The physics of fast radio bursts

Fast radio bursts (FRBs), millisecond-duration bursts prevailing in the radio sky, are the latest large puzzle in the Universe and have been a subject of intense observational and theoretical investigations in recent years. The rapid accumulation of observational data has painted the following sketch about the physical origin of FRBs: They predominantly originate from cosmological distances, so their sources produce the most extreme coherent radio emission in the Universe; at least some, probably most, FRBs are repeating sources that do not invoke cataclysmic events; and at least some FRBs are produced by magnetars, neutron stars with the strongest magnetic fields in the Universe. Many open questions regarding the physical origin(s) and mechanism(s) of FRBs remain. This review addresses the phenomenology and possible underlying physics of FRBs. Topics include a summary of the observational data, basic plasma physics, general constraints on FRB models from the data, radiation mechanisms, source and environment models, and propagation effects, as well as FRBs as cosmological probes. Current pressing problems and future prospects are also discussed.