title: Impossibility of spontaneously rotating time crystals: a no-go theorem.
abstract: I present arguments indicating the impossibility of spontaneously rotating "quantum time crystals," as recently proposed by Frank Wilczek. In particular, I prove a "no-go theorem," rigorously ruling out the possibility of spontaneous ground-state (or thermal equilibrium) rotation for a broad class of systems.
authors.affiliation: European Synchrotron Radiation Facility, Grenoble, France. patrick.bruno@esrf.fr
authors.forename: Patrick
authors.initials: P
authors.lastname: Bruno