[en] The behavior of the two-particle Green's function in QED is analyzed in the limit when one of the particles becomes infinitely massive. It is found that the dependences of the Green's function on the relative times of the ingoing and outgoing particles factorize and that the bound state spectrum is the same as that of the Dirac equation with the static potential created by the heavy particle. The Bethe-Salpeter wave function is also determined in terms of the Dirac wave function. The present result excludes the existence, in the above limit, of abnormal solutions due to relative time excitations as predicted by the Bethe-Salpeter equation in the ladder approximation. (author)

[en] The recently developed technique of nonlocal regularization is applied to the two dimensional chiral Schwinger model, which is anomalous. It is shown that nonlocal regularization breaks the chiral gauge symmetry of the classical theory. However, the regularized theory belongs to a class of consistent theories considered by Jackiw and Rajaraman. (orig.)

[en] Electric charge in QED is topological in the sense that the electric current is a curl of a local gauge-invariant field - the dual electromagnetic field strength.Electrically charged particles are then visualized as topological solitons of V corresponding to elements of the homotopy group π (S¹) = Z. The quantization of electric charge and the universality of the electromagnetic coupling are thus given a topological interpretation. The low energy physics is described by a 'dual' Lagrangian written in terms of the field V only. The vortex field V is also constructed in non-Abelian gauge theories. Here the solitons of V are identified with the 'constituent' quarks. The dual Lagrangian contains explicit flux-symmetry-breaking terms. As a result the topological solitons (quarks) are linearly confined. In this paper, the authors describe in detail the derivation of the dual Lagrangian and the topological mechanism of confinement in non-Abelian theories with adjoint and fundamental matter. The extension of the above description to the (3 + 1)-dimensional gauge theories is briefly discussed. Several notions are easily generalizable but the picture is far form being complete

[en] Very precise investigations of the positron-electron pair production by γ-quanta of 6.13 MeV showed at every single case that the energy sums of the two particles are significantly lower than the energies of the involved quanta. Further on the energy spectra of the positrons and electrons are very different from each other. This is in a direct contradiction to the existing general opinion accepted by nearly all physicists which says that they should be identical. Following own calculations of the author and also the measurements discussed in this paper, we come to the conclusion that the theory of pair creation must be modified, to bring it in a form to include also the above presented new effects. It can be shown, that the well known 'hole theory' of Dirac from 1932 agrees very well with the new results of the observations. Especially the energy deficits of the positrons and electrons and their spectra will be described correctly. (orig.) With 9 figs

[en] We present in a path integral framework a class of gauges for QED that are both temporal and yet do not display the notorious singularity of the naive temporal gauge. These gauges follow from a generalised radiation gauge, where the Coulomb gauge fixing is 'smeared out'. We show that the use of two gauge fixings necessitates the incorporation of gauge dependent Coulomb interactions. The correctness of our theory is demonstrated in two ways: We can reduce to the true degrees of freedom and we show that it reproduces some gaugeinvariant results of perturbation theory. Although Landshoff's α prescription for the temporal gauge can be understood as a limit of our class, extra terms also appear. It is seen that these terms are necessary to obtain the periodic Wilson loop at finite temperature correctly. (orig.)

[en] We show that discontinuities in the vacuum polarisation give rise to charge screening effects which are large and result in a lower bound Δ with -m<Δ