Multiverse theory -- Why don't strange things happen here sometimes?

[Motore]

An that's just by an additional assumption of the MWI proponents?

I am not sure if it's an asumption, it just follows from unitarity of the wavefunction. I am no expert so for details you should really take a look at an MWI paper (if you are interested).

 

[vanhees71]

That would be interesting. Do you know a paper, where this is demonstrated using unitary time evolution?

 

[Motore]

Not off the top of my head, but is should be in most of the papers about MWI. This is one thing the MWI is known for, to preserve the unitary time evolution (eg. no collapse).

 

[rolnor]

One thing, the physical world, such that we experince, is often about chemistry. Our thoghts are managed by synapses and transmittor substanses. these processes are not affected by waht spin a certain carbon atom in dopamine has? Or what spin an electron in a orbital in that atom has? So how does the quantum processes really change anything in the physical world?

 

[Motore]

Our thoghts are managed by synapses and transmittor substanses. these processes are not affected by waht spin a certain carbon atom in dopamine has?

No. In my opinion to explain any bilogical proccess you don't need QM.

So how does the quantum processes really change anything in the physical world?

https://en.wikipedia.org/wiki/Applications_of_quantum_mechanics

 

[rolnor]

No. In my opinion to explain any bilogical proccess you don't need QM.https://en.wikipedia.org/wiki/Applications_of_quantum_mechanics

Thanx! It really boils down to that most things will be the same in the "other" universes?

 

[Motore]

Thanx! It really boils down to that most things will be the same in the "other" universes?

I think so. But as we cannot acces other universes (if they exist) we cannot and will never know.

 

[GarberMoisha]

One thing, the physical world, such that we experince, is often about chemistry. Our thoghts are managed by synapses and transmittor substanses. these processes are not affected by waht spin a certain carbon atom in dopamine has? Or what spin an electron in a orbital in that atom has? So how does the quantum processes really change anything in the physical world?

All processes are fundamentally quantum. The open question is how they become classical, how does nature pull this trick. Because we observe an orderly, intuitive world which seems classical, but is not.
To whatever problem you have, even biological or medical, you will find a classical physics explnation.
Neurotransimitters mediate electrical circuits which are perceived as "classical". They can shift a neural circuit based on electrical conductivity and make you a schizophrenic. The number of your dopamine receptors in your brain cells determine what your thoughts will be wrt to mood, excitement, pleasure, obsession. Or insanity if they get too many.
Entirely classical process. Or as far as classical physics goes, which is a subset of the quantum.

 

[rolnor]

All processes are fundamentally quantum. The open question is how they become classical, how does nature pull this trick. Because we observe an orderly, intuitive world which seems classical, but is not.
To whatever problem you have, even biological or medical, you will find a classical physics explnation.
Neurotransimitters mediate electrical circuits which are perceived as "classical". They can shift a neural circuit based on electrical conductivity and make you a schizophrenic. The number of your dopamine receptors in your brain cells determine what your thoughts will be wrt to mood, excitement, pleasure, obsession. Or insanity if they get too many.
Entirely classical process. Or as far as classical physics goes, which is a subset of the quantum.

Thanx! Now we are getting somewhere. If we dont know how the Q-world affects the C-world, we dont know anything about the other universes, do we? Schizofrenia is a consequence of severe childhood trauma, the symptoms are increased dopamine activite, not the reason for it. According to many psycotherapists. its under debate.

 

[Motore]

Schizofrenia is a consequence of severe childhood trauma,

There is a possibility of this, not a fact. Studies show it's mostly genetics and other environmental factors:
https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC4940219&blobtype=pdf

 

[GarberMoisha]

Thanx! Now we are getting somewhere. If we dont know how the Q-world affects the C-world, we dont know anything about the other universes, do we? Schizofrenia is a consequence of severe childhood trauma, the symptoms are increased dopamine activite, not the reason for it. According to many psycotherapists. its under debate.

Not always, there are people who have never had childhood trauma who get schizophrenia. Which means it is not the cause. Stress certainly plays a part, as prolonged high level of cortisol causes neural damage(neuropathy). The driver of schizophrenia is an adverse autoimmune attack on enzymes that participate in the building of neutrotransmitters(I have dealt with such people for over a decade and have a close friend who is a professor psychiatrist and have open access to patients). Your neurotransmitters need to be within a specific threshold to perceive this reality as normal people do. Out of this range, birds start commenting in human language as you pass by them and you "hear" them talking(hallucinate).
This has a bearing on the current thread only as much as perception goes and how consistant it is. That schizophrenics don't agree on a single perceived reality as we normal people do, proves their distorted realities are bogus and not real. But they see and experience something that appears like a different world(reality).
Back to quantum physics. The brain does not need quantum mechanics. So far at least, there is no indication that quantum behavior, which is just nature preventing certain kind of knowledge, plays any part in brain's activity.

