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Suppose that : is a smooth map between smooth manifolds; then the differential of at a point , denoted , is, in some sense, the best linear approximation of near . It can be viewed as a generalization of the total derivative of ordinary calculus.
Just as there are various types of manifolds, there are various types of maps of manifolds. PDIFF serves to relate DIFF and PL, and it is equivalent to PL.. In geometric topology, the basic types of maps correspond to various categories of manifolds: DIFF for smooth functions between differentiable manifolds, PL for piecewise linear functions between piecewise linear manifolds, and TOP for ...
Smooth maps between manifolds induce linear maps between tangent spaces: for :, at each point the pushforward (or differential) maps tangent vectors at to tangent vectors at (): ,: (), and on the level of the tangent bundle, the pushforward is a vector bundle homomorphism: :.
Let M and N be differentiable manifolds and : be a differentiable map between them. The map f is a submersion at a point if its differential: is a surjective linear map. [1] In this case p is called a regular point of the map f, otherwise, p is a critical point.
Many otherwise familiar examples of smooth manifolds, however, cannot be given a Lie group structure, since given a Lie group and any , one could consider the map (,): which sends the identity element to and hence, by considering the differential , gives a natural identification between any two tangent spaces of a Lie group.
A coordinate map, a coordinate chart, or simply a chart, of a manifold is an invertible map between a subset of the manifold and a simple space such that both the map and its inverse preserve the desired structure. [2]
When the map between manifolds is a diffeomorphism, that is, it has a smooth inverse, then pullback can be defined for the vector fields as well as for 1-forms, and thus, by extension, for an arbitrary mixed tensor field on the manifold.
A map is a local diffeomorphism if and only if it is a smooth immersion (smooth local embedding) and an open map. The inverse function theorem implies that a smooth map f : X → Y {\displaystyle f:X\to Y} is a local diffeomorphism if and only if the derivative D f x : T x X → T f ( x ) Y {\displaystyle Df_{x}:T_{x}X\to T_{f(x)}Y} is a linear ...