标题： 接近QCD临界点的转变线上的非单调比熵 显示英文标题

标题： Nonmonotonic specific entropy on the transition line near the QCD critical point

摘要： 我们研究了量子色动力学（QCD）临界点对QCD相图中等熵轨迹的影响。 我们指出，临界状态方程的普适性和热力学第三定律要求共存线（一阶相变线）上的每单位重子的比熵至少在一侧是非单调的。 具体来说，必须存在一个极大值。 我们展示了临界状态方程中常用的参数如何影响该极大值相对于QCD临界点的位置。 然后，我们检查了绝热膨胀的重离子碰撞火球在临界点附近的等熵轨迹行为。 我们发现，在临界点处压力的等容温度导数的符号起到了关键作用；这一符号决定了比熵在哪一侧必须是非单调的（即具有极大值）。 我们根据判别参数的值和轨迹接近临界点的程度，分类了绝热膨胀的不同情形。 显示英文摘要

摘要： We investigate the effect of the quantum chromodynamics (QCD) critical point on the isentropic trajectories in the QCD phase diagram. We point out that the universality of the critical equation of state and the third law of thermodynamics require the specific entropy (per baryon) along the coexistence (first-order transition) line to be nonmonotonic at least on one side of that line. Specifically, a maximum must occur. We show how the location of the maximum relative to the QCD critical point depends on the parameters of the critical equation of state commonly used in the literature. We then examine how the isentropic trajectories followed by adiabatically expanding heavy-ion collision fireballs behave near the critical point. We find that a crucial role is played by the sign of the isochoric temperature derivative of pressure at the critical point; this sign determines on which side of the coexistence curve the specific entropy must be nonmonotonic (i.e., has a maximum). We classify different scenarios of the adiabatic expansion that arise depending on the value of the discriminant parameter and the proximity of the trajectory to the critical point.