Microscopic origin of pairing

A brief review of recent progress in the ab intio theory of nuclear pairing is given. Nowdays several successful solutions of the ab intio BCS theory gap equation were published which show that it is a promising first step in the problem. However, the role of many-body correlations that go beyond the BCS scheme remains uncertain and requires further investigations. As an alternative, the semi-microscopic model is discussed in which the effective pairing interaction calculated from the first principles is supplemented with a small phenomenological addendum containing one phenomenological parameter universal for all medium and heavy atomic nuclei.