Speed of sound in asymmetric nuclear matter with Skyrme interactions.

Abstract

The speed of sound v is calculated for asymmetric nuclear matter within the general framework of a finite temperature Green's function method with normal pair cutoff approximation and Skyrme interactions. A rather strong dependence of v on \ensuremath{\alpha}, the asymmetry coefficient, is observed at high density. Causal violation of v at high density and/or high temperature is studied. This violation may be avoided if the Skyrme interaction parameters at high density may be readjusted to obey the conditions -1<d<0, ${t}_{3}$(3-${\ensuremath{\alpha}}^{2}$-2${\ensuremath{\alpha}}^{2}$${\ensuremath{\chi}}_{3}$)\ensuremath{\ge}0, and -1d0,${\mathit{t}}_{3}$(3-${\mathrm{\ensuremath{\alpha}}}^{2}$-2${\mathrm{\ensuremath{\alpha}}}^{2}$${\mathrm{\ensuremath{\chi}}}_{3}$)\ensuremath{\ge}0, and [(3${\mathit{t}}_{1}$+5${\mathit{t}}_{2}$)\ifmmode\pm\else\textpm\fi{}\ensuremath{\alpha}(${\mathit{t}}_{2}$-${\mathit{t}}_{1}$)]\ensuremath{\le}O. Implications of these