Speaker
Prof.
Ilya Ginzburg
(Sobolev Institute of Mathematics)
Description
3 topics appeared in the description of processes with unstable particles. 1. Plane wave formalism is insufficient for some realistic problems. The wave packets formalism become necessary. Illustration:The t--channel singularity in small angle scattering. 2. Perturbation series become invalid like in the case of infrared divergence in QED, but in more strong form. Illustration: The s--channel singularity near the threshold. 3. Theory with unstable fundamental particles don't allow conditions for construction of perturbation diagrammatic expansion. Signature: Gauge dependence in the description of observable processes in higher orders
