Comment on "Quantum Time Crystals": a new paradigm or just another   proposal of perpetuum mobile?
  A Comment on Frank Wilczek's paper "Quantum Time Crystals" (Phys. Rev. Lett. 109, 160401 (2012); arXiv:1202.2539). 
Patrick Bruno
quant-ph cond-mat.other cond-mat.quant-gas cond-mat.supr-con