Jakub Rembielinski

Unstable particles as open quantum systems

We present the probability preserving description of the decaying particle within the framework of quantum mechanics of open systems taking into account the superselection rule prohibiting the superposition of the particle and vacuum. In our approach the evolution of the system is given by a family of completely positive trace preserving maps forming one-parameter dynamical semigroup. We give the operator sum representation (Kraus representation) for the general evolution of such systems which allows to write the evolution for systems with two or more particles. We also show that there are remarkable restrictions on the possible strength of decoherence.