Proceedings of the Workshop on Calculation of Double-Beta-Decay Matrix Elements (MEDEX'17)

The MEDEX (Matrix Elements for the Double beta decay Experiments) meeting is dedicated to the presentation of different methods of nuclear matrix elements (NME) calculations in connection with nuclear double beta decay processes. Several double beta decay experiments have been taking data with quantities of enriched isotopes around or above 100 kg and plans are under way for tonne-scale experiments. These efforts revolve around several isotopes and use a broad array of detection techniques (KamLAND-ZEN, SNO+, EXO-200/nEXO, GERDA, CUORE, SuperNEMO, COBRA, Majorana...). Experiments of such scale make enormous demands on the progress and reliability of the nuclear matrix elements calculations. Also the research in the field of special modes of ββ, such as β+ β or 2νECEC starts to be more and more interesting from experimental and theoretical points of view (e.g. COBRA, TGV,...). Further development of the theory of such processes is crucial for continuation of the experimental activities in this field.