Counterfactual Definiteness and MWI in Wiki

  • Thread starter TunnelingthuWorlds
  • Start date
  • Tags
    cfd mwi
In summary, Counterfactual Definiteness and Many World's Interpretation are two concepts used in quantum mechanics to understand the existence and properties of unmeasured results. Counterfactual Definiteness refers to the ability to speak meaningfully about these unmeasured results in statistical calculations, while Many World's Interpretation rejects this concept and instead assigns multiple values to measurements that are performed. This leads to a branching reality where each value is realized in a different world. Prof. Guy Blaylock of the University of Massachusetts Amherst states that the MWI is not only counterfactually indefinite, but also factually indefinite. However, the MWI is not considered superdeterministic as it does not fine-tune initial conditions to
  • #1
TunnelingthuWorlds
13
0
TL;DR Summary
Counterfactual Definitiveness and Many World's Interpretation
Summary: Counterfactual Definitiveness and Many World's Interpretation

Sorry for all these threads, my noetic fluids and bursting.

Wiki states the following:

In quantum mechanics, counterfactual definiteness (CFD) is the ability to speak "meaningfully" of the definiteness of the results of measurements that have not been performed (i.e., the ability to assume the existence of objects, and properties of objects, even when they have not been measured). The term "counterfactual definiteness" is used in discussions of physics calculations, especially those related to the phenomenon called quantum entanglement and those related to the Bell inequalities.[1] In such discussions "meaningfully" means the ability to treat these unmeasured results on an equal footing with measured results in statistical calculations. It is this (sometimes assumed but unstated) aspect of counterfactual definiteness that is of direct relevance to physics and mathematical models of physical systems and not philosophical concerns regarding the meaning of unmeasured results.
"Counterfactual" may appear in physics discussions as a noun. What is meant in this context is "a value that could have been measured but, for one reason or another, was not.Then proceeds to state in regards to the import of CFD to MWI:

The Many Worlds interpretation rejects counterfactual definiteness in a different sense; instead of not assigning a value to measurements that were not performed, it ascribes many values. When measurements are performed each of these values gets realized as the resulting value in a different world of a branching reality. Thus although unperformed experiments have values, they cannot be used in statistical calculations as one would the single value of a performed experiment. As Prof. Guy Blaylock of the University of Massachusetts Amherst puts it, "The many-worlds interpretation is not only counterfactually indefinite, it is factually indefinite as well." [19]

Can someone help me understate the part Prof. Guy Blaylock is pointing towards, and whether or not you agree with everything as stated?
 
Physics news on Phys.org
  • #2
TunnelingthuWorlds said:
Wiki states the following

What Wikipedia article are you quoting from? Please provide a link.
 
  • #4
TunnelingthuWorlds said:
Can someone help me understate the part Prof. Guy Blaylock is pointing towards

He's saying that the MWI is not "factually definite" because it does not assign a single unique result to a measurement that is performed; it assigns multiple results.

TunnelingthuWorlds said:
whether or not you agree with everything as stated?

The statement about the MWI not being "factually definite" in the sense I described above is correct.

I don't think the statement about how the MWI denies counterfactual definiteness is correct. The MWI does not assign any result to measurements that are not performed. It assigns multiple results to measurements that are performed.
 
  • #5
PeterDonis said:
He's saying that the MWI is not "factually definite" because it does not assign a single unique result to a measurement that is performed; it assigns multiple results.
But, I thought MWI was superdeterministic. Hence, the decidability of outcomes is predetermined, are they not?
 
  • #6
TunnelingthuWorlds said:
I thought MWI was superdeterministic

Why do you think that?
 
  • #7
PeterDonis said:
Why do you think that?
Wiki again:
The many-worlds interpretation (MWI) is an interpretation of quantum mechanics that asserts that the universal wavefunction is objectively real, and that there is no wavefunction collapse.[2] This implies that all possible outcomes of quantum measurements are physically realized in some "world" or universe.[3] In contrast to some other interpretations, such as the Copenhagen interpretation, the evolution of reality as a whole in MWI is rigidly deterministic.[2]

Click on [2]
 
  • #8
  • #9
None of your quotes contain the word “superdeterministic”...
 
  • #10
TunnelingthuWorlds said:
But, I thought MWI was superdeterministic. Hence, the decidability of outcomes is predetermined, are they not?
In MWI the outcomes are predetermined, meaning that it is deterministic. But it is not superdeterministic. Superdeterministic means that initial conditions are fine tuned so that the particular solution (of the equations of motion) associated with those initial conditions obeys a rule that most other solutions do not obey.
 
  • #11
Demystifier said:
In MWI the outcomes are predetermined, meaning that it is deterministic. But it is not superdeterministic. Superdeterministic means that initial conditions are fine tuned so that the particular solution (of the equations of motion) associated with those initial conditions obeys a rule that most other solutions do not obey.
But, if the wavefunction keeps on evolving, then each iteration or (insert word for a system that evolves on its own without external input), then doesn't that mean that the initial conditions were fine-tuned?
 
