Cosmic gamma-ray bursts

The properties of the cosmic Gamma-ray Bursts (GRBs) are briefly summarized. Two fundamental theoretical problems are pointed out: the problem of the energy source, and the problem of compactness. The possible connection of GRBs with the Dark Matter candidates is mentioned. I argue that GRBs may be produced by collapses or mergers of stars made of ‘mirror’ matter. The mirror neutrinos (which are sterile for our matter) produced at these events can oscillate into ordinary neutrinos. The annihilations of the latter create an electron-positron plasma and subsequent relativistic fireball with a very low baryon loading needed for GRBs. The concept of mirror matter is able to explain several key problems of modern astrophysics: deficit of solar and atmospheric neutrino, the missing mass, MACHO microlensing events and GRBs. I speculate on the impact that the parameters of the neutrino oscillations might have on the observed properties of GRBs if the latter are the products of collapses or mergers of mirror stars.