  Open Quantum System (OQS) description of a many-body system involves
interaction of Shell Model (SM) states through the particle continuum. In
realistic nuclear applications, this interaction may lead to collective
phenomena in the ensemble of SM states. We claim that the nuclear clustering is
an emergent, near-threshold phenomenon, which cannot be elucidated within the
Closed Quantum System (CQS) framework. We approach this problem by
investigating the near-threshold behavior of Exceptional Points (EPs) in the
realistic Continuum Shell Model (CSM). The consequences for the
alpha-clustering phenomenon are discussed.
