Cause and effect and quantum field theory

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Discussion Overview

The discussion centers on the relationship between cause and effect in quantum mechanics and quantum field theory (QFT). Participants explore whether QFT offers a different interpretation of causality compared to classical physics, particularly in light of the Heisenberg Uncertainty Principle and the implications of local versus nonlocal causality.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant asserts that quantum mechanics replaces classical cause and effect with probabilities, questioning if QFT provides a different interpretation or mitigates the impact on causality.
  • Another participant argues that quantum mechanics refines rather than replaces classical concepts, suggesting that there is no damage to causality in either QM or QFT.
  • A third participant states that classical relativity maintains local causality, which they claim is not upheld in relativistic QFT, although information transmission remains limited to the speed of light.
  • In response, another participant challenges the claim of incompatibility with local causality, stating that local causality is preserved in the locality of the Lagrangian density and dispersion relations in relativistic QFT, and that nonlocal correlations do not imply causality violations.

Areas of Agreement / Disagreement

Participants express differing views on the nature of causality in quantum mechanics and QFT, with no consensus reached on whether QFT alters the classical understanding of causality or if local causality is maintained.

Contextual Notes

Participants reference the Heisenberg Uncertainty Principle, local causality, and nonlocal correlations, but the discussion does not resolve the implications of these concepts within the frameworks of QM and QFT.

arupel
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Quantum mechanics replaces the classical concept of cause and effect with probabilities. The best explanation: it just is.

While the Heisenberg Uncertainty Principles hold in quantum field theory does QFT offer a different interpretation to this concept? Or at least mitigate some of the damage done to it.
 
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QM doesn't replace. It refines. Different matter.
And I don't see any damage whatsoever, neither in QM nor in QFT that builds on QM.
 
Classical relativity is a theory of local causality.

This is no longer true in relativistic QFT, which is incompatible with local causality. What is common to both classical and quantum relativity is that information cannot be communicated faster than light.
 
atyy said:
This is no longer true in relativistic QFT, which is incompatible with local causality.
This is not true. Local causality is classically embodied in the locality of the Lagrangian density and the dispersion relations for scattering, and both still hold in relativistic QFT. Nonlocal correlations as demonstrated by Bell inequalities have nothing to do with causality violations.
 
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