Compatibility of MWI with probability of outcomes

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Discussion Overview

The discussion centers on the Many-Worlds Interpretation (MWI) of quantum mechanics, particularly its ability to account for the probabilities of outcomes as described by the Born rule. Participants explore the implications of MWI on the nature of probability, entanglement, and the measurement problem, raising questions about the coherence of these concepts within the framework of MWI.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation
  • Exploratory

Main Points Raised

  • Some participants question whether MWI can adequately explain the probabilities of outcomes, particularly in relation to the Born rule.
  • One participant suggests that if all outcomes are realized in MWI, then the probability of any specific outcome occurring should be 100%.
  • Another participant argues that while MWI implies all outcomes occur, it does not clarify how this aligns with the observed probabilities dictated by the Born rule.
  • There are mentions of Sean Carroll's approach to deriving the Born rule within MWI, which involves assigning equal epistemic probabilities to branches with equal amplitudes, though some express skepticism about its acceptance.
  • Concerns are raised about the implications of observers being "branch bound," leading to potential biases in memory and perception of outcomes.
  • Some participants discuss the assumption of unitary evolution in MWI and its relationship to the Born rule, noting that the inability to derive the Born rule from unitary evolution presents an open issue.
  • There is a suggestion that if MWI cannot reconstruct the Born rule, it raises questions about the validity of unitary evolution as a fundamental principle.
  • One participant posits that observers tied to a single branch since the universe's inception might explain the observed probabilities, but this remains contested.
  • Another participant emphasizes that the Born rule and unitary evolution can coexist as postulates in quantum mechanics, but questions arise about their reconciliation in the context of MWI.
  • The discussion touches on the nature of relative frequencies of outcomes in different branches and how this relates to the perception of probabilities.

Areas of Agreement / Disagreement

Participants express a range of views, with no consensus reached on whether MWI can satisfactorily account for the probabilities of outcomes or the Born rule. Several points of contention remain regarding the implications of unitary evolution and the nature of observer experiences within MWI.

Contextual Notes

Limitations include the unresolved status of the Born rule within MWI, the dependence on interpretations of entanglement, and the assumptions regarding observer experiences and biases. The discussion reflects ongoing debates in the interpretation of quantum mechanics.

  • #31
entropy1 said:
Determinism can involve retrocausality I think. Or rather, correlation, as a combination of causality and retrocausality.
In the Many Worlds Interpretation? In any case, wouldn't it still be determinism? So the outcomes necessarily follow from the initial conditions. I'm sorry, maybe I don't understand what you are driving at.
 
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  • #32
Minnesota Joe said:
In the Many Worlds Interpretation? In any case, wouldn't it still be determinism? So the outcomes necessarily follow from the initial conditions. I'm sorry, maybe I don't understand what you are driving at.
Ok, let me be clearer: IF A -> B, or: "IF A THEN B", then you could say A and B are causally linked. But they are also retrocausally linked, because the equivalent assertion is: NOT-B -> NOT-A, or: "IF NOT B THEN NOT A". The rule is deterministic, but the values are left to fill in. If you fill in A, B follows, but if you fill in (NOT-)B, (NOT-)A follows. The question remains: who determines what?
 
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  • #33
entropy1 said:
Ok, let me be clearer: IF A -> B, or: "IF A THEN B", then you could say A and B are causally linked. But they are also retrocausally linked, because the equivalent assertion is: NOT-B -> NOT-A, or: "IF NOT B THEN NOT A". The rule is deterministic, but the values are left to fill in. If you fill in A, B follows, but if you fill in (NOT-)B, (NOT-)A follows. The question remains: who determines what?
I'm still not sure what you mean. "If A then B, A, therefore B" concludes something quite different than, "If not-B then not-A, not-B, therefore not-A". They contradict each other on the common reading, since it is not possible that (A & not-A). They can't both be true. If, instead, you are referring to conditions on the wavefunction being specified at ##t_1## compared to some later ##t_2##, then they have to be consistent with each other. You should be able to derive the first conditions from the second conditions and visa versa, just using the Schrödinger equation.
 
  • #34
Minnesota Joe said:
If, instead, you are referring to conditions on the wavefunction being specified at ##t_1## compared to some later ##t_2##, then they have to be consistent with each other. You should be able to derive the first conditions from the second conditions and visa versa, just using the Schrödinger equation.
Then I think you are talking about A <-> B, or (A -> B) AND (B -> A), which is equivalent to NOT-A <-> NOT B. I distinguish the rule and the values. You may think of fixed rules, but who fills in which values? I think that in the deterministic view of QM, MWI, this is solved by yielding all possible outcomes (all possible values). But I have to say I am not a physicist.
 
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  • #35
entropy1 said:
Then I think you are talking about A <-> B, or (A -> B) AND (B -> A), which is equivalent to NOT-A <-> NOT B. I distinguish the rule and the values. You may think of fixed rules, but who fills in which values?
Who or (I'm more inclined to say) what sets the initial conditions for the universal wavefuction is irrelevant to the point. After they are set, everything is determined by the Schrödinger equation. That includes our actions and observations. I'm talking about MWI in particular of course. Something analogous would follow for other deterministic theories of QM, but the equations would be different. Do you disagree with what I've written?
 
  • #36
entropy1 said:
COULD you say that the outcome is not determined until observed, and NOT EVEN determined AFTER that because we have the superposition of ALL outcomes?

No. MWI is always deterministic.

The correct way to say it is the way I have already said it.

entropy1 said:
To be speculative

Personal speculations are out of bounds.
 
  • #37
The OP question has been answered and the thread is becoming speculative. Thread closed.
 

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