Transition from quasiperiodicity with many frequencies (i.e., a high-dimensional torus) to chaos is studied by using $N$-dimensional globally coupled circle maps. First, the existence of $N$-dimensional tori with $N\geq 2$ is confirmed while they become exponentially rare with $N$. Besides, chaos exists even when the map is invertible, and such chaos has more null Lyapunov exponents as $N$ increases. This unusual form of "chaos on a torus," termed toric chaos, exhibits delocalization and slow dynamics of the first Lyapunov vector. Fractalization of tori at the transition to chaos is also suggested. The relevance of toric chaos to neural dynamics and turbulence is discussed in relation to chaotic itinerancy.
Different routes to chaos via strange nonchaotic attractor in a quasiperiodically forced system
研究了一类拟周期受迫动力系统的奇异非混沌吸引子。几条路线，包括标准的奇怪的非混沌吸引子的外观发生，被证明是可实现的在同一模型中的两个参数（$f-ε$）域的系统。特别地，借助于双参数（$f-ε$）相图，证明了环面通过SNA从倍周期到混沌的转变，环面通过SNA从倍周期到混沌的破缺以及分形环面的倍周期分岔。更有趣的是，为了接近奇怪的非混沌吸引子，存在的几个新的分歧对应的环面鼓泡的新现象的环面进行了描述。特别指出了通向混沌的新途径：（1）双频准周期性$\to$环面加倍$\to$环面并合，然后环面逐步分形，（二）双频率准周期性$\to$环面加倍$\to$混沌$\to$ SNA $\to$混沌$\to$逆环面加倍$\to$环面$\to$环面开始后的环面气泡通过SNA打破混沌或随后通过SNA开始环面加倍路径进入混沌。通过计算系统的李雅普诺夫指数、缠绕数、功率谱测度和维数等特征量，证实了奇异非混沌吸引子的存在性.各种分叉背后的机制也进行了简要讨论。
Smooth and Non-Smooth Dependence of Lyapunov Vectors upon the Angle Variable on a Torus in the Context of Torus-Doubling Transitions in the Quasiperiodically Forced Henon Map
Interruption of torus doubling bifurcation and genesis of strange nonchaotic attractors in a quasiperiodically forced map : Mechanisms and their characterizations
