Submersion
In
mathematics, a differentiable map
f from an m-manifold
M to an n-manifold
N is called a
submersion if its differential
df is an onto map at every point
m of
M:
- rk df(m) = dim N.
Examples include the projections in smooth vector bundles; and more general smooth fibrations. Therefore one can regard the submersion condition as a necessary condition for a local trivialization to exist. There are some converse results.
The points at which f fails to be a submersion are the critical points of f: they are those at which the Jacobian matrix of f, with respect to local coordinates, is not of maximum rank. They are the basic objects of study in singularity theory; and also in Morse theory.
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