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arXiv 1111.0266cond-mat.dis-nncond-mat.stat-mech
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无序自旋系统中崎岖的自由能景观

Rugged free-energy landscapes in disordered spin systems

D. Yllanes

摘要:

本论文试图从计算的角度对复杂系统进行新的展望,并对某些模型给出物理答案。我们集中讨论了无序系统,解决了三维空间中的两个传统问题:爱德华-安德森自旋玻璃和场中的稀释反铁磁体(随机场伊辛模型的物理实现)。这些系统已通过大规模蒙特卡罗模拟进行了研究,利用各种平台,其中包括Janus专用超级计算机。两个主要主题是探讨整个:a)(实验无法达到)平衡相和非平衡演化之间的关系和b)的计算和有效的治疗崎岖的自由能景观。我们对D=3的Edwards-Anderson自旋玻璃的低温相进行了深入的研究,建立了一个时间长度字典和一个有限时间标度形式,以定量的方式将实验非平衡态和有限尺寸的平衡相联系起来.在实验相关的尺度上,复本对称性破缺理论作为合适的理论图像出现。我们还介绍了系留蒙特卡罗,一个一般的策略,系统的研究与崎岖的自由能景观。这种形式主义提供了一个通用的方法来指导探索的配置空间,通过约束一个或多个反应坐标。从这些系留模拟,亥姆霍兹势与反应坐标的重建,产生所有的信息系统。我们使用这种方法提供了一个全面的图片中的稀释反铁磁体的领域的临界行为。

英文摘要:

This thesis is an attempt to provide a new outlook on complex systems, as well as some physical answers for certain models, taking a computational approach. We have focused on disordered systems, addressing two traditional problems in three spatial dimensions: the Edwards-Anderson spin glass and the Diluted Antiferromagnet in a Field (the physical realisation of the random-field Ising model). These systems have been studied by means of large-scale Monte Carlo simulations, exploiting a variety of platforms, which include the Janus special-purpose supercomputer. Two main themes are explored throughout: a) the relationship between the (experimentally unreachable) equilibrium phase and the non-equilibrium evolution and b) the computation and efficient treatment of rugged free-energy landscapes. We perform a thorough study of the low-temperature phase of the D=3 Edwards-Anderson spin glass, where we establish a time-length dictionary and a finite-time scaling formalism to link, in a quantitative way, the experimental non-equilibrium regime and the finite-size equilibrium phase. At the experimentally relevant scales, the replica symmetry breaking theory emerges as the appropriate theoretical picture. We also introduce Tethered Monte Carlo, a general strategy for the study of systems with rugged free-energy landscapes. This formalism provides a general method to guide the exploration of the configuration space by constraining one or more reaction coordinates. From these tethered simulations, the Helmholtz potential associated to the reaction coordinates is reconstructed, yielding all the information about the system. We use this method to provide a comprehensive picture of the critical behaviour in the Diluted Antiferromagnet in a Field.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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