On some peculiarities of EAS initiated by gamma rays of extremely high energies

The number of low energy muons (Eμ≤1GeV) in EAS initiated by primary gamma rays of extremely high energies is calculated. It is shown that at large depths the number of low-energy muons in EAS from gamma rays with energy E0≥1018eV is of the same order as in the proton-induced shower, as opposed to the energy range E0∼1015eV, where the gamma showers are ''muon-poor''. The influence of the Landau-Pomeranchuk-Migdal effect and of the interaction of the primary photon with the geomagnetic field on the development of an electromagnetic shower in the Earth's atmosphere at energies E0≥1019eV is investigated. In case of a high content of gamma rays in the primary cosmic radiation (γ/P>0.1) one should not ignore these effects when interpreting data on EAS of extremely high energies. (author)