Diffeomorphism

Flow on a manifold

Let 𝑀 be a 𝐢𝛼-manifold with group of diffeomorphisms Aut𝛼⁑(𝑀). A (local) 1-parameter group πœ‘? :ℝ β†’Aut𝛼⁑(𝑀) is called a (local) flow on 𝑀. diff The orbit of a point 𝑝 βˆˆπ‘€ defines a 𝐢𝛼-curve

𝛾=πœ‘?(𝑝):(πœ–βˆ’,πœ–+)→𝑀

with 𝛾(0) =𝑝. The map

𝑝↦˙𝛾(0)=ddπ‘‘πœ‘π‘‘(𝑝)βˆ£π‘‘=0

defines a 𝐢𝛼-vector field π‘£π‘Ž βˆˆπ”›(𝑀), called the infinitesimal generator of πœ‘?.

Conversely, given a vector field π‘£π‘Ž βˆˆπ”›(𝑀), one can (usually) find a corresponding local flow whose orbits are called integral curves.


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