Let us consider relativistic particle (electron) which moves with relativistic speed v in the Coulomb field (in the field of a fixed heavy nucleus). The main question is what is the potential energy of a particle in such a static field? Landau and Lifshitz in their book "Field Theory" believe that the potential energy is not renormalized in any way and is equal to qQr. At the same time, a number of authors of original articles on this topic introduce a reduced distance r√1−v2/c2 into the denominator of this fraction due to the relativistic effect of the reduction in linear dimensions. Which of them is right?