Liquid-gas phase transition in nuclear matter including strangeness

We apply the chiral SU(3) quark mean field model to study the properties of strange hadronic matter at finite temperature. The liquid-gas phase transition is studied as a function of the strangeness fraction. The pressure of the system cannot remain constant during the phase transition, since there are two independent conserved charges (baryon and strangeness number). In a range of temperatures around $15\mathrm{MeV}$ (precise values depending on the model used) the equation of state exhibits multiple bifurcates. The difference in the strangeness fraction $f_s$ between the liquid and gas phases is small when they coexist. The critical temperature of strange matter turns out to be a nontrivial function of the strangeness fraction.

Figure 1

The pressure of strange hadronic matter $p$ versus baryon density ${\rho }_B$ with different strangeness fractions $f_s$ at temperature $T=15\mathrm{MeV}$ in the case of the square root ansatz of effective baryon mass.

Figure 2

The pressure of strange hadronic matter $p$ versus baryon density ${\rho }_B$ with different strangeness fractions $f_s$ at temperature $T=15\mathrm{MeV}$ in the case of the linear definition of effective baryon mass.

Figure 3

Geometrical construction used to obtain the chemical potentials and strangeness fractions in the two-phase coexistence at temperature $T=15\mathrm{MeV}$ and $p=0.23\mathrm{MeV}{\mathrm{fm}}^{-3}$. The solid and dashed lines are for the nucleon and $\Lambda$, respectively.

Figure 4

Geometrical construction used to obtain the chemical potentials and strangeness fractions in the two-phase coexistence at temperature $T=15\mathrm{MeV}$ and $p=0.27\mathrm{MeV}{\mathrm{fm}}^{-3}$. The solid and dashed lines are for the nucleon and $\Lambda$, respectively.

Figure 5

The first binodal curve with smaller strangeness fraction at temperature $T=15\mathrm{MeV}$. The points $a$ through $d$ denote the liquid-gas phase transition. $A$ is the critical point.

Figure 6

The second binodal curve with larger strangeness fraction at temperature $T=15\mathrm{MeV}$. $B$ and $C$ are the critical points.

Figure 7

The critical temperature $T_c$ versus strangeness fraction $f_s$. The solid and dashed lines correspond to the square root and linear case, respectively.