can’t have coherent superpositions of macroscopic objects. So you need decoherence. And you need it to be simple, so that it is still a “slam dunk”.
Basically, blobs of amplitude need to run into each other to interact.
How narrow a quantum state is depends, like everything, on the choice of basis. What is sharply peaked in position space is spread out in frequency/momentum space.
Interaction with the environment is a straightforward application of schrodingers equation.
No it isn’t. That’s why people are still publishing papers on it.
Which is an odd things to say, since the maths used by Copenhagenists is identical to the maths used by many worlders.
You are trying to appeal to the Yudkowsky version of Deutsch as incontrovertible fact, and it isn’t.
If the MWI is so good, why do half of all physicists reject it?
If Everett’s 1957 thesis solved everything, why have there been decades of subsequent work?
Bearing in mind that evolution under the Schrodinger equation cannot turn a coherent state into an incoherent one, what is the mechanism of decoherence?
What is there a basis problem, and what solves it?
Because physisists aren’t trained in advanced rationality, program length occams razor etc. Their professor taught Copenhagen. And many worlds is badly named, misunderstood and counterintuitive. The argument from majority can keep everyone stuck at a bad equilibrium.
If the sentence “god doesn’t exist” solved theology, why is there so much subsequent work.
I don’t think there is one. I think it likely that the universe started in a coherent state, and it still is coherent.
Note a subtlety. Suppose you have 2 systems, A and B. And they are entangled. As a whole, the system is coherent. But if you loose A somewhere, and just look at B, then the maths to describe B is that of an incoherent state. Incoherence = entanglement with something else. If a particle in an experiment becomes incoherent, it’s actually entangled somehow with a bit of the measuring apparatus. There is no mathematical difference between the two unless you track down which particular atom in the measuring apparatus.
Then why don’t we see other universes, and why do we make only classical observations? Of course, these are the two problems with Everett’s original theory that prompted all the subsequent research. Coherent states continue to interact, so you need decoherence for causally separate, non interacting worlds...and you need to explain the preponderance of the classical basis, the basis problem.
No, rather the reverse. It’s when off diagonal elements are zero or negligible.
Decoherence, the disappearance of a coherent superposed state, seems to occur when a particle interacts with macroscopiic apparatus or the environment. But thats also the evidence for collapse. You can’t tell directly that you’re dealing with decoherent splitting,rather than collapse because you can’t observe decoherent worlds.
What do you mean by this. What are you expecting to be able to do here?
Shrodingers cat. Cat is in a superposition of alive and dead. Scientist opens box. Scientist is in superposition of feeding live cat and burying dead cat.
The only way to detect a superposition is through interference. This requires the 2 superimposed states to overlap their wavefunction. In other words, it requires every last particle to go into the same position in both worlds. So it’s undetectable unless you can rearrange a whole cat to atomic precision.
In practice, if two states are wildly different, the interaction term is small. With precise physics equipment, you can make this larger, making 2 states where a bacteria is in different positions and then getting those to interact. Basically, blobs of amplitude need to run into each other to interact. Quantum space is very spacious indeed, so the blobs usually go their own separate way once they are separated. It’s very unlikely they run into each other at random, but a deliberate collision can be arranged.
That is what the matrix looks like, yes.
Interaction with the environment is a straightforward application of schrodingers equation. Collapse is a new unneeded hypothesis that also happens to break things like invarence of reference frame.
Show that coherence is simple but inadequate, and decoherence is adequate but not simple .
The two problems with this account are 1) “alive” and “dead” are classical states—a classical basis is assumed. and 2) the two states of the observer are assumed to be non-interacting and unaware of each other. But quantum mechanics itself gives no reason to suppose that will be the case. In both cases, it needs to be shown, and not just assumed that normality—perceptions “as if” of a single classical world by all observers—is restored.
So you can’t have coherent superpositions of macroscopic objects. So you need decoherence. And you need it to be simple, so that it is still a “slam dunk”.
How narrow a quantum state is depends, like everything, on the choice of basis. What is sharply peaked in position space is spread out in frequency/momentum space.
No it isn’t. That’s why people are still publishing papers on it.