  Neutrinos are the most elusive among the known elementary particles, because
of their feeble interactions with ordinary matter. They are also the most
mysterious, because of their tiny masses that suggest a novel mass generating
mechanism, their unknown Dirac or Majorana nature, and their big quantum mixing
leading to large-amplitude flavor oscillations. This Topical Group focuses on
neutrino properties that are not directly investigated in other Topical Groups
of the Neutrino Frontier: in particular, the absolute value of the neutrino
masses, the Dirac or Majorana nature of neutrinos, their electromagnetic
properties, their lifetime, and hypothetical exotic properties.