 

[rolnor]

Not always, there are people who have never had childhood trauma who get schizophrenia. Which means it is not the cause. Stress certainly plays a part, as prolonged high level of cortisol causes neural damage(neuropathy). The driver of schizophrenia is an adverse autoimmune attack on enzymes that participate in the building of neutrotransmitters(I have dealt with such people for over a decade and have a close friend who is a professor psychiatrist and have open access to patients). Your neurotransmitters need to be within a specific threshold to perceive this reality as normal people do. Out of this range, birds start commenting in human language as you pass by them and you "hear" them talking(hallucinate).
This has a bearing on the current thread only as much as perception goes and how consistant it is. That schizophrenics don't agree on a single perceived reality as we normal people do, proves their distorted realities are bogus and not real. But they see and experience something that appears like a different world(reality).
Back to quantum physics. The brain does not need quantum mechanics. So far at least, there is no indication that quantum behavior, which is just nature preventing certain kind of knowledge, plays any part in brain's activity.

Thanx, that says a lot about what changes could be found i the "alternate universes" mentioned in popular science. I have a psycosis illness myself and has studied litterature and gone in therapy fo 8years and to large degree feel well today. What you say is what psychiatrists say, no psycoanalysts. My mother has cronic psycosis and is not a very nice person, she has no friends whatsoever. Its a emotional problem, a consequence of bad parenting, not a neurotransmittor problem. My two brothers also suffer from mental illness. And my mother was physicaly abused as a child,

 

[Demystifier]

Why is our universe so "normal" if there is always a chance of strange things happening?

Strange things don't happen because their probability is too small. Typically, expectation time needed for them to happen is many orders of magnitude larger than the age of the universe.

 

[rolnor]

Strange things don't happen because their probability is too small. Typically, expectation time needed for them to happen is many orders of magnitude larger than the age of the universe.

OK, that means that the popscience idéas are wrong, D.Trump does not become president of Finland in some universe.

 

[Demystifier]

OK, that means that the popscience idéas are wrong, D.Trump does not become president of Finland in some universe.

Maybe he does, but then other circumstances in the other universe are also different, so that it doesn't look so strange after all.

 

[Drakkith]

The brain does not need quantum mechanics. So far at least, there is no indication that quantum behavior, which is just nature preventing certain kind of knowledge, plays any part in brain's activity.

To clarify for others, the brain's activity depends on the behavior of an enormous number of particles, each of which behaves according to quantum physics. The reason we don't usually talk about quantum effects on the brain is that nothing 'interesting' is going on. Everything averages out and behaves in a way that can be adequately described by classical physics. It's only when you get down to the scale of individual molecules and atoms that we are forced to get quantum physics involved. If some quantum effect occurs to make an enzyme bind with one nearby molecules instead of another nearby molecule, it just doesn't matter.

 

[rolnor]

To clarify for others, the brain's activity depends on the behavior of an enormous number of particles, each of which behaves according to quantum physics. The reason we don't usually talk about quantum effects on the brain is that nothing 'interesting' is going on. Everything averages out and behaves in a way that can be adequately described by classical physics. It's only when you get down to the scale of individual molecules and atoms that we are forced to get quantum physics involved. If some quantum effect occurs to make an enzyme bind with one nearby molecules instead of another nearby molecule, it just doesn't matter.

But is not this the case with all parts of the classical world, almost? That the Q-effects even out and nothing exciting, unusual will happen in the human world?

 

[hutchphd]

But is not this the case with all parts of the classical world, almost? That the Q-effects even out and nothing exciting, unusual will happen in the human world?

Almost. Almost.
But isn't that your definition of "exciting"? We seem to have a (rather silly) tautology.

 

[Drakkith]

But is not this the case with all parts of the classical world, almost? That the Q-effects even out and nothing exciting, unusual will happen in the human world?

Indeed. We're all doomed to a decidedly boring existence, never to experience the exciting effects of total disintegration via all of our particles simultaneously quantum tunneling to different locations. Well, probably not. There's always a chance.

