Cluster formation in asymmetric nuclear matter: Semi-classical and quantal approaches

The nuclear-matter liquid–gas phase transition induces instabilities against finite-size density fluctuations. This has implications for both heavy-ion-collision and compact-star physics. In this paper, we study the clusterization properties of nuclear matter in a scenario of spinodal decomposition, comparing three different approaches: the quantal RPA, its semi-classical limit (Vlasov method), and a hydrodynamical framework. The predictions related to clusterization are qualitatively in good agreement varying the approach and the nuclear interaction. Nevertheless, it is shown that (i) the quantum effects reduce the instability zone, and disfavor short-wavelength fluctuations; (ii) large differences appear between the two semi-classical approaches, which correspond respectively to a collisionless (Vlasov) and local equilibrium description (hydrodynamics); (iii) the isospin-distillation effect is stronger in the local equilibrium framework; (iv) important variations between the predicted time-scales of cluster formation appear near the borders of the instability region.