Alpha-Particle Condensation in Nuclear Systems

The onset of quartetting, i.e. alpha-particle condensation, in symmetric and asymmetric nuclear matter is studied with the help of an in-medium modified four nucleon equation. It is found that at very low density quartetting wins over pairing, because of the strong binding of the alpha-particles. The critical temperature can reach values up to around 8 MeV. The disappearance of alpha-particles with increasing density, i.e. the Mott transition, is investigated. In finite nuclei the Hoyle state, that is the 0(2)(+) of C-12 is identified as an 'alpha-particle condensate' state. It is conjectured that such states also exist in heavier n alpha-nuclei, like O-16, Ne-20, etc. The sixth 0(+) state in O-16 is proposed as an analogue to the Hoyle state. The Gross-Pitaevski equation is employed to make an estimate of the maximum number of alpha particles a condensate state can contain. Possible quartet condensation in other systems is discussed briefly.