 

[GarberMoisha]

But is not this the case with all parts of the classical world, almost? That the Q-effects even out and nothing exciting, unusual will happen in the human world?

The awareness that nature prevents certain kinds of knowledge, aka quantum behavior, resolves most if not all of the paradoxes.
The cat is there as you can ALWAYS infer something about it. If you isolated it WELL enough, you know it would be dead before you opened the lid, because the low temperature would kill it instantly.
Is the Moon there? Sure it is. All the time. There are so many ways to know about the Moon.
If you probed deep enough, at quantum scales, the Moon would prevent ascertaining certain joint quantities. But it does not mean that it doesn't exist.
People don't understand QT because of the wrong mindset with which they approach the subject.
Your mental illness is certainly grounded in medical circumstances and has classical physics at heart, like all problems we deal with. QM has nothing to do with it.

 

[rolnor]

Indeed. We're all doomed to a decidedly boring existence, never to experience the exciting effects of total disintegration via all of our particles simultaneously quantum tunneling to different locations. Well, probably not. There's always a chance.

Its silly for a reason, popular science describes the alternate universes as being possibly silly. Coffe can be green, greenland wins the soccer world cup etc.

 

[GarberMoisha]

There is zero evidence for other universes and based on their premises for the MWI, there NEVER will be.

 

[GarberMoisha]

Occam's razor deals easily with such propositions. Which for the MWI appears to be the most outlandish ever invented.

 

[PeterDonis]

the world we experience mostly seems to follow logic? The same logic year by year?

It's not a matter of logic, it's a matter of the laws of physics. More precisely, it's a matter of quantum events that happen according to the quantum laws of physics. Every time a quantum event happens that can have more than one outcome, the MWI says that all of the possible outcomes happen (and everything else in the universe gets entangled with the system that the event happened to, so that in each branch of the wave function, corresponding to each possible outcome of the event, the rest of the universe is consistent with that outcome).

Btw, "branch of the wave function" is the correct term in the MWI for what are being called "worlds" or "universes" in this thread. The MWI does not say there are multiple universes; there is only one. It says that this one universe consists of a wave function with lots and lots of branches.

So the correct way, under the MWI, to ask the kind of questions that are being asked in this thread is, "Is there a branch of the wave function in which X is true?" For example, "is there a branch of the wave function in which coffee is blue?" or "...in which Donald Trump gets elected President in 2024?", etc.

And the correct way to answer such questions is to look to see if there are any quantum mechanical events with multiple possible outcomes such that at least one of those outcomes would lead to X being true. And the first thing you realize about virtually all such questions when you consider this is that there is no way to answer them. The question about coffee being blue might be answerable in the negative, by showing that it is chemically impossible to have a substance with all of the properties of coffee except that it is blue in color--but even that would be difficult. But for the question about Trump being elected in 2024, for example, where would you even start?

In other words, the MWI is not a license to speculate that any outlandish thing you can dream up must be true in some branch of the wave function. Unfortunately, many pop science discussions of the MWI talk as if it does license exactly such speculations.

 

[rolnor]

It's not a matter of logic, it's a matter of the laws of physics. More precisely, it's a matter of quantum events that happen according to the quantum laws of physics. Every time a quantum event happens that can have more than one outcome, the MWI says that all of the possible outcomes happen (and everything else in the universe gets entangled with the system that the event happened to, so that in each branch of the wave function, corresponding to each possible outcome of the event, the rest of the universe is consistent with that outcome).

Btw, "branch of the wave function" is the correct term in the MWI for what are being called "worlds" or "universes" in this thread. The MWI does not say there are multiple universes; there is only one. It says that this one universe consists of a wave function with lots and lots of branches.

So the correct way, under the MWI, to ask the kind of questions that are being asked in this thread is, "Is there a branch of the wave function in which X is true?" For example, "is there a branch of the wave function in which coffee is blue?" or "...in which Donald Trump gets elected President in 2024?", etc.

And the correct way to answer such questions is to look to see if there are any quantum mechanical events with multiple possible outcomes such that at least one of those outcomes would lead to X being true. And the first thing you realize about virtually all such questions when you consider this is that there is no way to answer them. The question about coffee being blue might be answerable in the negative, by showing that it is chemically impossible to have a substance with all of the properties of coffee except that it is blue in color--but even that would be difficult. But for the question about Trump being elected in 2024, for example, where would you even start?

In other words, the MWI is not a license to speculate that any outlandish thing you can dream up must be true in some branch of the wave function. Unfortunately, many pop science discussions of the MWI talk as if it does license exactly such speculations.

