Quantum revivals in free field CFT
  A commentary is made on the recent work by Cardy, ArXiv:1603. 08267, on quantum revivals and higher dimensional CFT. The actual expressions used here are those derived some time ago. The calculation is extended to fermion fields for which the power spectrum involves the odd divisor function. Comments are made on the equivalence of operator counting and eigenvalue methods, which is quickly verified. An explanation of the rational revivals for odd spheres is given in terms of wrongly quantised fields. 
J.S. Dowker
hep-th cond-mat.stat-mech quant-ph