Speed of sound in asymmetric nuclear matter with Skyrme interactions

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 α, 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-${\alpha }^2$-2${\alpha }^2$ ${\chi }_3$)≥0, and -1d${\mathit{t}}_3$(3-${\mathrm{\alpha }}^2$-2${\mathrm{\alpha }}^2$ ${\mathrm{\chi }}_3$)≥0, and [(3${\mathit{t}}_1$+5${\mathit{t}}_2$)±α(${\mathit{t}}_2$-${\mathit{t}}_1$)]≤O. Implications of these