Thanx, your text strengthens my feelings about popular sciences idéas, they are often or always 100% sure that coffe could be blue etc. and I get provoced by this. Its nice to hear that nobody really knows what all the branches could come up with, others in the thread say that quantum processes has very little or no effect on the thought process in our brain, this makes sence to me. What you say is also that the very name multiverse is inapropriate? Its the same universe? Multi-branch-universe (MBU) would be better?

 

[rolnor]

The awareness that nature prevents certain kinds of knowledge, aka quantum behavior, resolves most if not all of the paradoxes.
The cat is there as you can ALWAYS infer something about it. If you isolated it WELL enough, you know it would be dead before you opened the lid, because the low temperature would kill it instantly.
Is the Moon there? Sure it is. All the time. There are so many ways to know about the Moon.
If you probed deep enough, at quantum scales, the Moon would prevent ascertaining certain joint quantities. But it does not mean that it doesn't exist.
People don't understand QT because of the wrong mindset with which they approach the subject.
Your mental illness is certainly grounded in medical circumstances and has classical physics at heart, like all problems we deal with. QM has nothing to do with it.

I did not say my emotional problems is QM-based? Maybe I was unclear, sorry.

 

[rolnor]

Indeed. We're all doomed to a decidedly boring existence, never to experience the exciting effects of total disintegration via all of our particles simultaneously quantum tunneling to different locations. Well, probably not. There's always a chance.

Thanx Drakkith. All my frustrastion about the popular science version of MVT is gone now, I am grateful to all the authors in this topic.

 

[rolnor]

There is a possibility of this, not a fact. Studies show it's mostly genetics and other environmental factors:
https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC4940219&blobtype=pdf

Yes, its my own experience and knowledge, I am convinced of this but its not consensus in the academic world that I am right. (but I am right)

 

[PeterDonis]

What you say is also that the very name multiverse is inapropriate? Its the same universe?

Yes.

Multi-branch-universe (MBU) would be better?

Yes, I think that term is better than either "multiverse" or "many worlds".

 

[PeroK]

Occam's razor deals easily with such propositions. Which for the MWI appears to be the most outlandish ever invented.

MWI is the simplest interpretation of QM, but lacks a plausible derivation of the Born rule.

Applying Occam's razor zealously might lead to MWI, where the universe is no more than a single, evolving wavefunction.

 

[PeroK]

For those who believe the MWI is an impossibly bizarre interpretation of QM, the following post by Sean Carroll is worth reading. I'm not an advocate of MWI, but I agree with Carroll that it's sad when MWI is dismissed for what are "obviously wrong reasons".

https://www.preposterousuniverse.co...y-worlds-interpretation-of-quantum-mechanics/

 

[vanhees71]

Well, the two postulates (stated in a very imprecise way, but this we can overread to demonstrate good will)

1. Quantum states are represented by wave functions, which are vectors in a mathematical space called Hilbert space.
2. Wave functions evolve in time according to the Schrödinger equation.

Are not sufficient to serve as a physical theory. All you have is a partial differential equation to calculate a wave function, which represents quantum states, but this is just a nice PDE you may solve if you like, but there's no physics in it. For this physics you need an interpretation, i.e., the connection with what's observable in Nature, where I neither observe (by my senses or with whatever delicate technical equipment) wave functions nor Hilbert-space vectors. I need a description, what's the meaning of the Schrödinger equation. If it's a one-particle Schrödinger equation, standard QT assumes that its modulus squared describes the probability-density distribution for registering this particle at the time and position given by its arguments.

In the paper, Carroll quotes,

https://www.journals.uchicago.edu/doi/epdf/10.1093/bjps/axw004
https://arxiv.org/abs/1405.7577

however, he uses the standard formalism of defining states of subsystems of composite systems, namely the partial trace, now defining the state as given not by the wave functions but by statistical operators/density matrix (which of course is the only correct definition to begin with), and then using the standard interpretation of the density matrix to get the probabilities for the outcomes of measurements, leading to Born's rule, but isn't the density-matrix formalism just equivalent to Born's rule in its application to the special case of pure states (which are such states, for which the stat. op. is a projection operator, i.e., $\hat{\rho}^2=\hat{\rho}$)? So isn't he again assuming, in somewhat hidden form, just Born's rule?

