THE concept of an ideal fluid is applicable in two limiting cases of relativistic hydrodynamics: at sufficiently low temperatures, when the mean number of produced pairs is much smaller than the number of virtual particles, and in the ultra-relativistic case of super-high temperatures, when the mean number of pairs is much larger than the number of virtual particles. In fact, it follows from the equations t
A brief review is given of the principal results achieved by M. A. Leontovich in electrodynamics. Among them are approximate boundary conditions on the surface of a good conductor, the parabolic equation method for solving diffraction problems, the theory of thin antennas, the inertial theory of constriction of a powerful pulsed discharge, conditions for suppressing the kink instability of a current-carrying conductor, and other results.