Condition on vector field to be a diffeomorphism.

[kroni]

Hi everybody,

Let V(x) a vector field on a manifold (R^2 in my case), i am looking for a condition on V(x) for which the function x^µ \rightarrow x^µ + V^µ(x) is a diffeomorphism. I read some document speaking about the flow, integral curve for ODE solving but i fail to find a generic condition to avoid V to send two point on the same coordinate. I think about the generator of the diffeomorphism group but it's only defined infinitesimaly.

Thanks

Clément

 

[wrobel]

there are a lot of possible approaches to sufficient conditions. For example, if $\sup_{x\in\mathbb{R}^2}\Big\|\frac{\partial V}{\partial x}\Big\|$ is small enough then it is a diffeomorphism. monotonicity assumption can also help. Perhaps the book Topics in Nonlinear Functional Analysis by L Nirenberg would be of use

 

[kroni]

Monotonicity work only in 1D,
\sup_{x\in\mathbb{R}^2}\Big\|\frac{\partial V}{\partial x}\Big\|[\itex] is non local.<br /> I will look in the book you advise. I find this problem really interesting, may be treated and treated again, but interesting<br /> <br /> Thanks for your answer.<br /> <br /> Clément

 

[wrobel]

Monotonicity work only in 1D,

there is multidimensional version of monotonicity, by the way:)