  • #12
TunnelingthuWorlds said:
But, if the wavefunction keeps on evolving, then each iteration or (insert word for a system that evolves on its own without external input), then doesn't that mean that the initial conditions were fine-tuned?
Not really. It is quite a generic property for all solutions with a low coarse-grained entropy. Of course, most solutions do not have a low coarse-grained entropy, so there is some "fine tuning" involved. Essentially, that's the "fine tuning" that is needed for the emergence of the 2nd law of thermodynamics. But apart from the 2nd law, there is no any other independent law that emerges from such "fine tuning". Hence it is a rather mild form of "fine tuning" so it is usually not viewed as superdeterminism. A more precise way to express this idea is to note that a low entropy initial state has low complexity, while a truly fine tuned initial condition has to have a large complexity.
 
  • #13
Demystifier said:
Not really. It is quite a generic property for all solutions with a low coarse-grained entropy. Of course, most solutions do not have a low coarse-grained entropy, so there is some "fine tuning" involved. Essentially, that's the "fine tuning" that is needed for the emergence of the 2nd law of thermodynamics. But apart from the 2nd law, there is no any other independent law that emerges from such "fine tuning". Hence it is a rather mild form of "fine tuning" so it is usually not viewed as superdeterminism. A more precise way to express this idea is to note that a low entropy initial state has low complexity, while a truly fine tuned initial condition has to have a large complexity.
So, didn't you just describe the dynamics of the wavefunction here or can it possibly be a top-down approach instead of a bottom-up one in this case?
 
  • #14
TunnelingthuWorlds said:
So, didn't you just describe the dynamics of the wavefunction here
Yes I did.

TunnelingthuWorlds said:
or can it possibly be a top-down approach instead of a bottom-up one in this case?
It's a bottom-up description.
 
  • #15
Demystifier said:
It's a bottom-up description.
Without deviating from this great thread, what is the consensus amongst physicists, and mathematicians?
 
  • #16
TunnelingthuWorlds said:
Without deviating from this great thread, what is the consensus amongst physicists, and mathematicians?
Consensus about what? Perhaps you mean consensus about whether physics should be done bottom-up or top-down? In that case the consensus is that the fundamental laws are to be searched in a top-down manner, but once they are found they are to be used in the bottom-up manner.
 
  • #17
TunnelingthuWorlds said:
Wiki again

None of what you quote says that the MWI is superdeterministic, just that it is deterministic.
 
  • #19
TunnelingthuWorlds said:
I'm churning through this thread

Which also doesn't say the MWI is superdeterministic. The thread title asks a question, and the answer to the question is no.
 
  • #20
Ok, then it's rigidly deterministic.

Can we stop the pissing contest?
 
  • #21
TunnelingthuWorlds said:
Ok, then it's rigidly deterministic.

Can we stop the pissing contest?
Superdeterministic and deterministic are different terms with very different implications, they have to be kept separate. And @PeterDonis is correct, Many Worlds is not superdeterministic.
 
  • #22
TunnelingthuWorlds said:
Can we stop the pissing contest?

You're the one that raised the issue of the MWI being superdeterministic. We are simply answering your question. This attitude is not called for, and has just got you a warning and your thread closed (and your original question has been answered anyway).
 

FAQ: Counterfactual Definiteness and MWI in Wiki

1. What is Counterfactual Definiteness?

Counterfactual Definiteness is a concept in quantum mechanics that states that every physical property of a system has a definite value, even if it is not being measured or observed.

2. What is the Many-Worlds Interpretation (MWI)?

The Many-Worlds Interpretation is a theory in quantum mechanics that suggests that every possible outcome of a quantum event actually occurs in a separate parallel universe. It proposes that the universe constantly splits into multiple parallel universes to accommodate all the different outcomes of quantum events.

3. How does MWI relate to Counterfactual Definiteness?

MWI provides a possible explanation for the counterintuitive concept of Counterfactual Definiteness. In MWI, the existence of parallel universes allows for all possible outcomes of a quantum event to occur, thus satisfying the requirement of Counterfactual Definiteness.

4. What evidence supports MWI and Counterfactual Definiteness?

There is currently no direct experimental evidence for MWI and Counterfactual Definiteness. However, some physicists argue that MWI is a more elegant and simpler explanation for certain quantum phenomena, such as the double-slit experiment, than other interpretations.

5. What are the implications of MWI and Counterfactual Definiteness?

The implications of MWI and Counterfactual Definiteness are still being debated among scientists. Some argue that it challenges our understanding of reality and raises questions about the nature of consciousness. Others suggest that it has no practical implications and is simply a mathematical interpretation of quantum mechanics.

Similar threads

Back
Top