• Corpus ID: 115239950

Causality violation and nonlinear quantum mechanics

  title={Causality violation and nonlinear quantum mechanics},
  author={Jacques L. Pienaar},
  journal={arXiv: Quantum Physics},
  • J. Pienaar
  • Published 31 December 2013
  • Physics
  • arXiv: Quantum Physics
It is currently unknown whether the laws of physics permit time travel into the past. While general relativity indicates the theoretical possibility of causality violation, it is now widely accepted that a theory of quantum gravity must play an essential role in such cases. As a striking example, the logical paradoxes usually associated with causality violation can be resolved by quantum effects. We ask whether the explicit construction of a theory that allows causality violation might in turn… 
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  • Deutsch
  • Physics, Medicine
    Physical review. D, Particles and fields
  • 1991
Several novel and distinctive quantum-mechanical effects occur on and near closed timelike lines, including violations of the correspondence principle and of unitarity, and consideration of these sheds light on the nature of quantum mechanics.
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Unitarity and causality in generalized quantum mechanics for nonchronal spacetimes.
  • Hartle
  • Physics, Medicine
    Physical review. D, Particles and fields
  • 1994
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