Quantum time crystals.

  title={Quantum time crystals.},
  author={Frank Wilczek},
  journal={Physical review letters},
  volume={109 16},
  • F. Wilczek
  • Published 12 February 2012
  • Physics
  • Physical review letters
Some subtleties and apparent difficulties associated with the notion of spontaneous breaking of time-translation symmetry in quantum mechanics are identified and resolved. A model exhibiting that phenomenon is displayed. The possibility and significance of breaking of imaginary time-translation symmetry is discussed. 

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