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Theoretical Issues in Nuclear Astrophysics, Orsay : France (2007)
Instability against cluster formation in nuclear and compact-star matter
C. Ducoin1, Ph. Chomaz2, F. Gulminelli1

Nuclear matter is known to present a phase transition of the liquid-gas type : this implies that homogeneous matter at sub-saturation density can be unstable against finite-size density fluctuations, leading to the formation of clusters. This is also true for asymmetric matter, concerning a well-defined region of the neutron-proton density plane : for each temperature, the instability region is determined by the curvature properties of the free energy in this plane. This feature applies to low-density star matter, which we describe as nuclear matter (treated in mean field) whose proton charge is neutralized by an electron Fermi gas. Assuming beta equilibrium imposes star-matter composition, depending on the fraction of neutrinos retained in the stellar medium : this determines whether homogeneous matter is inside the instability region or not. Since, in reverse, neutrino propagation depends on matter inhomogeneities, there should be an interconnection between neutrino presence and star matter clusterization.
1 :  LPCC - Laboratoire de Physique Corpusculaire de Caen
2 :  GANIL - Grand Accélérateur National d'Ions Lourds
Physique théorique
Physique/Physique Nucléaire Théorique