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有限温下的奇异滴

Strangelets at Finite Temperature

  • 摘要: 在等效质量模型的框架下,考虑线性禁闭和一阶微扰相互作用的贡献,研究了有限温度情形下奇异滴的各种性质。通过在坐标空间数值求解夸克的狄拉克方程,能够估算奇异滴的壳效应。随着温度升高,根据费米-狄拉克统计原理,夸克更容易占据能量更高的能级,此时壳效应减弱,即壳衰减现象。令人意外的是,从液滴模型公式中得出的表面张力并没有随着温度的升高而降低,而是升高,并在温度T \approx 20 \sim 40 \; \rmMeV到达峰值。在这个温度下,壳修正变得可以忽略不计,液滴模型公式为奇异滴的每重子自由能提供了一个合理的近似值。然而,曲率项似乎并不受壳修正影响,而是随着温度升高而单调减少。还计算了奇异滴的核子发射率随温度的变化。对于稳定的奇异滴,核子发射率随温度的升高而增加,而对于不稳定的奇异滴则相反。最后还计算了有限温度下奇异滴的其他性质。相关计算结果将有助于人们理解双致密星并合和重离子碰撞的产物。

     

    Abstract: We study the properties of strangelets at finite temperature T, employing an equivparticle model that incorporates both linear confinement and leading-order perturbative interactions with density-dependent quark masses. The shell effects are analyzed by solving the Dirac equations for quarks within the mean-field approximation. As temperature increases, these effects weaken due to the occupation probability of single-particle levels being governed by the Fermi-Dirac statistics, a phenomenon known as shell dampening. Surprisingly, the surface tension, derived from a liquid-drop formula, does not decrease with temperature but instead rises until it peaks at T \approx 20 \sim 40 MeV. At this temperature, shell corrections become negligible, and the formula provides a reasonable approximation for the free energy per baryon of strangelets. However, the curvature term decreases with T despite the presence of shell effects. The neutron and proton emission rates are determined microscopically by the external nucleon gas densities that are in equilibrium with strangelets. These emission rate generally increases with T for stable strangelets, but decrease for those that are unstable to nucleon emission at T = 0. The other properties of β-stable strangelets obtained with various parameter sets are presented as well. The results indicated in this work are useful for understanding the products of binary compact star mergers and heavy-ion collisions.

     

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