Thermal properties of asymmetric nuclear matter are studied within a
self-consistent thermal model using an isospin and momentum dependent
interaction (MDI) constrained by the isospin diffusion data in heavy-ion
collisions, a momentum-independent interaction (MID), and an isoscalar
momentum-dependent interaction (eMDYI). In particular, we study the temperature
dependence of the isospin-dependent bulk and single-particle properties, the
mechanical and chemical instabilities, and liquid-gas phase transition in hot
asymmetric nuclear matter. Our results indicate that the temperature dependence
of the equation of state and the symmetry energy are not so sensitive to the
momentum dependence of the interaction. The symmetry energy at fixed density is
found to generally decrease with temperature and for the MDI interaction the
decrement is essentially due to the potential part. It is further shown that
only the low momentum part of the single-particle potential and the nucleon
effective mass increases significantly with temperature for the
momentum-dependent interactions. For the MDI interaction, the low momentum part
of the symmetry potential is significantly reduced with increasing temperature.
For the mechanical and chemical instabilities as well as the liquid-gas phase
transition in hot asymmetric nuclear matter, our results indicate that the
boundary of these instabilities and the phase-coexistence region generally
shrink with increasing temperature and is sensitive to the density dependence
of the symmetry energy and the isospin and momentum dependence of the nuclear
interaction, especially at higher temperatures.Comment: 21 pages, 29 figure