Doesn't MWI violate Lorentz Invariance?

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Discussion Overview

The discussion centers around whether the Many Worlds Interpretation (MWI) of quantum mechanics violates Lorentz invariance, particularly in the context of universe splitting. It explores the implications of various interpretations of quantum mechanics, including collapse interpretations and their relationship to relativistic theories, as well as the necessity of quantum field theory (QFT) for addressing these issues.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants argue that MWI may violate Lorentz symmetry when the universe splits.
  • Others point out that collapse interpretations also violate Lorentz invariance due to simultaneous wave function collapse.
  • There is a discussion about the non-relativistic nature of ordinary quantum mechanics and its limitations in addressing Lorentz invariance.
  • One participant questions why the community continues to discuss non-relativistic interpretations instead of moving directly to quantum field theory.
  • Another participant suggests that splitting in MWI is a result of continuous unitary evolution, which may not necessarily violate Lorentz symmetry unless unitary evolution itself does.
  • Concerns are raised about the interpretation of the Dirac and Klein-Gordon equations and their relationship to quantum field theory and Lorentz invariance.
  • One participant highlights that interpreting wave functions in non-relativistic quantum mechanics can lead to issues such as negative probabilities, suggesting a need for a specially relativistic interpretation.
  • There is a mention of negative energy solutions and antiparticles arising from the Dirac and Klein-Gordon equations.

Areas of Agreement / Disagreement

Participants express differing views on whether MWI and collapse interpretations violate Lorentz invariance. There is no consensus on the necessity of quantum field theory for addressing these interpretations or the implications of the Dirac and Klein-Gordon equations.

Contextual Notes

Participants note that the discussion involves unresolved mathematical steps and the dependence on interpretations of quantum mechanics. The implications of using non-relativistic quantum mechanics in contexts where relativistic effects may be significant remain unclear.

Nickyv2423
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Doesn't the Many Worlds Interpretation violate Lorentz symmetry when the universe splits?
 
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Yes, but so do collapse interpretations when the wave function collapses everywhere all at the same time. No matter what interpretation you use, "ordinary" quantum mechanics, the stuff you study in the first year or so of college QM, is non-relativistic and doesn't even pretend to be Lorentz invariant. You won't find a proper relativistic version of QM until you step up to quantum field theory.
 
Nugatory said:
Yes, but so do collapse interpretations when the wave function collapses everywhere all at the same time. No matter what interpretation you use, "ordinary" quantum mechanics, the stuff you study in the first year or so of college QM, is non-relativistic and doesn't even pretend to be Lorentz invariant. You won't find a proper relativistic version of QM until you step up to quantum field theory.

If this is so.. why do we keep discussing about non-relativistic version of Copenhagen or many worlds and whether there is collapse.. why didn't the community go directly to quantum field theory and the many worlds and Copenhagen version of QFT?
 
oquen said:
why didn't the community go directly to quantum field theory?
For the same reasons that we still study and use Newtonian mechanics instead of going directly to relativistic mechanics:
1) There is no "go directly"; you can't learn the relativistic theory until you understand and can use the simpler non-relativistic theory.
2) There are many important problems in which the relativistic effects are negligible. Using the relativistic theory for these adds enormous amounts of mathematical complexity and obscures the underlying physics without producing better answers or additional insight into the underlying physics.
 
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Nickyv2423 said:
Doesn't the Many Worlds Interpretation violate Lorentz symmetry when the universe splits?
Splitting is a result of continuous unitary evolution, so splitting as such does not necessarily violate Lorentz symmetry unless unitary evolution also violates it.
 
Nugatory said:
You won't find a proper relativistic version of QM until you step up to quantum field theory.
Why do you say that? The Dirac and Klein-Gordon equations do not require field theory. Neither does S-matrix theory. Or Wigner's prescription for a Lorentz transformation. I understand that there are plenty of good reasons for quantum field theory, but I don't see how Lorentz invariance requires it.
 
The Dirac and KG equations don't require QFT, true, BUT (and this is a big BUT) interpreting the wave function in these equations in terms of Copenhagen interpretation (and its Born rule) of non specially relativistic quantum mechanics is wrong (leads to the possibility of negative probabilities). One needs therefore an interpretation of specially relativistic quantum mechanics. The currently accepted one is actually a reformulation in terms of quantum fields and their regrettable mathematical problems.
 
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Hmm, Dirac leads to negative energy solutions and KG to negative probabilities with positive energies. Don't both lead to antiparticles?
 

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