论文标题
非线性磁性超材料的分数动力学
Fractional dynamics in nonlinear magnetic metamaterials
论文作者
论文摘要
我们使用laplacian在进化方程中的分数扩展,在分裂谐振器的阵列中检查了非线性模式及其时间动力学的存在。我们发现分散关系的封闭形式表达是分数指数的函数,以及环之间的临界耦合的精确表达,除此之外,不存在分数磁电感波。我们还发现了散装和表面非线性模式的低洼家族及其分叉图。在这里,现象学对所有指数都相似,并且类似于其他离散演化方程(例如DNL)中观察到的内容。最初局部磁激发的传播始终是弹道的,其速度是按精确形式计算为分数指数的函数的。对于给定的指数,它随着耦合的增加到关键的耦合值而增加,除此之外,弹道速度可能会在分数间隔$ [0,1] $内部差异。调节不稳定性的检查表明,它倾向于随着分数指数的增加而增加,在这种情况下,衰减是通过形成最终合并并形成纯辐射的丝状结构进行的。最初局部激发周围的动态自我捕获会随着分数指数的增加而增加,但它也显示出一定程度的诱捕线性限制。这种陷阱随着指数的减少而增加,可以通过几乎依赖性的考虑来解释。
We examine the existence of nonlinear modes and their temporal dynamics, in arrays of split-ring resonators, using a fractional extension of the Laplacian in the evolution equation. We find a closed-form expression for the dispersion relation as a function of the fractional exponent as well as an exact expression for the critical coupling between rings, beyond which no fractional magnetoinductive wave can exist. We also find the low-lying families of bulk and surface nonlinear modes and their bifurcation diagrams. Here the phenomenology is similar for all exponents and resembles what has been observed in other discrete evolution equations, such as the DNLS. The propagation of an initially localized magnetic excitation is always ballistic, with a `speed' that is computed in exact form as a function of the fractional exponent. For a given exponent, it increases with an increase in coupling up to a critical coupling value, beyond which the ballistic speed could diverge inside the fractional interval $[0,1]$. Examination of the modulational instability shows that it tends to increase with an increase in the fractional exponent, where the decay proceeds via the formation of filamentary structures that merge eventually and form pure radiation. The dynamical selftrapping around an initially localized excitation increases with the fractional exponent, but it also shows a degree of trapping in the linear limit. This trapping increases with a decrease in the exponent and can be explained by near-degeneracy considerations.