Exceptional points in open quantum systems

摘要: Open quantum systems are embedded in the continuum of scattering wavefunctions and naturally described by non-Hermitian Hamilton operators. In complex energy plane, exceptional points appear at which two (or more) eigenvalues operator coalesce. Although they a countable set single plane therefore measure zero, determine decisively dynamics open systems. A powerful method for description is Feshbach projection formalism. It used present paper as basic tool study role play Among others, topological structure points, rigidity phases eigenfunctions their vicinity, enhancement observable values due to reduced phase appearance transitions considered. The results compared with existing experimental data on microwave cavities. last section, some questions being still unsolved,