Ensemble inequivalence in the ferromagnetic p-spin model in random fields
Ensemble inequivalence in the ferromagnetic p-spin model in random fields
复制标题
随机场中铁磁 p-自旋模型的系综不等式
DOI：
10.1088/1742-5468/2011/01/p01016
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Y. Matsuda and H. Nishimori
中科院分区：
文献类型：
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作者：
Z. Bertalan;T. Kuma;Y. Matsuda and H. Nishimori
利用具有p体相互作用的铁磁伊辛模型研究了随机性对长程相互作用系统的影响。p= 2的情况下产生的相图类似于以前研究的模型，并显示已知的功能，正则和微正则系综的不等价性带来的，例如在一个狭窄的区域的相图负比热。然而，当p> 2时，正则相图与微正则相图完全不同。温度不一定唯一地确定微正则相，因此铁磁相和顺磁相在以温度和场强为轴绘制的常规相图的这种区域中不分离。低于一定值的外场强度，部分铁磁相具有负比热。对于较大的外场强度值的遍历性被打破之前的相变发生p> 2。此外，对于p> 2，麦克斯韦结构不能以一致的方式导出，因此，与先前具有负比热的情况相反，麦克斯韦结构不能桥接系综之间的差距。
We study the effect that randomness has on long-range interacting systems by using the ferromagnetic Ising model with p-body interactions in random fields. The case with p= 2 yields a phase diagram similar to that of previously studied models and shows known features that the inequivalence of the canonical and microcanonical ensembles brings with it, for example negative specific heat in a narrow region of the phase diagram. When p> 2, however, the canonical phase diagram is completely different from the microcanonical one. The temperature does not necessarily determine the microcanonical phases uniquely, and thus the ferromagnetic and paramagnetic phases are not separated in such a region of a conventional phase diagram drawn with the temperature and field strength as the axes. Below a certain value of the external field strength, part of the ferromagnetic phase has negative specific heat. For large values of the external field strength the ergodicity is broken before the phase transition occurs for p> 2. Moreover, for p> 2, the Maxwell construction cannot be derived in a consistent manner and therefore, in contrast to previous cases with negative specific heat, the Maxwell construction does not bridge the gap between the ensembles.