论文标题

部分可观测时空混沌系统的无模型预测

Disentangling Growth and Decay of Domains During Phase Ordering

论文作者

Majumder, Suman

论文摘要

储层计算是预测湍流的有力工具,其简单的架构具有处理大型系统的计算效率。然而,其实现通常需要完整的状态向量测量和系统非线性知识。我们使用非线性投影函数将系统测量扩展到高维空间,然后将其输入到储层中以获得预测。我们展示了这种储层计算网络在时空混沌系统上的应用,该系统模拟了湍流的若干特征。我们表明,使用径向基函数作为非线性投影器,即使只有部分观测并且不知道控制方程,也能稳健地捕捉复杂的系统非线性。最后,我们表明,当测量稀疏、不完整且带有噪声,甚至控制方程变得不准确时,我们的网络仍然可以产生相当准确的预测,从而为实际湍流系统的无模型预测铺平了道路。

Using Monte Carlo simulations we study the phase ordering dynamics of a \textit{multi}-species system modeled via the prototype $q$-state Potts model. In such a \textit{multi}-species system, we identify a spin states or species as the \textit{winner} if it has survived as the majority in the final state, otherwise we mark them as \textit{loser}. We disentangle the time ($t$) dependence of the domain length of the \textit{winner} from \textit{losers}, rather than monitoring the average domain length obtained by treating all spin states or species alike. The kinetics of domain growth of the \textit{winner} at a finite temperature in space dimension $d=2$ reveal that the expected Lifshitz-Cahn-Allen scaling law $\sim t^{1/2}$ can be observed with no early-time corrections, even for system sizes much smaller than what is traditionally used. Up to a certain period, all the others species, i.e., the \textit{losers}, also show a growth that, however, is dependent on the total number of species, and slower than the expected $\sim t^{1/2}$ growth. Afterwards, the domains of the \textit{losers} start decaying with time, for which our data strongly suggest the behavior $\sim t^{-z}$, where $z=2$ is the dynamical exponent for nonconserved dynamics. We also demonstrate that this new approach of looking into the kinetics also provides new insights for the special case of phase ordering at zero temperature, both in $d=2$ and $d=3$.

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