Time crystals in primordial perturbations
  Cosmological time crystal (TC) corresponds to a matter state where the
periodic motion of field forms a limit cycle in its phase space. We explore
what would happen if it existed in inflationary phase. It is found that the
limit cycle responsible for TC will inevitably cause the periodic oscillation
of the primordial perturbation spectrum. The oscillatory patterns of the
spectrum depend on the TC parameters, and so encode the crystalline patterns of
TC.
