论文标题
部分可观测时空混沌系统的无模型预测
The BKT Transition and its Dynamics in a Spin Fluid
论文作者
论文摘要
我们研究颗粒迁移率对二维自旋流体中相变的影响。 BKT通用类别的相变的存在显示在具有计算机模拟的纯粹反相互作用的颗粒的非晶格模型中。一个关键的自旋波区域$ 0 <t <t _ {\ textrm {bkt}} $，与BKT理论所建议的形状遵循的非大学指数$η（t）$一起发现，其中包括与$η_ {\ textrm {bkt}} = 1/4 $ $ n _ {\ textrm {bkt}} = 1/4 $ $。人们可以在过渡温度$ t _ {\ textrm {bkt}} $上观察到从幂律衰减到指数衰减的过渡，该函数由有限大小的扩展分析支持。提出了一个临界温度$ t _ {\ textrm {bkt}} = 0.17（1）$。对相变的动态方面进行了研究。不一致的自旋自相关函数的短时行为与尼尔森 - 法派的预测一致，而长期行为与静态XY模型已知的有限尺寸缩放量不同。对相干自旋波动力学的分析表明，自旋波峰是一种传播模式，可以通过流体动力学理论合理地拟合。粒子的迁移率强烈增强了自旋波的阻尼，但该模型仍位于标准XY模型的动态普遍性类别中。
We study the effect of particle mobility on phase transitions in a spin fluid in two dimensions. The presence of a phase transition of the BKT universality class is shown in an off-lattice model of particles with purely repulsive interaction employing computer simulations. A critical spin wave region $0 < T < T_{\textrm{BKT}}$ is found with a non-universal exponent $η(T)$ that follows the shape suggested by BKT theory, including a critical value consistent with $η_{\textrm{BKT}} = 1/4$. One can observe a transition from power-law decay to exponential decay in the static correlation functions at the transition temperature $T_{\textrm{BKT}}$, which is supported by finite-size scaling analysis. A critical temperature $T_{\textrm{BKT}} = 0.17(1)$ is suggested. Investigations into the dynamic aspects of the phase transition are carried out. The short-time behavior of the incoherent spin autocorrelation function agrees with the Nelson-Fisher prediction, whereas the long-time behavior differs from the finite-size scaling known for the static XY model. Analysis of coherent spin wave dynamics shows that the spin wave peak is a propagating mode that can be reasonably well fitted by hydrodynamic theory. The mobility of the particles strongly enhances damping of the spin waves, but the model lies still within the dynamic universality class of the standard XY model.
