On the origin of FRBs

Fast Radio Bursts (FRBs) is still an enigmatic phenomenon, even after more than a decade from their discovery. These are short radio pulses of tens of milliseconds duration (intrinsic) in the frequency range around a gigaherz and exhibiting very large dispersion measure, which is indicative of their extragalactic origin and, hence, of their exceptional brightness. Conventionally, FRBs are attributed to the cyclotron/synchrotron maser instability exciting an X-mode in a strong shock environment. We will discuss viability of this mechanism. We will also discuss whether FRBs can originate deep inside a magnetosphere of a magnetar and the role of QED and plasma effects.