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arXiv 1004.0978math.AP
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周期性$μ$ -Degasperis-Procesi方程的几何性质

Geometric aspects of the periodic $μ$-Degasperis-Procesi equation

Joachim Escher, Martin Kohlmann, Boris Kolev

摘要:

我们考虑周期$\muDP$方程(Degasperis-Procesi方程的一个修改版本)作为一个右不变仿射联络$\nabla$在圆$§^1=\R/\Z$的所有光滑和保持方向的单同态的Fréchet李群$\Diff^{\infty}(§^1)$上的测地流.在$\Diff^{\infty}(§^1)$的李代数$\C^{\infty}(§^1)$上,这种联系是由李括号和一个双线性算子的和正则地给出的。对于光滑的初始数据,我们证明了$\muDP$的光滑解的短时存在性,它光滑地依赖于时间和初始数据。进一步证明了$\nabla$定义的指数映射是$\C^{\infty}(§^1)$中零的邻域到$\Diff^{\infty}(§^1)$中单位元的邻域上的光滑局部自同构.我们的结果遵循李群上的非度量Euler方程的一般方法,Fréchet空间$\C^{\infty}(§^1)$的巴拿赫空间近似,以及测地流的尖锐的空间正则性结果。

英文摘要:

We consider the periodic $\muDP$ equation (a modified version of the Degasperis-Procesi equation) as the geodesic flow of a right-invariant affine connection $\nabla$ on the Fréchet Lie group $\Diff^{\infty}(§^1)$ of all smooth and orientation-preserving diffeomorphisms of the circle $§^1=\R/\Z$. On the Lie algebra $\C^{\infty}(§^1)$ of $\Diff^{\infty}(§^1)$, this connection is canonically given by the sum of the Lie bracket and a bilinear operator. For smooth initial data, we show the short time existence of a smooth solution of $\muDP$ which depends smoothly on time and on the initial data. Furthermore, we prove that the exponential map defined by $\nabla$ is a smooth local diffeomorphism of a neighbourhood of zero in $\C^{\infty}(§^1)$ onto a neighbourhood of the unit element in $\Diff^{\infty}(§^1)$. Our results follow from a general approach on non-metric Euler equations on Lie groups, a Banach space approximation of the Fréchet space $\C^{\infty}(§^1)$, and a sharp spatial regularity result for the geodesic flow.

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