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奇数阶净重子数广义磁化率临界行为的研究

Critical Behavior of Odd-order Generalized Susceptibilities of Net Baryon Number

  • 摘要: 本文基于临界行为的普适性,假设量子色动力学(Quantum Chromodynamics, QCD)系统达到热平衡状态,将三维伊辛模型变量映射到QCD相平面,研究了净重子数五阶、七阶和九阶广义磁化率在相平面上的密度分布,及其沿着化学冻结线的净重子化学势依赖性。当只考虑伊辛模型中领头阶临界贡献时,从低净重子化学势区域趋近于临界点,各阶磁化率均出现负的凹陷后面紧接着正的峰的结构。而当加入次领头阶临界贡献时,负的凹陷是否存在依赖于化学冻结线到相边界的距离和临界区域标度指数的大小,但正峰结构一直存在,不受这些因素的影响。与负的凹陷相比,正峰结构可作为临界点的一个更稳定的特征。

     

    Abstract: Assuming that the Quantum Chromodynamics (QCD) system reaches a state of thermal equilibrium, based on the universality of critical behavior, by mapping the variables of the three-dimensional Ising model onto the QCD phase plane, we investigate the density distributions of fifth-, seventh-, and ninth-order generalized susceptibilities of the net baryon number on the phase plane, as well as their dependence on the net-baryon chemical potential along the chemical freeze-out line. When only the leading-order critical contribution from the Ising model is considered, approaching the critical point from the low net-baryon chemical potential region, the generalized susceptibilities all exhibit a structure characterized by a negative dip followed by a positive peak. Upon incorporating the next-leading-order critical contribution, the presence of the negative dip becomes dependent on the distance to the phase boundary and the scaling parameters corresponding to the critical region. However, the positive peak structure remains consistently present and unaffected by these factors. In comparison to the negative dip, the positive peak structure can be considered a more robust feature indicative of the critical point.

     

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