Quantum electrodynamics of superstrong fields

Some aspects of quantum electrodynamics of superstrong fields are considered. Physical phenomena in superstrong nuclei with Z charge greater than the critical Zcr. are discussed. For such nuclei the discrete electron spectrum level falls into low continuum. The analysis of phenomena is performed on the basis of the effective potential method. For experimental observation of phenomena taking place at Z>Zcr. one should posses nuclei with Z=170 which falls far outside the limits of the field of known nowadays stable nuclei. However electric fields of the proper value may be attained in the course of two heavy ions collision. It heavy nuclei collisions at the distances less than of a certain critical one the discrete electron level passes into the low continuum and a spontaneous positron production occurs. It is pointed out that physical phenomena taking place at the transition of discrete levels into the low continuum follow from the analysis of exact solutions of Dirac equations in the region of superstrong fields. For the last years first experiments have been performed on observation of positrons produced on irradiation of 238U, 208Pb, 194Au, 181Ta and 139La targets by lead and uranium ion beams