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arXiv 0907.0354math.DS
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向量场的重参数化及其移位映射

Reparametrizations of vector fields and their shift maps

Sergiy Maksymenko

摘要:

设$M$是光滑流形,$F$是$M$上的光滑向量场,$F_t$是$F$的局部流.用$Sh(F)$表示具有以下形式的光滑映射$h:M\to M$的空间:$h(x) = F_{f(x)}(x)$,其中$f:M\to\mathbb{R}$在$M$上的所有光滑函数上运行,这些光滑函数可以被代入流$F_t$而不是时间。这个空间经常与保持$F$轨道的同构群的单位分量重合。本文证明了$Sh(F)$在$F$的重新参数化和前推下不发生变化。作为应用,证明了无非闭轨道的向量场$F$可以重新参数化,从而在$M$上诱导圆作用当且仅当存在光滑函数$f:M\to (0,+\infty)$,使得对于$M$的每个非奇异点$x$,值$f(x)$是$x$关于$F$的周期的整数倍.

英文摘要:

Let $M$ be a smooth manifold, $F$ be a smooth vector field on $M$, and $F_t$ be the local flow of $F$. Denote by $Sh(F)$ the space of smooth maps $h:M\to M$ of the following form: $h(x) = F_{f(x)}(x)$, where $f:M\to\mathbb{R}$ runs over all smooth functions on $M$ which can be substituted into the flow $F_t$ instead of time. This space often coincides with the identity component of the group of diffeomorphisms preserving orbits of $F$. In this note it is shown that $Sh(F)$ is not changed under reparametrizations and pushforwards of $F$. As an application it is proved that a vector field $F$ without non-closed orbits can be reparametrized to induce a circle action on $M$ if and only if there exists a smooth function $f:M\to (0,+\infty)$ such that for each non-singular point $x$ of $M$, the value $f(x)$ is an integer multiple of the period of $x$ with respect to $F$.

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