I've nothing against the Everett interpretation per se, but I indeed only partially understand it, because it doesn't give a clear definition of the empirical meaning of the quantum state (probabilities in the minimally interpreted version of QT) and then pretends to derive Born's rule or the generalization to general states, defined via stat. ops. rather than "wave functions"/hilbert-space vectors.

Is there really no review/textbook, which just explains the Everett approach in a clear physicists' way as is done for orthodox QT, which I find way better (as long as one leaves out the collapse postulate and other oddities of the Copenhagen-interpretation mixtures) in just postulating the complete theory, including the probabilistic meaning of the quantum state right from the beginning, instead of pretending to derive it by just introducing it somehow assuming it through the "backdoor"?

 

[PeroK]

Well, the two postulates (stated in a very imprecise way, but this we can overread to demonstrate good will)

Are not sufficient to serve as a physical theory. All you have is a partial differential equation to calculate a wave function, which represents quantum states, but this is just a nice PDE you may solve if you like, but there's no physics in it. For this physics you need an interpretation, i.e., the connection with what's observable in Nature, where I neither observe (by my senses or with whatever delicate technical equipment) wave functions nor Hilbert-space vectors. I need a description, what's the meaning of the Schrödinger equation. If it's a one-particle Schrödinger equation, standard QT assumes that its modulus squared describes the probability-density distribution for registering this particle at the time and position given by its arguments.

This, IMO, sounds like a philosophical objection to the minimal MWI interpretation! Reading the paper below confirms my understanding that MWI is a minimalist interpretation. There is only the universal wavefunction - which behaves precisely according to orthodox QM. The difference is that MWI does not add a separate measurement process, but treats a measurement as just another QM unitary evolution. It has no need for the physical meaning that you are asking for.

In the paper, Carroll quotes,

https://www.journals.uchicago.edu/doi/epdf/10.1093/bjps/axw004
https://arxiv.org/abs/1405.7577

however, he uses the standard formalism of defining states of subsystems of composite systems, namely the partial trace, now defining the state as given not by the wave functions but by statistical operators/density matrix (which of course is the only correct definition to begin with), and then using the standard interpretation of the density matrix to get the probabilities for the outcomes of measurements, leading to Born's rule, but isn't the density-matrix formalism just equivalent to Born's rule in its application to the special case of pure states (which are such states, for which the stat. op. is a projection operator, i.e., $\hat{\rho}^2=\hat{\rho}$)? So isn't he again assuming, in somewhat hidden form, just Born's rule?

I've nothing against the Everett interpretation per se, but I indeed only partially understand it, because it doesn't give a clear definition of the empirical meaning of the quantum state (probabilities in the minimally interpreted version of QT) and then pretends to derive Born's rule or the generalization to general states, defined via stat. ops. rather than "wave functions"/hilbert-space vectors.

Is there really no review/textbook, which just explains the Everett approach in a clear physicists' way as is done for orthodox QT, which I find way better (as long as one leaves out the collapse postulate and other oddities of the Copenhagen-interpretation mixtures) in just postulating the complete theory, including the probabilistic meaning of the quantum state right from the beginning, instead of pretending to derive it by just introducing it somehow assuming it through the "backdoor"?

I'm not sure why the simplicity of MWI is not clear. For example, if we prepare a system and allow it to evolve unmeasured, then that is MWI. Only on a subsystem scale. MWI applies that same process and mathematics to the universe as a whole.

There may be objections to that - one of which is that it's not a satisfactory theory of the macroscopic physical universe that we believe we measure. Another is that the complexities of the measurement process are simply shifted to the complexities of justifying the Born rule.

In any case, MWI and what Carroll is saying seems quite straightforward to me.

 

[gentzen]

Is there really no review/textbook, which just explains the Everett approach in a clear physicists' way as is done for orthodox QT, which I find way better (as long as one leaves out the collapse postulate and other oddities of the Copenhagen-interpretation mixtures) in just postulating the complete theory, including the probabilistic meaning of the quantum state right from the beginning, instead of pretending to derive it by just introducing it somehow assuming it through the "backdoor"?

Lev Vaidman's SEP article Many-Worlds Interpretation of Quantum Mechanics should be a good no-nonsense review.
And Sean Carroll's Something Deeply Hidden should be a good readable book.

 

[PeroK]

Lev Vaidman's SEP article Many-Worlds Interpretation of Quantum Mechanics should be a good no-nonsense review.
And Sean Carroll's Something Deeply Hidden should be a good readable book.

I'm quite gratified that Vaidman makes the same point about Ockham's razor that I made above!