Electron-positron pair production by two identical photons in the nuclear field

In the Born approximation of the perturbation theory considered is a nonlinear effect of the electron-positron pair production by two identical photons in the Coulomb field of an atomic nucleus. The kinematic version of identical photons is studied. All the particles are considered to be nonpolarized. The calculation of the differential probability of the effect has been carried out earlier by the Feynman method. The total probability of the effect in limiting energy ranges is determined by integrating the formulas of the pair component distribution over energies. The probabilities of the electron-positron pair production and fusion of two photons into one in the nucleus field have been compared for the case of identical quanta. From the comparison of the results of analyzing both the nonlinear effects it follows that in the high-energy range the electron-positron pair production by two identical photons in the nucleus field extremely predominates over the fusion of two photons into one photon in the same field