Remarks on the vacuum polarisation of an external electric field based on non-perturbative methods

Model calculations and physical arguments are used to indicate the probability that the divergences of quantum electrodynamics (QED) come largely from the application of perturbation theory. In a non-perturbative treatment of QED, where from the beginning the self-interaction of the vacuum is taken into account, these divergences are at least remarkably reduced and it can be hoped that in the renormalisation procedure of QED (and also other gauge theories) all ultraviolet divergences disappear. (author)