  Heavy neutrino-antineutrino oscillations can naturally appear in mechanisms
of low scale neutrino mass generation, where pairs of heavy neutrinos have
almost degenerate masses. We discuss the case where the heavy neutrinos are
sufficiently long-lived to decay displaced from the primary vertex, such that
the oscillations of the heavy neutrinos into antineutrinos can potentially be
observed at the (high-luminosity) LHC and at currently planned future collider
experiments. The observation of these oscillations would have far-reaching
consequences: it would, for instance, prove the existence of lepton number
violation and the Majorana nature of neutrino masses, and it would allow a deep
insight into the nature of the neutrino mass generation mechanism.
