Rôle de l'isospin dans la transition de phase liquide-gaz de la matière nucléaire

Abstract : Nuclear matter presents a phase transition of the liquid-gas type. This well-known feature is due to the nuclear interaction profile (mean-range attractive, short-range repulsive). Symmetric-nuclear-matter thermodynamics is thus analogous to that of a Van der Waals fluid. The study shows up to be more complex in the case of asymmetric matter, composed of neutrons and protons in an arbitrary proportion. Isospin, which distinguishes both constituents, gives a measure of this proportion. Studying asymmetric matter, isospin is an additional degree of freedom, which means one more dimension to consider in the space of observables.
The nuclear liquid-gas transition is associated with the multi-fragmentation phenomenon observed in heavy-ion collisions, and to compact-star physics : the involved systems are neutron rich, so they are affected by the isospin degree of freedom.
The present work is a theoretical study of isospin effects which appear in the asymmetric-nuclear-matter liquid-gas phase transition. A mean-field approach is used, with a Skyrme nuclear effective interaction. We demonstrate the presence of a first-order phase transition for asymmetric matter, and study the isospin distillation phenomenon associated with this transition. The case of phase separation at thermodynamic equilibrium is compared to spinodal decomposition. Finite size effects are addressed, as well as the influence of the electron gas which is present in the astrophysical context.
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Contributor : Camille Ducoin <>
Submitted on : Friday, October 27, 2006 - 4:12:32 PM
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  • HAL Id : tel-00110371, version 1

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C. Ducoin. Rôle de l'isospin dans la transition de phase liquide-gaz de la matière nucléaire. Physique Nucléaire Théorique [nucl-th]. Université de Caen, 2006. Français. ⟨tel-00110371⟩

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